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Kavoosi M, O’Reilly TE, Kavoosi M, Chai P, Engel C, Korz W, Gallen CC, Lester RM. Safety, Tolerability, Pharmacokinetics, and Concentration-QTc Analysis of Tetrodotoxin: A Randomized, Dose Escalation Study in Healthy Adults. Toxins (Basel) 2020; 12:toxins12080511. [PMID: 32784930 PMCID: PMC7472037 DOI: 10.3390/toxins12080511] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 08/05/2020] [Accepted: 08/05/2020] [Indexed: 12/19/2022] Open
Abstract
Tetrodotoxin (TTX) is a highly specific voltage-gated sodium channel (VGSC) blocker in clinical evaluation as a peripheral-acting analgesic for chronic pain. This study presents the first published results of the safety including cardiac liability of TTX at therapeutic-relevant concentrations in twenty-five healthy adults. Randomized, double-blind, placebo-, and positive- (moxifloxacin) controlled study evaluated single ascending doses of 15 µg, 30 µg, and 45 µg TTX over 3 periods with a 7-day washout between each period. Subcutaneous injections of TTX were readily absorbed, reaching maximum plasma concentration (Cmax) within 1.5 h. Both extent of exposure (AUC) and Cmax increased in proportion to dose. No QT prolongation was identified by concentration-QTc analysis and the upper bounds of the two-sided 90% confidence interval of predicted maximum baseline and placebo corrected QTcF (ΔΔQTcF) value did not exceed 10 ms for all tetrodotoxin doses, thereby meeting the criteria of a negative QT study. Safety assessments showed no clinically relevant changes with values similar between all groups and no subject withdrawing due to adverse events. Paresthesia, oral-paresthesia, headache, dizziness, nausea, and myalgia were the most common TEAEs (overall occurrence ≥5%) in the TTX treatment groups. TTX doses investigated in this study are safe, well-tolerated, and lack proarrhythmic proclivity.
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Affiliation(s)
- Mojgan Kavoosi
- WEX Pharmaceuticals Inc., Vancouver, BC V6E-4A6, Canada; (M.K.); (W.K.); (C.C.G.)
- Correspondence:
| | | | - Mehran Kavoosi
- WEX Pharmaceuticals Inc., Vancouver, BC V6E-4A6, Canada; (M.K.); (W.K.); (C.C.G.)
| | - Peng Chai
- Celerion Inc., Lincoln, NE 68502, USA;
| | | | - Walter Korz
- WEX Pharmaceuticals Inc., Vancouver, BC V6E-4A6, Canada; (M.K.); (W.K.); (C.C.G.)
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Boente-Juncal A, Otero P, Rodríguez I, Camiña M, Rodriguez-Vieytes M, Vale C, Botana LM. Oral Chronic Toxicity of the Safe Tetrodotoxin Dose Proposed by the European Food Safety Authority and Its Additive Effect with Saxitoxin. Toxins (Basel) 2020; 12:E312. [PMID: 32397553 PMCID: PMC7291010 DOI: 10.3390/toxins12050312] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/06/2020] [Accepted: 05/07/2020] [Indexed: 12/25/2022] Open
Abstract
Tetrodotoxin (TTX) is a potent natural toxin causative of human food intoxications that shares its mechanism of action with the paralytic shellfish toxin saxitoxin (STX). Both toxins act as potent blockers of voltage-gated sodium channels. Although human intoxications by TTX were initially described in Japan, nowadays increasing concern about the regulation of this toxin in Europe has emerged due to its detection in fish and mollusks captured in European waters. Currently, TTX is only regularly monitored in Dutch fishery products. However, the European Food Safety Authority (EFSA) has established a safety level of 44 µg/kg TTX as the amount of toxin that did not cause adverse effects in humans. This level was extrapolated considering initial data on its acute oral toxicity and EFSA remarked the need for chronic toxicity studies to further reduce the uncertainty of future toxin regulations. Thus, in this work, we evaluated the oral chronic toxicity of TTX using the safety levels initially recommended by EFSA in order to exclude potential human health risks associated with the worldwide expanding presence of TTX. Using internationally recommended guidelines for the assessment of oral chronic toxicity, the data provided here support the proposed safety level for TTX as low enough to prevent human adverse effects of TTX even after chronic daily exposure to the toxin. However, the combination of TTX with STX at doses above the maximal exposure level of 5.3 µg/kg body weight derived by EFSA increased the lethality of TTX, thus confirming that both TTX and paralytic shellfish toxins should be taken into account to assess human health risks.
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Affiliation(s)
- Andrea Boente-Juncal
- Laboratorio de Farmacología, Farmacia e Tecnoloxía Farmacéutica, Universidade de Santiago de Compostela, Facultad de Veterinaria, Campus Universitario s/n, 27002 Lugo, Spain; (A.B.-J.); (P.O.)
| | - Paz Otero
- Laboratorio de Farmacología, Farmacia e Tecnoloxía Farmacéutica, Universidade de Santiago de Compostela, Facultad de Veterinaria, Campus Universitario s/n, 27002 Lugo, Spain; (A.B.-J.); (P.O.)
| | - Inés Rodríguez
- Laboratorios Cifga, Benigno Rivera, 56, 27003 Lugo, Spain;
| | - Mercedes Camiña
- Departamento de Fisiología, Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002 Lugo, Spain; (M.C.); (M.R.-V.)
| | - Mercedes Rodriguez-Vieytes
- Departamento de Fisiología, Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002 Lugo, Spain; (M.C.); (M.R.-V.)
| | - Carmen Vale
- Laboratorio de Farmacología, Farmacia e Tecnoloxía Farmacéutica, Universidade de Santiago de Compostela, Facultad de Veterinaria, Campus Universitario s/n, 27002 Lugo, Spain; (A.B.-J.); (P.O.)
| | - Luis M. Botana
- Laboratorio de Farmacología, Farmacia e Tecnoloxía Farmacéutica, Universidade de Santiago de Compostela, Facultad de Veterinaria, Campus Universitario s/n, 27002 Lugo, Spain; (A.B.-J.); (P.O.)
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Hong B, He J, Le Q, Bai K, Chen Y, Huang W. Combination Formulation of Tetrodotoxin and Lidocaine as a Potential Therapy for Severe Arrhythmias. Mar Drugs 2019; 17:md17120685. [PMID: 31817438 PMCID: PMC6949965 DOI: 10.3390/md17120685] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 11/30/2019] [Accepted: 12/03/2019] [Indexed: 11/16/2022] Open
Abstract
Severe arrhythmias-such as ventricular arrhythmias-can be fatal, but treatment options are limited. The effects of a combined formulation of tetrodotoxin (TTX) and lidocaine (LID) on severe arrhythmias were studied. Patch clamp recording data showed that the combination of LID and TTX had a stronger inhibitory effect on voltage-gated sodium channel 1.5 (Nav1.5) than that of either TTX or LID alone. LID + TTX formulations were prepared with optimal stability containing 1 μg of TTX, 5 mg of LID, 6 mg of mannitol, and 4 mg of dextran-40 and then freeze dried. This formulation significantly delayed the onset and shortened the duration of arrhythmia induced by aconitine in rats. Arrhythmia-originated death was avoided by the combined formulation, with a decrease in the mortality rate from 64% to 0%. The data also suggests that the anti-arrhythmic effect of the combination was greater than that of either TTX or LID alone. This paper offers new approaches to develop effective medications against arrhythmias.
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Affiliation(s)
- Bihong Hong
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; (J.H.); (Q.L.); (K.B.); (Y.C.); (W.H.)
- Technical Innovation Center for Utilization of Marine Biological Resources, Ministry of Natural Resources, Xiamen 361005, China
- Correspondence: ; Tel.: +86-0592-2195265
| | - Jianlin He
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; (J.H.); (Q.L.); (K.B.); (Y.C.); (W.H.)
- Technical Innovation Center for Utilization of Marine Biological Resources, Ministry of Natural Resources, Xiamen 361005, China
| | - Qingqing Le
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; (J.H.); (Q.L.); (K.B.); (Y.C.); (W.H.)
- Technical Innovation Center for Utilization of Marine Biological Resources, Ministry of Natural Resources, Xiamen 361005, China
| | - Kaikai Bai
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; (J.H.); (Q.L.); (K.B.); (Y.C.); (W.H.)
- Technical Innovation Center for Utilization of Marine Biological Resources, Ministry of Natural Resources, Xiamen 361005, China
| | - Yongqiang Chen
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; (J.H.); (Q.L.); (K.B.); (Y.C.); (W.H.)
- College of Food and Biological Engineering, Jimei University, Xiamen 361021, China
| | - Wenwen Huang
- Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China; (J.H.); (Q.L.); (K.B.); (Y.C.); (W.H.)
- Technical Innovation Center for Utilization of Marine Biological Resources, Ministry of Natural Resources, Xiamen 361005, China
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Shomorony A, Santamaria CM, Zhao C, Rwei AY, Mehta M, Zurakowski D, Kohane DS. Prolonged Duration Local Anesthesia by Combined Delivery of Capsaicin- and Tetrodotoxin-Loaded Liposomes. Anesth Analg 2019; 129:709-717. [PMID: 31425210 DOI: 10.1213/ane.0000000000004108] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Capsaicin, the active component of chili peppers, can produce sensory-selective peripheral nerve blockade. Coadministration of capsaicin and tetrodotoxin, a site-1 sodium channel blocker, can achieve a synergistic effect on duration of nerve blocks. However, capsaicin can be neurotoxic, and tetrodotoxin can cause systemic toxicity. We evaluated whether codelivery of capsaicin and tetrodotoxin liposomes can achieve prolonged local anesthesia without local or systemic toxicity. METHODS Capsaicin- and tetrodotoxin-loaded liposomes were developed. Male Sprague-Dawley rats were injected at the sciatic nerve with free capsaicin, capsaicin liposomes, free tetrodotoxin, tetrodotoxin liposomes, and blank liposomes, singly or in combination. Sensory and motor nerve blocks were assessed by a modified hotplate test and a weight-bearing test, respectively. Local toxicity was assessed by histologic scoring of tissues at the injection sites and transmission electron microscopic examination of the sciatic nerves. Systemic toxicity was assessed by rates of contralateral nerve deficits and/or mortality. RESULTS The combination of capsaicin liposomes and tetrodotoxin liposomes achieved a mean duration of sensory block of 18.2 hours (3.8 hours) [mean (SD)], far longer than that from capsaicin liposomes [0.4 hours (0.5 hours)] (P < .001) or tetrodotoxin liposomes [0.4 hours (0.7 hours)] (P < .001) given separately with or without the second drug in free solution. This combination caused minimal myotoxicity and muscle inflammation, and there were no changes in the percentage or diameter of unmyelinated axons. There was no systemic toxicity. CONCLUSIONS The combination of encapsulated tetrodotoxin and capsaicin achieved marked prolongation of nerve block. This combination did not cause detectable local or systemic toxicity. Capsaicin may be useful for its synergistic effects on other formulations even when used in very small, safe quantities.
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Affiliation(s)
- Andre Shomorony
- From the Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Department of Anesthesiology, Boston Children's Hospital, Boston, Massachusetts
| | - Claudia M Santamaria
- From the Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Department of Anesthesiology, Boston Children's Hospital, Boston, Massachusetts
| | - Chao Zhao
- From the Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Department of Anesthesiology, Boston Children's Hospital, Boston, Massachusetts
| | - Alina Y Rwei
- From the Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Department of Anesthesiology, Boston Children's Hospital, Boston, Massachusetts
| | - Manisha Mehta
- From the Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Department of Anesthesiology, Boston Children's Hospital, Boston, Massachusetts
| | - David Zurakowski
- Department of Anesthesiology, Perioperative, and Pain Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Daniel S Kohane
- From the Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Department of Anesthesiology, Boston Children's Hospital, Boston, Massachusetts
- Department of Anesthesiology, Perioperative, and Pain Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
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Finch SC, Boundy MJ, Harwood DT. The Acute Toxicity of Tetrodotoxin and Tetrodotoxin⁻Saxitoxin Mixtures to Mice by Various Routes of Administration. Toxins (Basel) 2018; 10:E423. [PMID: 30360529 PMCID: PMC6266834 DOI: 10.3390/toxins10110423] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 10/19/2018] [Accepted: 10/19/2018] [Indexed: 01/14/2023] Open
Abstract
Tetrodotoxin (TTX) is a potent neurotoxin associated with human poisonings through the consumption of pufferfish. More recently, TTX has been identified in bivalve molluscs from diverse geographical environments, including Europe, and is therefore recognised as an emerging threat to food safety. A recent scientific opinion of the EFSA Panel on Contaminants in the Food Chain recognised the need for further data on the acute oral toxicity of TTX and suggested that, since saxitoxin (STX) and TTX had similar modes of action, it was possible that their toxicities were additive so could perhaps be combined to yield one health-based guideline value. The present study determined the toxicity of TTX by various routes of administration. The testing of three different mixtures of STX and TTX and comparing the experimentally determined values to those predicted on the basis of additive toxicity demonstrated that the toxicities of STX and TTX are additive. This illustrates that it is appropriate to treat TTX as a member of the paralytic shellfish group of toxins. Since the toxicity of TTX was found to be the same as STX by feeding, a molar toxicity equivalence factor of 1.0 for TTX can be applied.
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Affiliation(s)
- Sarah C Finch
- AgResearch Limited, Ruakura Research Centre, Private Bag 3123, Hamilton 3240, New Zealand.
| | | | - D Tim Harwood
- Cawthron Institute, Private Bag 2, Nelson 7042, New Zealand.
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6
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Nishide S, Honma S, Honma KI. Two coupled circadian oscillations regulate Bmal1-ELuc and Per2-SLR2 expression in the mouse suprachiasmatic nucleus. Sci Rep 2018; 8:14765. [PMID: 30283092 PMCID: PMC6170461 DOI: 10.1038/s41598-018-32516-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 08/01/2018] [Indexed: 11/08/2022] Open
Abstract
Circadian rhythms in clock genes, Bmal1 and Per2 expression were monitored simultaneously in the cultured slice of mouse suprachiasmatic nucleus (SCN) by dual bioluminescent reporters. In the neonatal SCN, the phase-relation between the Bmal1 and Per2 rhythms were significantly changed during culture. Medium exchange produced phase-dependent phase shifts (PRCm) in the Bmal1 rhythms, but not in the Per2 rhythms. As a result, the two circadian rhythms were temporally dissociated after medium exchange. In the adult SCN, the phase-relation between the two rhythms was kept constant during culture at least up to 20 cycles. The amplitude of PRCm in the adult SCN was significantly attenuated in the Bmal1 rhythm, whereas a PRCm was developed in the Per2 rhythm. The circadian period was not systematically affected by medium exchange in either of rhythms, regardless of whether it was in the neonatal or the adult SCN. Tetrodotoxin, a sodium channel blocker, enhanced the phase-response in both rhythms but abolished the phase-dependency. In addition, tetrodotoxin lengthened the circadian period independent of the phase of administration. Thus, the Bmal1 and Per2 rhythms in the SCN are dissociable and likely regulated by distinct circadian oscillators. Bmal1 is the component of a Bmal1/REV-ERBa/ROR loop and Per2 a Per/Cry/BMAL1/CLOCK loop. Both loops could be molecular mechanisms of the two circadian oscillators that are coupled through the protein product of Bmal1. The coupling strength between the two oscillations depends on developmental stages.
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Affiliation(s)
- Shinya Nishide
- Department of Physiology, Faculty of Medicine, Hokkaido University, Hokkaido, Japan
- Department of Occupational Therapy, School of Rehabilitation Science, Health Science University of Hokkaido, Hokkaido, Japan
| | - Sato Honma
- Research and Education Center for Brain Science, Hokkaido University, Hokkaido, Japan
| | - Ken-Ichi Honma
- Study Group for Monitoring of Brain Functions, Hokkaido University Graduate School of Medicine, Hokkaido, Japan.
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7
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Liu Q, Santamaria CM, Wei T, Zhao C, Ji T, Yang T, Shomorony A, Wang BY, Kohane DS. Hollow Silica Nanoparticles Penetrate the Peripheral Nerve and Enhance the Nerve Blockade from Tetrodotoxin. Nano Lett 2018; 18:32-37. [PMID: 29227106 DOI: 10.1021/acs.nanolett.7b02461] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The efficacy of tetrodotoxin (TTX), a very potent local anesthetic, is limited by its poor penetration through barriers to axonal surfaces. To address this issue, we encapsulated TTX in hollow silica nanoparticles (TTX-HSN) and injected them at the sciatic nerve in rats. TTX-HSN achieved an increased frequency of successful blocks, prolonged the duration of the block, and decreased the toxicity compared to free TTX. In animals injected with fluorescently labeled HSN, the imaging of frozen sections of nerve demonstrated that HSN could penetrate into nerve and that the penetrating ability of silica nanoparticles was highly size-dependent. These results demonstrated that HSN could deliver TTX into the nerve, enhancing efficacy while improving safety.
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Affiliation(s)
- Qian Liu
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Claudia M Santamaria
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Tuo Wei
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Chao Zhao
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Tianjiao Ji
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Tianshe Yang
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Andre Shomorony
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Bruce Y Wang
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Daniel S Kohane
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children's Hospital, Harvard Medical School , Boston, Massachusetts 02115, United States
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8
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Rwei AY, Wang B, Ji T, Zhan C, Kohane DS. Enhanced Triggering of Local Anesthetic Particles by Photosensitization and Photothermal Effect Using a Common Wavelength. Nano Lett 2017; 17:7138-7145. [PMID: 29058443 PMCID: PMC7491648 DOI: 10.1021/acs.nanolett.7b04176] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
On-demand pain relief systems would be very helpful additions to the armamentarium of pain management. Near-infrared triggered drug delivery systems have demonstrated the potential to provide such care. However, challenges remain in making such systems as stimulus-sensitive as possible, to enhance depth of tissue penetration, repeatability of triggering, and safety. Here we developed liposomes containing the local anesthetic tetrodotoxin and also containing a photosensitizer and gold nanorods that were excitable at the same near-infrared wavelength. The combination of triggering mechanisms enhanced the photosensitivity and repeatability of the system in vitro when compared with liposomes with a single photoresponsive component. In vivo, on-demand local anesthesia could be induced with a low irradiance and short irradiation duration, and liposomes containing both photosensitizer and gold nanorods were more effective than those containing just one photoresponsive component. Tissue reaction was benign.
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Affiliation(s)
- Alina Y. Rwei
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Bruce Wang
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Tianjiao Ji
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Changyou Zhan
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Daniel S. Kohane
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
- To whom correspondence may be addressed. (D.S. Kohane)
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Abstract
N-Methyl-D-aspartate (NMDA) receptor activation selectively releases the polyamines spermine and spermidine from the rat striatum in vivo. The intrastriatal injection of spermine or spermidine is neurotoxic, but this toxicity is not blocked by MK-801 and unlikely to be mediated via the NMDA receptor. The neurotoxic effects of intrastriatally injected NMDA can, however, be reduced by polyamine synthesis inhibition with difluoromethylornithine. Alterations in polyamine metabolism in the ischaemic brain, although perhaps induced by NMDA receptor activation, may contribute to ischaemic cell loss via NMDA-independent mechanisms, possibly related to the diverse effects of polyamines on calcium homoeostasis and channel function.
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Affiliation(s)
- A Porcella
- Department of Biology, Synthelabo Recherche (LERS), Bagneux, France
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10
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Covey DP, Bunner KD, Schuweiler DR, Cheer JF, Garris PA. Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids. Eur J Neurosci 2016; 43:1661-73. [PMID: 27038339 PMCID: PMC5819353 DOI: 10.1111/ejn.13248] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 03/29/2016] [Indexed: 02/04/2023]
Abstract
The reinforcing effects of abused drugs are mediated by their ability to elevate nucleus accumbens dopamine. Amphetamine (AMPH) was historically thought to increase dopamine by an action potential-independent, non-exocytotic type of release called efflux, involving reversal of dopamine transporter function and driven by vesicular dopamine depletion. Growing evidence suggests that AMPH also acts by an action potential-dependent mechanism. Indeed, fast-scan cyclic voltammetry demonstrates that AMPH activates dopamine transients, reward-related phasic signals generated by burst firing of dopamine neurons and dependent on intact vesicular dopamine. Not established for AMPH but indicating a shared mechanism, endocannabinoids facilitate this activation of dopamine transients by broad classes of abused drugs. Here, using fast-scan cyclic voltammetry coupled to pharmacological manipulations in awake rats, we investigated the action potential and endocannabinoid dependence of AMPH-induced elevations in nucleus accumbens dopamine. AMPH increased the frequency, amplitude and duration of transients, which were observed riding on top of slower dopamine increases. Surprisingly, silencing dopamine neuron firing abolished all AMPH-induced dopamine elevations, identifying an action potential-dependent origin. Blocking cannabinoid type 1 receptors prevented AMPH from increasing transient frequency, similar to reported effects on other abused drugs, but not from increasing transient duration and inhibiting dopamine uptake. Thus, AMPH elevates nucleus accumbens dopamine by eliciting transients via cannabinoid type 1 receptors and promoting the summation of temporally coincident transients, made more numerous, larger and wider by AMPH. Collectively, these findings are inconsistent with AMPH eliciting action potential-independent dopamine efflux and vesicular dopamine depletion, and support endocannabinoids facilitating phasic dopamine signalling as a common action in drug reinforcement.
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Affiliation(s)
- Dan P. Covey
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Kendra D. Bunner
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | - Douglas R. Schuweiler
- School of Biological Sciences, Illinois State University, 210 Julian Hall, Normal, IL 61790-4120, USA
| | - Joseph F. Cheer
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Paul A. Garris
- School of Biological Sciences, Illinois State University, 210 Julian Hall, Normal, IL 61790-4120, USA
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Abstract
We report a phototriggerable formulation enabling in vivo repeated and on-demand anesthesia with minimal toxicity. Gold nanorods (GNRs) that can convert near-infrared (NIR) light into heat were attached to liposomes (Lip-GNRs), enabling light-triggered phase transition of their lipid bilayers with a consequent release of payload. Lip-GNRs containing the site 1 sodium channel blocker tetrodotoxin and the α2-adrenergic agonist dexmedetomidine (Lip-GNR-TD) were injected subcutaneously in the rat footpad. Irradiation with an 808 nm continuous wave NIR laser produced on-demand and repeated infiltration anesthesia in the rat footpad in proportion to the irradiance, with minimal toxicity. The ability to achieve on-demand and repeated local anesthesia could be very beneficial in the management of pain.
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Affiliation(s)
- Changyou Zhan
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School , 300 Longwood Avenue, Boston, Massachusetts 02115, United States
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Weiping Wang
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School , 300 Longwood Avenue, Boston, Massachusetts 02115, United States
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - James B McAlvin
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School , 300 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - Shutao Guo
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School , 300 Longwood Avenue, Boston, Massachusetts 02115, United States
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Brian P Timko
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School , 300 Longwood Avenue, Boston, Massachusetts 02115, United States
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Claudia Santamaria
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School , 300 Longwood Avenue, Boston, Massachusetts 02115, United States
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Daniel S Kohane
- Laboratory for Biomaterials and Drug Delivery, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School , 300 Longwood Avenue, Boston, Massachusetts 02115, United States
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McGeoch AT, Wilkinson I, Fry AC. Poison arrows and pufferfish. QJM 2014; 107:663-5. [PMID: 24557732 DOI: 10.1093/qjmed/hcu041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- A T McGeoch
- From the Clinical Pharmacology Unit, Cambridge University Hospitals NHS Foundation Trust, Box 110, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK and Department of Acute Medicine, Cambridge University Hospitals NHS Foundation Trust, Box 273, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - I Wilkinson
- From the Clinical Pharmacology Unit, Cambridge University Hospitals NHS Foundation Trust, Box 110, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK and Department of Acute Medicine, Cambridge University Hospitals NHS Foundation Trust, Box 273, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - A C Fry
- From the Clinical Pharmacology Unit, Cambridge University Hospitals NHS Foundation Trust, Box 110, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK and Department of Acute Medicine, Cambridge University Hospitals NHS Foundation Trust, Box 273, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
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13
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Vornanen M, Hassinen M, Haverinen J. Tetrodotoxin sensitivity of the vertebrate cardiac Na+ current. Mar Drugs 2011; 9:2409-2422. [PMID: 22163193 PMCID: PMC3229242 DOI: 10.3390/md9112409] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 11/02/2011] [Accepted: 11/10/2011] [Indexed: 01/20/2023] Open
Abstract
Evolutionary origin and physiological significance of the tetrodotoxin (TTX) resistance of the vertebrate cardiac Na+ current (INa) is still unresolved. To this end, TTX sensitivity of the cardiac INa was examined in cardiac myocytes of a cyclostome (lamprey), three teleost fishes (crucian carp, burbot and rainbow trout), a clawed frog, a snake (viper) and a bird (quail). In lamprey, teleost fishes, frog and bird the cardiac INa was highly TTX-sensitive with EC50-values between 1.4 and 6.6 nmol·L−1. In the snake heart, about 80% of the INa was TTX-resistant with EC50 value of 0.65 μmol·L−1, the rest being TTX-sensitive (EC50 = 0.5 nmol·L−1). Although TTX-resistance of the cardiac INa appears to be limited to mammals and reptiles, the presence of TTX-resistant isoform of Na+ channel in the lamprey heart suggest an early evolutionary origin of the TTX-resistance, perhaps in the common ancestor of all vertebrates.
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Affiliation(s)
- Matti Vornanen
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +358-13-2513-383; Fax: +358-13-2513-590
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14
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Peng XQ, Gardner EL, Xi ZX. Gamma-vinyl GABA increases nonvesicular release of GABA and glutamate in the nucleus accumbens in rats via action on anion channels and GABA transporters. Psychopharmacology (Berl) 2010; 208:511-9. [PMID: 20033132 PMCID: PMC3713230 DOI: 10.1007/s00213-009-1753-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 12/01/2009] [Indexed: 02/06/2023]
Abstract
RATIONALE gamma-Amino butyric acid (GABA) is a well-characterized inhibitory neurotransmitter in the central nervous system, which may also stimulate nonvesicular release of other neurotransmitters under certain conditions. We have recently reported that gamma-vinyl GABA (GVG), an irreversible GABA transaminase inhibitor, elevates extracellular GABA but fails to alter dopamine release in the nucleus accumbens (NAc). OBJECTIVES Here, we investigated the mechanism(s) by which GVG elevates extracellular GABA levels and whether GVG also alters glutamate release in the NAc. MATERIALS AND METHODS In vivo microdialysis was used to simultaneously measure extracellular NAc GABA and glutamate before and after GVG administration in freely moving rats. RESULTS Systemic administration of GVG or intra-NAc local perfusion of GVG significantly increased extracellular NAc GABA and glutamate. GVG-enhanced GABA was completely blocked by intra-NAc local perfusion of 5-nitro-2, 3-(phenylpropylamino)-benzoic acid (NPPB), a selective anion channel blocker and partially blocked by SKF89976A, a type 1 GABA transporter inhibitor. GVG-enhanced glutamate was completely blocked by NPPB or SKF89976A. Tetrodotoxin, a voltage-dependent Na(+)-channel blocker, failed to alter GVG-enhanced GABA and glutamate. CONCLUSIONS These data suggest that GVG-enhanced extracellular GABA and glutamate are mediated predominantly by the opening of anion channels and partially by the reversal of GABA transporters. Enhanced extracellular glutamate may functionally attenuate the pharmacological action of GABA and prevent enhanced GABA-induced excess inhibition.
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Affiliation(s)
- Xiao-Qing Peng
- Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD 21224, USA
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15
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Wang CL, Guo C, Zhou Y, Wang R. In vitro and in vivo characterization of opioid activities of C-terminal esterified endomorphin-2 analogs. Peptides 2009; 30:1697-704. [PMID: 19520129 DOI: 10.1016/j.peptides.2009.06.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Revised: 06/01/2009] [Accepted: 06/02/2009] [Indexed: 11/22/2022]
Abstract
Previously, we have synthesized a series of endomorphin-2 (EM-2) analogs by the substitution of C-terminal amide group. In the present study, to further our knowledge of the influence of C-terminal esterified modification on the pharmacological activities, we investigated the in vitro and in vivo opioid activities of C-terminal esterified EM-2 analogs 1-3. Our results showed that the ED(50) values on contractions of the longitudinal muscle of distal colon induced by analogs 1-3 were about 1.5-fold higher, 2- and 8-fold lower than EM-2, respectively. In addition, intravenous (i.v.) injections of analogs 1 and 2 dose-dependently decreased the system arterial pressure (SAP) and heart rate (HR) in anesthetized rats, but the degree of the hypotension and bradycardia was significantly smaller relative to the parent. Moreover, analog 3 was almost ineffective. Nevertheless, all these analogs produced potent antinociception in the tail-flick test after intracerebroventricular (i.c.v.) injection, and this antinociception was inhibited by naloxone, indicating an opioid mechanism. In summary, these results gave the evidence that the conversion of C-terminal amide to esterified modification may play an important role in the regulation of opioid affinities and pharmacological activities.
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Affiliation(s)
- Chang-lin Wang
- State Key Laboratory of Chinese Medicine and Molecular Pharmacology, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
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16
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Abstract
Active neuronal transport along microtubules participates in the targeting of mRNAs, proteins and organelles to their sites of action. Cytoplasmic dynein represents a minus-end-directed microtubule-dependent motor protein. Due to the polarity of microtubules in axonal and distal dendritic compartments, with microtubule minus-ends pointing toward the inside of the cell, dyneins mainly mediate retrograde transport pathways in neurons. Since dyneins transport synaptic proteins, we asked whether changes in neuronal activity would in general influence dynein transport. KCl-induced depolarization, a condition that mimics the effects of neuronal activity, or pharmacological blockade of neuronal action potentials, respectively, was combined with neuronal live cell imaging, using an autofluorescent dynein intermediate chain fusion (monomeric red fluorescent protein [mRFP]-dynein intermediate chain [DIC]) as a model protein. Notably, we found that induced activity significantly reduced dynein particle mobility, as well as both the total distance and velocity of movements in mouse cultured hippocampal neurons. In contrast, blockade of neuronal action potentials through TTX did not alter any of the parameters analyzed. Neuronal depolarization processes therefore represent candidate mechanisms to regulate intracellular transport of neuronal cargoes.
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Affiliation(s)
- K Lardong
- Zentrum für Molekulare Neurobiologie Hamburg, ZMNH, Universität Hamburg, Falkenried 94, D-20251 Hamburg, Germany
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17
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Ikeda K, Murakami Y, Emoto Y, Ngy L, Taniyama S, Yagi M, Takatani T, Arakawa O. Transfer profile of intramuscularly administered tetrodotoxin to non-toxic cultured specimens of the pufferfish Takifugu rubripes. Toxicon 2008; 53:99-103. [PMID: 18996407 DOI: 10.1016/j.toxicon.2008.10.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 10/06/2008] [Accepted: 10/16/2008] [Indexed: 11/20/2022]
Abstract
Tetrodotoxin (TTX) was intramuscularly administered to non-toxic cultured specimens of the pufferfish Takifugu rubripes to investigate TTX transfer/accumulation profiles in the pufferfish body. In two groups of test fish administered either 50MU/individual of TTX standard (purified TTX; PTTX) or crude extract of toxic pufferfish ovary (crude TTX; CTTX), TTX rapidly transferred from the muscle via the blood to other organs. The toxin transfer profiles differed between groups, however, from 4 to 72h. In the PTTX group, little TTX was retained in the liver, and most (>96%) of the toxin remaining in the body transferred/accumulated in the skin after 12h, whereas in the CTTX group, a considerable amount of toxin (15%-23% of the administered toxin or 28%-58% of the remaining toxin) was transferred/retained in the liver for up to 24h, despite the fact that 89% of the remaining toxin transferred/accumulated in the skin at the end of rearing period (168h). The total amount of toxin remaining in the entire body at 1-4h was approximately 60% of the administered toxin in both groups, which decreased at 8-12h, and then increased again to approximately 60%-80% at 24-168h. Immunohistochemical observation revealed that the toxin accumulated in the skin was localized at the basal cells of the epidermal layer.
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Affiliation(s)
- Koichi Ikeda
- Graduate School of Science and Technology, Nagasaki University, Nagasaki 852-8521, Japan
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18
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Alguacil LF, Pérez-García C, Salas E, González-Martín C, Castillo C, Polanco MJ, Herradón G, Morales L. Subcutaneous tetrodotoxin and inflammatory pain. Br J Anaesth 2008; 100:729-30. [PMID: 18407950 DOI: 10.1093/bja/aen066] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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19
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Kitamura C, Takahashi M, Kondoh Y, Tashiro H, Tashiro T. Identification of synaptic activity-dependent genes by exposure of cultured cortical neurons to tetrodotoxin followed by its withdrawal. J Neurosci Res 2007; 85:2385-99. [PMID: 17551986 DOI: 10.1002/jnr.21391] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Activity-dependent gene expression is one of the key mechanisms of synaptic plasticity that form the basis of higher order functions such as learning and memory. In the present study, we surveyed for activity-dependent genes by analyzing gene expression changes accompanying reversible inhibition of synaptic activity by tetrodotoxin (TTX) using two types of DNA microarrays; our focused oligo DNA microarray "Synaptoarray" and the commercially available high-density array. Cerebral cortical cells from E18 rat embryos were cultured for 14 days to ensure synaptogenesis, then treated with 1 muM TTX for 48 hr without detectable effect on cell viability. Synaptic density estimated by the amount of Synapsin I and Synaptotagmin I was decreased 21-24% by TTX treatment, but recovered to the control level 48 hr after TTX withdrawal. Comparison of gene expression profiles by competitive hybridization of fluorescently labeled cRNA from TTX-treated and control cells showed an overall downregulation of the genes on the Synaptoarray by TTX-treatment with different recovery rates after TTX withdrawal. With 16 representative genes, microarray data were validated by real-time PCR analysis. Genes most severely downregulated by TTX and upregulated above the control level at 5 hr after TTX withdrawal were munc13-1 (involved in docking and priming of synaptic vesicles) and Shank2 (involved in the postsynaptic scaffold). In addition, comprehensive screening at 5 hr after TTX withdrawal using high density arrays resulted in additional identification of Rgs2, a regulator of trimeric G-protein signaling, as an activity-dependent gene. These three genes are thus likely to be key factors in the regulation of synaptic plasticity. (c) 2007 Wiley-Liss, Inc.
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Affiliation(s)
- Chikara Kitamura
- Department of Chemistry and Biological Science, School of Science and Engineering, Aoyama-Gakuin University, Sagamihara, Kanagawa, Japan
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20
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Mojumder DK, Frishman LJ, Otteson DC, Sherry DM. Voltage-gated sodium channel alpha-subunits Na(v)1.1, Na(v)1.2, and Na(v)1.6 in the distal mammalian retina. Mol Vis 2007; 13:2163-2182. [PMID: 18079688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Accepted: 10/29/2007] [Indexed: 05/25/2023] Open
Abstract
PURPOSE Recent studies indicate the presence of functional voltage-gated sodium channels (Na(v) channels) in the distal retina in several species. This study examined the distribution of Na(v) channels in the outer plexiform layer (OPL) of rat, mouse, and rabbit retinas. METHODS Immunohistochemical and electroretinographic approaches were used. RESULTS Antibodies specific for Na(v)1 alpha-subunits appropriately labeled retinal ganglion cells, their axons, and amacrine cells that are known to have tetrodotoxin (TTX)-sensitive Na(v) channels. Pan-Na(v), Na(v)1.2, and Na(v)1.6 labeling was found in horizontal cells and processes in all three species. Weaker Na(v)1.1 labeling was observed in rodent horizontal cells, but some rabbit horizontal cells and processes were prominently labeled. Additional labeling for Na(v)1.1, Na(v)1.2, and Na(v)1.6 that was not attributable to horizontal cells was also present in the OPL. Much of this labeling was diffusely distributed. Some of the additional Na(v)1.1 labeling was associated with photoreceptor terminals. By exclusion using photoreceptor and horizontal cell markers, some of this labeling could have been associated with bipolar cell dendrites, although colocalization was not directly established due to the diffuse nature of the labeling and limits on anatomical resolution. No Na(v)1 alpha-subunit labeling was observed in bipolar cell bodies. Testing for functional Na(v) channels was performed by recording full field flash electroretinograms from dark-adapted rats before and after intravitreal injections of TTX, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), or TTX+CNQX. TTX and CNQX+TTX, but not CNQX alone, greatly attenuated the dark-adapted cone-driven b-waves. CONCLUSIONS Horizontal cells from three different mammalian retinas showed prominent labeling for Na(v)1 alpha-subunits. Some additional diffuse Na(v)1 alpha-subunit labeling in the OPL was associated with photoreceptor terminals. Na(v)1 alpha-subunit labeling also may have been present on bipolar cell dendrites, although it was not possible to establish this localization unequivocally by immunostaining. However, cone-driven b-waves in rats were reduced in maximum amplitude by TTX in the presence of CNQX which blocks synaptic input to horizontal, amacrine, and ganglion cells. This finding is consistent with TTX effects on the b-wave being due to blockade of Na(v) channels in cone bipolar cell dendrites in the OPL. The role of Na(v) channels in horizontal cells remains to be determined.
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Affiliation(s)
- Deb K Mojumder
- University of Houston College of Optometry, Houston, TX, USA
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21
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Lang PM, Hilmer VB, Grafe P. Differential Contribution of Sodium Channel Subtypes to Action Potential Generation in Unmyelinated Human C-type Nerve Fibers. Anesthesiology 2007; 107:495-501. [PMID: 17721253 DOI: 10.1097/01.anes.0000278862.77981.c8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Background
Multiple voltage-dependent sodium channels (Na(v)) contribute to action potentials and excitability of primary nociceptive neurons. The aim of the current study was to characterize subtypes of Na(v) that contribute to action potential generation in peripheral unmyelinated human C-type nerve fibers.
Methods
Registration of C-fiber compound action potentials and determination of membrane threshold was performed by a computerized threshold tracking program. Nerve fibers were stimulated with a 1-ms current pulse either alone or after a small ramp current lasting 300 ms.
Results
Compound C-fiber action potentials elicited by supramaximal 1-ms current pulses were rather resistant to application of tetrodotoxin (30-90 nM). However, the same concentrations of tetrodotoxin strongly reduced the peak height and elevated membrane threshold of action potentials evoked at the end of a 300-ms current ramp. A similar effect was observed during application of lidocaine and mexiletine (50 microM each).
Conclusions
These data indicate that more than one type of Na(v) contributes to the generation of action potentials in unmyelinated human C-type nerve fibers. The peak height of an action potential produced by a short electrical impulse is dependent on the activation of tetrodotoxin-resistant ion channels. In contrast, membrane threshold and action potential peak height at the end of a slow membrane depolarization are regulated by a subtype of Na(v) with high sensitivity to low concentrations of tetrodotoxin, lidocaine, and mexiletine. The electrophysiologic and pharmacologic characteristics may indicate the functional activity of the Na(v) 1.7 subtype of voltage-dependent sodium channels.
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Affiliation(s)
- Philip M Lang
- Department of Anesthesiology, University of Munich, Munich, Germany.
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22
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Hagen NA, Fisher KM, Lapointe B, du Souich P, Chary S, Moulin D, Sellers E, Ngoc AH. An open-label, multi-dose efficacy and safety study of intramuscular tetrodotoxin in patients with severe cancer-related pain. J Pain Symptom Manage 2007; 34:171-82. [PMID: 17662911 DOI: 10.1016/j.jpainsymman.2006.11.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 11/01/2006] [Accepted: 11/04/2006] [Indexed: 11/17/2022]
Abstract
Cancer pain is a prevalent and serious public health issue, and more effective treatments are needed. This study evaluates the analgesic activity of tetrodotoxin, a highly selective sodium channel blocker, in cancer pain. A Phase IIa, open-label, multicenter, dose-escalation study of intramuscular tetrodotoxin was conducted in patients with severe, unrelieved cancer pain. The study design called for six ascending dose levels of intramuscular tetrodotoxin, administered over a four-day treatment period in hospitalized patients, with six patients to be enrolled within each successive dose level. Twenty-four patients underwent 31 courses of treatment at doses ranging from 15 to 90 microg daily, administered in divided doses, over four days. Most patients described transient perioral tingling or other mild sensory phenomena within about an hour of each treatment. Nausea and other toxicities were generally mild, but two patients experienced a serious adverse event, truncal and gait ataxia, that resolved over days. Seventeen of 31 treatments resulted in clinically meaningful reductions in pain intensity, and relief of pain persisted for up to two weeks or longer. Two patients had opioids held due to narcosis concurrent with relief of pain. Somatic, visceral, or neuropathic pain could all respond, but it was not possible to predict which patients were more likely to have an analgesic effect. Tetrodotoxin was overall safe. It effectively relieved severe, treatment-resistant cancer pain in the majority of patients and often for prolonged periods after treatment. It may have a novel mechanism of analgesic effect. Further study is warranted.
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Affiliation(s)
- Neil A Hagen
- Tom Baker Cancer Centre, Calgary, Alberta, Canada.
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23
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Abstract
BACKGROUND Chronic pain conditions may result from peripheral nerve injury, chronic peripheral inflammation, or sensory ganglia inflammation. However, inflammatory processes may also contribute to peripheral nerve injury responses. To isolate the contribution of local inflammation of sensory ganglia to chronic pain states, the authors previously developed a rat model in which long-lasting pain is induced by inflaming sensory ganglia without injuring the neurons. This results in prolonged mechanical pain, local increases in proinflammatory cytokines, increased neuronal hyperexcitability, and abnormal spontaneous activity. METHODS The authors used whole cell patch clamp in acutely isolated small-diameter neurons to determine how localized inflammation (3-5 days) of L4 and L5 ganglia altered voltage-gated K and Na currents. RESULTS Tetrodotoxin-sensitive Na currents increased twofold to threefold in neurons from inflamed ganglia. Tetrodotoxin-resistant Na currents increased more than twofold, but only in cells that bound isolectin B4. These increases occurred without shifts in voltage dependence of activation and inactivation. Similar results are seen in models of peripheral inflammation, except for the large magnitudes. Unlike most pain models, localized inflammation increased rather than decreased voltage-gated K currents, due to increased amplitudes of the sustained (delayed rectifier) and fast-inactivating transient components. The overall effect in current clamp experiments was an increase in excitability as indicated by decreased rheobase and lower action potential threshold. CONCLUSIONS Neuronal inflammation per se, in the absence of nerve injury, causes large increases in Na channel density and enhanced excitability. The unusual finding of increased K current may reflect regulation of excitability in the face of such large increases in Na current.
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MESH Headings
- Action Potentials/drug effects
- Anesthetics, Local/administration & dosage
- Animals
- Cells, Cultured
- Disease Models, Animal
- Electric Conductivity
- Electrophysiology/methods
- Female
- Ganglia, Spinal/cytology
- Ganglia, Spinal/physiopathology
- Inflammation/physiopathology
- Ion Channel Gating
- Membrane Potentials/drug effects
- Neural Conduction/drug effects
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Patch-Clamp Techniques/methods
- Potassium Channels, Voltage-Gated/drug effects
- Potassium Channels, Voltage-Gated/metabolism
- Rats
- Rats, Sprague-Dawley
- Sodium Channels/drug effects
- Sodium Channels/metabolism
- Tetrodotoxin/administration & dosage
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Affiliation(s)
- Jun-Gang Wang
- Research Fellow, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA
| | - Judith A. Strong
- Research Associate Professor, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA
| | - Wenrui Xie
- Research Fellow, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA
| | - Jun-Ming Zhang
- Associate Professor and Director of Research, Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA
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24
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van Duuren E, van der Plasse G, van der Blom R, Joosten RNJMA, Mulder AB, Pennartz CMA, Feenstra MGP. Pharmacological Manipulation of Neuronal Ensemble Activity by Reverse Microdialysis in Freely Moving Rats: A Comparative Study of the Effects of Tetrodotoxin, Lidocaine, and Muscimol. J Pharmacol Exp Ther 2007; 323:61-9. [PMID: 17626795 DOI: 10.1124/jpet.107.124784] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To be able to address the question how neurotransmitters or pharmacological agents influence activity of neuronal populations in freely moving animals, the combidrive was developed. The combidrive combines an array of 12 tetrodes to perform ensemble recordings with a moveable and replaceable microdialysis probe to locally administer pharmacological agents. In this study, the effects of cumulative concentrations of tetrodotoxin, lidocaine, and muscimol on neuronal firing activity in the prefrontal cortex were examined and compared. These drugs are widely used in behavioral studies to transiently inactivate brain areas, but little is known about their effects on ensemble activity and the possible differences between them. The results show that the combidrive allows ensemble recordings simultaneously with reverse microdialysis in freely moving rats for periods at least up to 2 wk. All drugs reduced neuronal firing in a concentration dependent manner, but they differed in the extent to which firing activity of the population was decreased and the in speed and extent of recovery. At the highest concentration used, both muscimol and tetrodotoxin (TTX) caused an almost complete reduction of firing activity. Lidocaine showed the fastest recovery, but it resulted in a smaller reduction of firing activity of the population. From these results, it can be concluded that whenever during a behavioral experiment a longer lasting, reversible inactivation is required, muscimol is the drug of choice, because it inactivates neurons to a similar degree as TTX, but it does not, in contrast to TTX, affect fibers of passage. For a short-lasting but partial inactivation, lidocaine would be most suitable.
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Affiliation(s)
- E van Duuren
- Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, 1105BA Amsterdam, The Netherlands
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25
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Dong XW, Goregoaker S, Engler H, Zhou X, Mark L, Crona J, Terry R, Hunter J, Priestley T. Small interfering RNA-mediated selective knockdown of NaV1.8 tetrodotoxin-resistant sodium channel reverses mechanical allodynia in neuropathic rats. Neuroscience 2007; 146:812-21. [PMID: 17367951 DOI: 10.1016/j.neuroscience.2007.01.054] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 01/23/2007] [Accepted: 01/26/2007] [Indexed: 01/10/2023]
Abstract
The biophysical properties of a tetrodotoxin resistant (TTXr) sodium channel, Na(V)1.8, and its restricted expression to the peripheral sensory neurons suggest that blocking this channel might have therapeutic potential in various pain states and may offer improved tolerability compared with existing sodium channel blockers. However, the role of Na(V)1.8 in nociception cannot be tested using a traditional pharmacological approach with small molecules because currently available sodium channel blockers do not distinguish between sodium channel subtypes. We sought to determine whether small interfering RNAs (siRNAs) might be capable of achieving the desired selectivity. Using Northern blot analysis and membrane potential measurement, several siRNAs were identified that were capable of a highly-selective attenuation of Na(V)1.8 message as well as functional expression in clonal ND7/23 cells which were stably transfected with the rat Na(V)1.8 gene. Functional knockdown of the channel was confirmed using whole-cell voltage-clamp electrophysiology. One of the siRNA probes showing a robust knockdown of Na(V)1.8 current was evaluated for in vivo efficacy in reversing an established tactile allodynia in the rat chronic constriction nerve-injury (CCI) model. The siRNA, which was delivered to lumbar dorsal root ganglia (DRG) via an indwelling epidural cannula, caused a significant reduction of Na(V)1.8 mRNA expression in lumbar 4 and 5 (L4-L5) DRG neurons and consequently reversed mechanical allodynia in CCI rats. We conclude that silencing of Na(V)1.8 channel using a siRNA approach is capable of producing pain relief in the CCI model and further support a role for Na(V)1.8 in pathological sensory dysfunction.
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Affiliation(s)
- X-W Dong
- Department of Neurobiology, Schering-Plough Research Institute, K-15-2-2600, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA.
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26
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Abstract
Conventional local anesthetics such as bupivacaine cause considerable myotoxicity and neurotoxicity, whereas tetrodotoxin (TTX) does not. Tetrodotoxin combined with bupivacaine or vasoconstrictors produces long-duration nerve blockade. To assess whether these prolonged blocks can be produced without increased myotoxicity, Sprague-Dawley rats were injected with bupivacaine, TTX, and both, or TTX plus epinephrine. Median durations of thermal nociceptive blockade were, respectively, 188, 401, 882, and 972 min. On dissection 4 days later, all tissues appeared macroscopically pristine. Muscle injury was at most mild to moderate in all animals, and the muscle injury scores for the combination formulations were not higher than for bupivacaine alone. Similarly, in differentiated cells from a myoblast cell line (C2C12), TTX caused either no or minimal worsening of cell viability from bupivacaine at 2 or 7 days. Epinephrine did not worsen TTX's relatively minimal cytotoxicity. Tetrodotoxin may thus be useful in producing prolonged nerve block with minimal myotoxicity and perhaps neurotoxicity.
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Affiliation(s)
- Robert F Padera
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, USA
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Saxon DW, White G. Episodic vestibular disruption following ablation of the inferior olive in rats: Behavioral correlates. Behav Brain Res 2006; 175:128-38. [PMID: 16979764 DOI: 10.1016/j.bbr.2006.08.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Revised: 08/11/2006] [Accepted: 08/12/2006] [Indexed: 01/03/2023]
Abstract
The experiments herein investigate whether the behavioral responses to transient and episodic vestibular disruption and permanent ablation are distinct in the absence of climbing fiber input. Subjects in group 1 received an IP injection of PBS followed by an IP injection of niacinamide. Seven days later these rats received the first of 3 serial transtympanic injections of TTX on the same side with 7 days between each injection. Following each TTX injection rats displayed unilateral vestibular symptoms that persisted beyond 48h. Spontaneous barrel rolling behavior was not observed. Group 2 subjects received an IP injection of 3-acetylpyridine (3-AP)+niacinamide followed by the same TTX regimen as group 1. Following each TTX injection vestibular symptoms (severe body twisting and persistent spontaneous barrel rolling) emerged rapidly (<15min) and resolved by 72h. Group 3 subjects received an IP injection of 3-AP+niacinamide and 7 days later a single unilateral transtympanic injection of sodium arsanilate. Rats in group 3 developed vestibular symptoms similar to those observed in group 2 although there was no resolution of these symptoms. The results indicate that TTX has a rapid rate of infiltration and blockade of the VIIIth nerve that persists for >48h and then completely resolves. The contrast in vestibular symptoms between groups 1 and 2 suggest that climbing fibers are recruited soon after onset of vestibular disruption and play a role in attenuating the severity of vestibular symptoms associated with transient/episodic vestibular disruption.
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Affiliation(s)
- Dale W Saxon
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Evansville Center for Medical Education, 8600 University Blvd., Evansville, IN 47712, United States.
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Prado-Alcalá RA, Díaz del Guante MA, Garín-Aguilar ME, Díaz-Trujillo A, Quirarte GL, McGaugh JL. Amygdala or hippocampus inactivation after retrieval induces temporary memory deficit☆. Neurobiol Learn Mem 2006; 86:144-9. [PMID: 16540353 DOI: 10.1016/j.nlm.2006.01.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Revised: 01/05/2006] [Accepted: 01/26/2006] [Indexed: 12/01/2022]
Abstract
The hypothesis that memory is stored through a single stage of consolidation that results in a stable and lasting long-term memory has been challenged by the proposition that reactivation of a memory induces reconsolidation of the memory. The reconsolidation hypothesis is supported by evidence that, under some conditions, post-retrieval treatments affecting amygdala and hippocampus functioning impair subsequent retention performance. We now report that repeated retention testing attenuates the performance impairment induced by post-retrieval reversible inactivation of the amygdala and hippocampus of rats induced by tetrodotoxin. These findings challenge the reconsolidation hypothesis and suggest that the post-retrieval retention performance impairment is best explained as due to temporary retrieval failure.
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Miyamoto H, Tazawa Y, Hayasaka A, Nitta J, Egawa I, Kurosaka D. The s-Wave of the Multifocal Electroretinogram in Cats. Jpn J Ophthalmol 2006; 50:432-437. [PMID: 17013695 DOI: 10.1007/s10384-006-0345-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 05/11/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE To characterize the s-wave of the multifocal electroretinogram (mfERG) in cats, and to determine the contribution of the inner retina to the s-wave by examining the effects of tetrodotoxin (TTX) and N-methyl D: -aspartate (NMDA) injected into the vitreous cavity. METHODS mfERGs were recorded from 15 eyes of 15 male cats under general anesthesia. The stimulus consisted of 37 elements, and the luminance of the bright and the black elements were 200 and 4 cd/m2, respectively. The stimuli were presented in a pseudorandom binary m-sequence at six different base periods (bpds) from 13.3 to 426.7 ms. Fifty microliters of 7.0 microM TTX followed by 50 microl of 4.0 mM NMDA were injected into the vitreous cavity. RESULTS The shape of the mfERGs in the cats resembled that in humans. The s-wave appeared on the descending limb of P1, as seen in human mfERGs, in 11 eyes, and the s-wave amplitude increased significantly as the bpd was increased. TTX and NMDA resulted in the disappearance of the s-wave at all bpds, while the amplitude of P1 remained unchanged. CONCLUSIONS The s-wave is present in the mfERG in the cat, and its loss following injections of TTX and NMDA supports the view that the s-wave reflects the function of the ganglion cells and their axons.
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Affiliation(s)
- Hiroyuki Miyamoto
- Department of Ophthalmology, Iwate Medical University School of Medicine, Morioka, Japan
| | - Yutaka Tazawa
- Department of Ophthalmology, Iwate Medical University School of Medicine, Morioka, Japan.
| | - Akira Hayasaka
- Department of Ophthalmology, Iwate Medical University School of Medicine, Morioka, Japan
| | - Junfuku Nitta
- Department of Ophthalmology, Iwate Medical University School of Medicine, Morioka, Japan
| | - Isao Egawa
- Department of Ophthalmology, Iwate Medical University School of Medicine, Morioka, Japan
| | - Daijiro Kurosaka
- Department of Ophthalmology, Iwate Medical University School of Medicine, Morioka, Japan
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Lopez-Santiago LF, Pertin M, Morisod X, Chen C, Hong S, Wiley J, Decosterd I, Isom LL. Sodium channel beta2 subunits regulate tetrodotoxin-sensitive sodium channels in small dorsal root ganglion neurons and modulate the response to pain. J Neurosci 2006; 26:7984-94. [PMID: 16870743 PMCID: PMC6674206 DOI: 10.1523/jneurosci.2211-06.2006] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Voltage-gated sodium channel (Na(v)1) beta2 subunits modulate channel gating, assembly, and cell-surface expression in CNS neurons in vitro and in vivo. beta2 expression increases in sensory neurons after nerve injury, and development of mechanical allodynia in the spared nerve injury model is attenuated in beta2-null mice. Thus, we hypothesized that beta2 modulates electrical excitability in dorsal root ganglion (DRG) neurons in vivo. We compared sodium currents (I(Na)) in small DRG neurons from beta2+/+ and beta2-/- mice to determine the effects of beta2 on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na(v)1 in vivo. Small-fast DRG neurons acutely isolated from beta2-/- mice showed significant decreases in TTX-S I(Na) compared with beta2+/+ neurons. This decrease included a 51% reduction in maximal sodium conductance with no detectable changes in the voltage dependence of activation or inactivation. TTX-S, but not TTX-R, I(Na) activation and inactivation kinetics in these cells were slower in beta2(-/-) mice compared with controls. The selective regulation of TTX-S I(Na) was supported by reductions in transcript and protein levels of TTX-S Na(v)1s, particularly Na(v)1.7. Low-threshold mechanical sensitivity was preserved in beta2-/- mice, but they were more sensitive to noxious thermal stimuli than wild type whereas their response during the late phase of the formalin test was attenuated. Our results suggest that beta2 modulates TTX-S Na(v)1 mRNA and protein expression resulting in increased TTX-S I(Na) and increases the rates of TTX-S Na(v)1 activation and inactivation in small-fast DRG neurons in vivo. TTX-R I(Na) were not significantly modulated by beta2.
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Beloeil H, Ababneh Z, Chung R, Zurakowski D, Mulkern RV, Berde CB. Effects of bupivacaine and tetrodotoxin on carrageenan-induced hind paw inflammation in rats (Part 1): hyperalgesia, edema, and systemic cytokines. Anesthesiology 2006; 105:128-38. [PMID: 16810004 DOI: 10.1097/00000542-200607000-00022] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Local anesthetics exert antiinflammatory actions. To elucidate potential mechanisms, the authors examined effects of bupivacaine or tetrodotoxin, administered to rats by ipsilateral or contralateral sciatic blockade or systemically, on carrageenan-induced hind paw hyperalgesia, edema, and stimulated cytokine production in circulating blood cells. METHODS Twelve groups of rats (n = 9-12) received injections in three sites: (1) right or left hind paw (carrageenan or saline), (2) left sciatic block, and (3) systemically (subcutaneously in the upper back). Sciatic and systemic injections were performed with epinephrine plus bupivacaine, tetrodotoxin, or saline; injections were repeated 6 h later. Fifteen hours later, hyperalgesia and/or sensory and motor block were assessed behaviorally, and paw edema was quantified by magnetic resonance imaging. Stimulated production of tumor necrosis factor alpha, interleukin 10, and interleukin 1beta in whole blood cultures was measured by enzyme-linked immunosorbent assay. RESULTS Either ipsilateral or contralateral sciatic blocks using either bupivacaine or tetrodotoxin reduced carrageenan-induced edema and hyperalgesia. Systemic bupivacaine and tetrodotoxin were ineffective in preventing edema and hyperalgesia. Bupivacaine was effective in suppressing systemic tumor necrosis factor alpha and interleukin 1beta by all three routes, whereas tetrodotoxin was ineffective by all three routes. CONCLUSION Bupivacaine and tetrodotoxin, via a contralateral or ipsilateral sciatic block, attenuate local inflammatory edema and hyperalgesia induced by hind paw injection of carrageenan in rats. Mechanisms underlying contralateral effects of sciatic blockade remain unexplained. Bupivacaine inhibits carrageenan-evoked systemic cytokine production by a mechanism not shared by tetrodotoxin; this action may involve tetrodotoxin-resistant sodium channels or a variety of non-sodium-channel targets.
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Affiliation(s)
- Hélène Beloeil
- Department of Anesthesiology, Perioperative and Pain Medicine, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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Fuchs RA, Feltenstein MW, See RE. The role of the basolateral amygdala in stimulus-reward memory and extinction memory consolidation and in subsequent conditioned cued reinstatement of cocaine seeking. Eur J Neurosci 2006; 23:2809-13. [PMID: 16817884 DOI: 10.1111/j.1460-9568.2006.04806.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The consolidation of cue-cocaine associations and extinction learning (i.e. cue-no cocaine associations) into long-term memory probably regulates the long-lasting control of conditioned stimuli (CS) over cocaine-seeking behaviour, and the basolateral amygdala (BLA) may play a role in this phenomenon. To test this hypothesis, rats previously trained to self-administer cocaine underwent a single classical conditioning (CC) session, during which they received passive pairings of cocaine infusions and a novel light + tone stimulus complex. After additional self-administration sessions in the absence of CS presentation and subsequent extinction training sessions, the ability of the CS to reinstate cocaine-seeking on five test days was assessed. Rats received intra-BLA microinfusions of vehicle or the Na+-channel blocker tetrodotoxin (TTX) immediately after CC (consolidation of CS-cocaine associations) or immediately after reinstatement testing (consolidation of extinction learning). TTX administered immediately after CC attenuated subsequent CS-induced reinstatement. In contrast, TTX administered after the first reinstatement test impaired the extinction of cocaine-seeking behaviour during a second reinstatement test by disrupting extinction memory. Overall, these findings suggest that Na+ channel-mediated mechanisms within the BLA mediate the consolidation of both cocaine-stimulus association and extinction learning, two processes that have opposite effects on subsequent cue-induced cocaine-seeking behaviour.
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Affiliation(s)
- Rita A Fuchs
- Department of Psychology, University of North Carolina at Chapel Hill, 27599, USA
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Abstract
Background
The authors previously showed that bupivacaine and tetrodotoxin via contralateral or ipsilateral sciatic block, but not systemically, attenuate local edema and hyperalgesia induced by carrageenan hind paw injection in rats. Bupivacaine, by all three routes, suppressed systemic cytokine activation, whereas tetrodotoxin was ineffective by all three routes. In the current study, the authors examined cytokine and p38 mitogen-activated protein kinase (MAPK) activation in lumbar dorsal root ganglia (DRGs) and spinal cord after carrageenan paw injections and sciatic blocks with either bupivacaine or tetrodotoxin.
Methods
Ten groups of rats (n = 3-5) received injections in the following sites: right or left hind paw or right forepaw (carrageenan or saline) and left sciatic block (with epinephrine plus bupivacaine, tetrodotoxin, or saline; repeated 6 h later). Fifteen hours later, tumor necrosis factor alpha, interleukin 1beta, p38 MAPK, and phosphorylated p38 MAPK were measured by enzyme-linked immunosorbent assay in DRGs and in the spinal cord.
Results
Carrageenan-induced hind paw inflammation enhanced tumor necrosis factor-alpha and interleukin-1beta production in bilateral DRGs and spinal cord and enhanced p38 MAPK activation in bilateral DRGs. These pathways were not activated after forepaw injection of carrageenan, suggesting a segmental mechanism. Neither bupivacaine nor tetrodotoxin inhibited cytokine and p38 MAPK activation after carrageenan injection.
Conclusion
Ipsilateral or contralateral sciatic blockade using either bupivacaine or tetrodotoxin does not inhibit carrageenan-induced activation of cytokines and p-38 MAPK in spinal cord and DRGs. Possible explanations may include incomplete degrees of conduction blockade or afferent signaling via saphenous nerves.
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Affiliation(s)
- Hélène Beloeil
- Department of Anesthesiology, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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Takeno K, Shimogori H, Takemoto T, Tanaka K, Mikuriya T, Orita H, Yamashita H. The systemic application of diazepam facilitates the reacquisition of a well-balanced vestibular function in a unilateral vestibular re-input model with intracochlear tetrodotoxin infusion using an osmotic pump. Brain Res 2006; 1096:113-9. [PMID: 16756965 DOI: 10.1016/j.brainres.2006.04.030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Revised: 04/07/2006] [Accepted: 04/10/2006] [Indexed: 11/18/2022]
Abstract
Diazepam is a popular medicine used in the treatment of acute vertigo. In the past, many studies investigating the effect of diazepam in peripheral vestibular destruction have been reported. However, no previous study has yet investigated the effect of diazepam on a model with a transient and reversible vestibular function similar to recurrent vertigo as seen in Meniere's disease. We thus made a peripheral vestibular re-input model by the unilateral intracochlear administration of tetrodotoxin (TTX) using an osmotic pump and then examined the influence of diazepam on the vestibular system in this model. Hartley white guinea pigs were intracochlearly administered with TTX on the right side for 3 days by an osmotic pump. Animals were divided into three groups, TTX alone (control group (n = 7)), TTX and an intraperitoneal diazepam injection once a day for 3 days (diazepam group (n = 6)) and vehicle injection (vehicle group (n = 6)). A caloric response and vestibuloocular reflex (VOR) were observed at 7 and 14 days after completing 3 days of TTX administration. Seven days after vestibular re-input, a directional preponderance of the nystagmus (DP) to the TTX-treated side was observed in the control and vehicle groups on VOR examination. DP was not observed in the diazepam group on any examined day. The R/L time ratio of caloric response showed no statistical difference between three groups on any examined day. These results suggest that diazepam may thus be useful for patients in an acute stage of peripheral vestibular vertigo by decreasing their vertiginous symptoms.
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Affiliation(s)
- Kenji Takeno
- Department of Otolaryngology, Yamaguchi University School of Medicine, Ube, Japan
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Abstract
BACKGROUND Tetrodotoxin (TTX) is a powerful sodium channel blocker extracted from the puffer fish. The analgesic effects of TTX were investigated in different animal pain models. METHODS Wistar rats were submitted to the formalin test and to partial ligation of the sciatic nerve (Seltzer's model). Swiss Webster mice were used in the writhing test. Rodents were divided into six groups receiving a s.c. injection of either 0.9% NaCl, TTX 0.3, 1, 3, or 6 microg kg(-1), or morphine (5 mg kg(-1)). Substances were injected 30 min before 2.5% formalin injection into the hind paw, acetic acid administration intraperitoneally or neuropathic pain testing consisting of mechanical allodynia (von Frey filament) and thermal hyperalgesia (Plantar test). RESULTS TTX decreased pain behaviour in the formalin test at the highest dose and in the writhing test at 3 and 6 microg kg(-1). It also diminished mechanical allodynia and thermal hyperalgesia with an ED(50) of 1.08 (0.89) and 0.62 (0.33) microg kg(-1), respectively. Observation of the rats after TTX injection did not show any motor deficit, respiratory distress or sedation. Morphine was also effective in relieving pain in all three tests but with signs of considerable sedation. CONCLUSION Systemic injections of TTX diminished pain behaviour in a dose-dependent manner in models of inflammatory, visceral and neuropathic pain without causing adverse events, whereas morphine analgesia was associated with heavy sedation. TTX is a very promising substance for the treatment of various types of pain but needs further evaluation.
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Affiliation(s)
- J Marcil
- Department of Anesthesiology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada
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Nishijima T, Soya H. Evidence of functional hyperemia in the rat hippocampus during mild treadmill running. Neurosci Res 2006; 54:186-91. [PMID: 16364480 DOI: 10.1016/j.neures.2005.11.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Revised: 11/01/2005] [Accepted: 11/14/2005] [Indexed: 11/29/2022]
Abstract
Exercise appears to improve hippocampal plasticity and cognitive function, leading us to postulate that exercise may activate hippocampal neurons, which in turn increase hippocampal cerebral blood flow (Hip-CBF). Recent studies using laser-Doppler flowmetry (LDF) have shown that Hip-CBF increases with behavior and locomotion, but it has not been examined whether these changes are due to neuronal activation. We aimed to examine whether functional hyperemia, an increase in cerebral blood flow in response to neuronal activation, can occur in the exercising rat hippocampus. We applied a treadmill running model of rats and LDF combined with microdialysis. Prolonged mild treadmill running (10 m/min) resulted in an increase in Hip-CBF of 26+/-9% versus basal level. When tetrodotoxin was infused via microdialysis into the loci where Hip-CBF was monitored, the increased Hip-CBF with running was completely suppressed. These results provide evidence that functional hyperemia occurs in the rat hippocampus during mild treadmill running and suggest that our running animal model may be useful for examining the underlying mechanisms of exercise-induced hippocampal functional hyperemia.
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Affiliation(s)
- Takeshi Nishijima
- Laboratory of Exercise Biochemistry, University of Tsukuba Graduate School of Comprehensive Human Sciences, Tsukuba 305-8574, Ibaraki, Japan
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Abstract
PURPOSE To investigate the contribution to the photopic negative response (PhNR) of the electroretinogram (ERG) by retinal ganglion cells (RGCs). The PhNR was assessed longitudinally following optic nerve transection (ONTx). METHODS Photopic ERGs were recorded from each eye of an anesthetized (ketamine/xylazine, 60 mg/kg and 5 mg/kg) Brown Norway rat using custom made electrodes (PT-IR Tef., A-M System Inc). ERGs were elicited using green Ganzfeld flashes (11.38 scd/m(2), 22.76 cds/m(2)) and a rod suppressing green-background (40 cd/m(2)). PhNRs were compared before and after optic nerves were transected. Cresyl violet stained retinal flatmounts were used to estimate cell loss in the ganglion cell layer 3 and 15 weeks after optic nerve transection. The pharmacological effect of 1.3 microM intravitreal TTX on the PhNR was also evaluated. RESULTS There was a significant loss (p <0.05) in the PhNR of 20, 36, 34, 35, 48, 48 and 56% for ONTx eye versus the contralateral eye, at post ONTx times of 24 h, 1, 2, 3, 4, 8 and 15 weeks. B-wave amplitudes of ONTx eyes were not significantly different from the control eyes. In ONTx eyes, mean cell loss in the retinal ganglion cell layer was 27 and 55% at the 3 week and 15 week time periods. In the eyes with ONTx, the decline of PhNR amplitudes was correlated positively with RGC loss (r = 0.98; p < 0.01). Thirty minutes after intravitreal TTX injection, the PhNR was significantly reduced (57%, p<0.01). CONCLUSIONS There was a time-dependent decline in the PhNR after ONTx, as exemplified by a 35% reduction from 1-3 weeks, a 48% decline for 4-8 weeks and a 56% decline after 15 weeks. The correlation between the decline in the PhNR and retinal ganglion cell loss suggests that the PhNR depends on inner retina integrity and the PhNR may be important biological signal or detecting glaucomatous damage and the monitoring of RGC function changes in early glaucoma.
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Affiliation(s)
- B Li
- Alcon Research Ltd., Fort Worth, TX 76134, USA.
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Abstract
The Purkinje cell of the cerebellar cortex presents two distinct dendritic domains: a distal one, with spiny branchlets and a high density of spines innervated by many parallel fibers, and a proximal one, with a few clusters of spines innervated by a single climbing fiber terminal arbor. In adult rats, after 7 days of blocked electrical activity by the administration of TTX into the cerebellar parenchyma, the proximal dendritic domain of the Purkinje cell shows a remarkable growth of new spines that are innervated by parallel fibers. At the same time, the climbing fiber terminal arbor tends to become atrophic. In contrast, in the branchlets, spine density remains unmodified. These changes are reversible when TTX is removed. TTX treatment also leads to a decrease in spine size both in the branchlets and in the new spines of the proximal dendritic compartment. Spontaneous electrical activity should therefore be regarded not simply as noise, but as a significant signal for maintaining the typical profile of afferent innervation of the Purkinje cell and for preventing spines from shrinking.
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Affiliation(s)
- Laura Morando
- Rita Levi Montalcini Center for Brain Repair, Department of Neuroscience, University of Turin, Italy
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Hara H, Takeno K, Shimogori H, Yamashita H. CGRP Expression in the Vestibular Periphery after Transient Blockage of Bilateral Vestibular Input. ORL J Otorhinolaryngol Relat Spec 2005; 67:259-65. [PMID: 16374057 DOI: 10.1159/000089405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
This study aimed to establish an animal model of reversible bilateral vestibular disorders that is suitable for examining the mechanisms of vestibular plasticity, and to observe the changes in the plasticity of vestibular efferent systems. Tetrodotoxin (TTX) was infused continuously for 7 days into the bilateral perilymph of guinea pig cochlea. We assessed the vestibulo-ocular reflex (VOR) for evaluating the vestibular function. We also investigated the changes in calcitonin gene-related peptide (CGRP) immunoreactivity in vestibular end organs to observe the changes in the plasticity of vestibular systems. The VOR was completely eliminated by TTX administration and returned to the preoperative levels within 120 h after TTX discontinuation. An obvious increase in the number of CGRP-immunoreactive fibers was observed within the neurosensory epithelia of the maculae and cristae. An animal model of reversible bilateral vestibular disorders was established and used for investigating the plasticity of the vestibular nervous system.
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Affiliation(s)
- Hirotaka Hara
- Department of Otolaryngology, Yamaguchi University School of Medicine, Ube, Yamaguchi, Japan.
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Cimadevilla JM, Miranda R, López L, Arias JL. Partial unilateral inactivation of the dorsal hippocampus impairs spatial memory in the MWM. ACTA ACUST UNITED AC 2005; 25:741-6. [PMID: 16216479 DOI: 10.1016/j.cogbrainres.2005.09.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 07/23/2005] [Accepted: 09/03/2005] [Indexed: 12/18/2022]
Abstract
The hippocampus is one of the more widely studied structures related with spatial memory. In this study, we assessed the effect of unilateral inactivation of the dorsal hippocampus with tetrodotoxin (TTX) on the performance displayed by Wistar rats in the spatial version of the Morris water maze. In experiment 1, we injected into the dorsal hippocampus in two different groups of rats 1 microl of saline solution or 5 ng of TTX in 1 microl of saline each day immediately after the training during four consecutive days. This procedure blocked consolidation and impaired spatial memory in the TTX group. In experiment 2, a new group of subjects was trained in the Morris water maze for 8 days and was administered 1 microl of saline on day 7 (saline session) and TTX on day 8 (TTX session) into the dorsal hippocampus 40 min before the training. Only the treatment with TTX altered the retrieval of memories. These experiments showed that unilateral interventions on the dorsal hippocampus can affect consolidation as well as retrieval of well-established spatial memories.
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Affiliation(s)
- José M Cimadevilla
- Department of Neuroscience, University of Almeria, 04120 Almeria, Spain.
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Lalonde MR, Chauhan BC, Tremblay F. Retinal ganglion cell activity from the multifocal electroretinogram in pig: optic nerve section, anaesthesia and intravitreal tetrodotoxin. J Physiol 2005; 570:325-38. [PMID: 16284074 PMCID: PMC1464311 DOI: 10.1113/jphysiol.2005.098046] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Non-invasive recordings of the retinal activity have an important role to play in the diagnosis of retinal pathologies. The detection of diseases that involve retinal ganglion cells (RGCs), such as optic atrophy and glaucoma, may be improved by isolating the RGC contribution from the multifocal electroretinogram (mfERG). In this study, mfERGs were performed on 20 pigs, 1-6 weeks following unilateral retrobulbar optic nerve section (ONS). The stimuli were 103 non-scaled high-contrast hexagons from which summed and individual mfERG responses were obtained in experimental and control fellow eyes under conditions of ketamine (n = 11) or isoflurane anaesthesia (n = 9). The effect of intravitreal injection of tetrodotoxin (TTX; n = 6) was also investigated. The summed mfERG responses showed a first positive peak (P1) with a short latency (21 ms) followed by two smaller peaks (P2 and P3) of longer latency (46 and 65 ms, respectively). While P2 and P3 amplitude were highly correlated with the time post-optic nerve section (ONS) (P2: r(2) = 0.669; P = 0.007; P3: r(2) = 0.651; P = 0.005), P1 was not (r(2) = 0.193; P = 0.38). P1 and P2 showed no implicit time variation as a function of retinal location, while P3 implicit time varied along the axis of the visual streak, generating a naso-temporal asymmetry. However, the P3 implicit time did not vary consistently with distance away from the optic nerve head. Intravitreal injections of TTX reduced P2 and P3 in the control eyes, consistent with the effect of ONS, and also induced a series of regular oscillations lasting up to 200 ms post stimulus. Under isoflurane anaesthesia, all components of the mfERG ifn experimental and control eyes were, at all time points post-ONS, of similar amplitude and without naso-temporal asymmetry, suggesting a reduced participation of RGCs under these anaesthesic conditions. These data clearly demonstrate that it is possible to isolate the RGC contribution from non-invasive multifocal electroretinography.
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Affiliation(s)
- Mélanie R Lalonde
- Retina and Optic Nerve Research Laboratory, Dalhousie University, Halifax, Nova Scotia, Canada
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Abstract
Herpes simplex virus types 1 and 2 (HSV-1, -2) infect and also establish latency in neurons. In the present study, the authors investigated the influence of neuronal activity on the replication of HSV-1. The results showed that the sodium channel blocker tetrodotoxin (TTX) and the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) could significantly increase viral replication in primary neuronal cultures, by two- to fourfold. In contrast, KCl reduced viral production by at least 80% in the same cultures. Inhibitors of GABA(A) receptors completely abolished the effects of GABA. Intravitreously injected TTX in a mouse corneal scarification model enhanced the viral titers > 10-fold in both the trigeminal ganglia and the brain. At 2 h post infection, both TTX and GABA significantly up-regulated the levels of transcription for the viral immediate early (IE) genes ICP0, ICP4, and ICP27, as revealed by real time PCR. These results indicate that the neuronal excitation status may dictate the efficiency of HSV-1 viral replication, probably by regulating the levels of viral IE gene expression. These are the first findings connecting neuronal activity to the molecular mechanisms of HSV replication in the nervous system, which may significantly influence our view of herpesvirus infection and latency.
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Affiliation(s)
- Cheryl X Zhang
- Department of Surgery and Brain Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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Abstract
STUDY OBJECTIVES To determine the effects of temporary functional inactivation of the central nucleus of the amygdala on sleep and on activity in an arousing environment, an open field. DESIGN Rats were implanted with electrodes for recording the electroencephalogram (EEG) and electromyogram (EMG), and with guide cannulae aimed into CNA. Sleep was recorded for 22 h (10 h light, 12 h dark) following microinjections of tetrodotoxin (TTX: 5.0 ng/0.2 microl given unilaterally [TTXUH] or bilaterally [TTXBH], and 2.5 ng/0.1 microl given bilaterally [TTXBL]) or saline (SAL) alone on separate days. Activity during 1 h in an OF was recorded after microinjections of TTXBH and SAL. SETTING NA. PATIENTS OR PARTICIPANTS Three-month-old Wistar rats (n=12). INTERVENTIONS Functional inactivation of the central nucleus of the amygdala with TTX. MEASUREMENTS AND RESULTS Compared to SAL, all TTX microinjections significantly shortened NREM latency, but did not alter total NREM during either light or dark periods. During the light period, TTXBH significantly reduced total REM and REM episode number, and TTXBL decreased REM episode number. All TTX microinjections increased EEG slow wave activity (0.5-4 Hz, SWA) during wakefulness, NREM and REM. Activity in OF was decreased after TTXBH compared to SAL. CONCLUSIONS Functional lesions of the amygdala, including the central nucleus of the amygdala, decreased REM sleep and reduced arousal, as indicated by shortened NREM latency and decreased activity in an arousing environment. These findings suggest that the amygdala plays a broad role in modulating spontaneous sleep and wakefulness and in modulating responsiveness in arousing situations.
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Affiliation(s)
- Xiangdong Tang
- Sleep Research Laboratory, Department of Pathology and Anatomy, Eastern Virginia Medical School, P.O. Box 1980, Norfolk, VA 23501, USA.
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Fernández-Pastor B, Mateo Y, Gómez-Urquijo S, Javier Meana J. Characterization of noradrenaline release in the locus coeruleus of freely moving awake rats by in vivo microdialysis. Psychopharmacology (Berl) 2005; 180:570-9. [PMID: 15717207 DOI: 10.1007/s00213-005-2181-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2004] [Accepted: 01/10/2005] [Indexed: 11/26/2022]
Abstract
RATIONALE The origin and regulation of noradrenaline (NA) in the locus coeruleus (LC) is unknown. OBJECTIVES The neurochemical features of NA overflow (nerve impulse dependence, neurotransmitter synthesis, vesicle storage, reuptake, alpha2-adrenoceptor-mediated regulation) were characterized in the LC. METHODS Brain microdialysis was performed in awake rats. Dialysates were analyzed for NA. RESULTS NA in the LC decreased via local infusion of Ca2+-free medium (-42+/-5%) or the sodium channel blocker tetrodotoxine (TTX) (-47+/-8%) but increased (333+/-40%) via KCl-induced depolarization. The tyrosine hydroxylase (TH) inhibitor alpha-methyl-p-tyrosine (250 mg kg(-1), i.p.) and the vesicle depletory drug reserpine (5 mg kg(-1), i.p.) decreased NA. Therefore, extracellular NA in the LC satisfies the criteria for an impulse flow-dependent vesicular exocytosis of neuronal origin. Local perfusion of the alpha2-adrenoceptor agonist clonidine (0.1-100 microM) decreased NA (E(max)=-79+/-5%) in the LC, whereas the opposite effect (E(max)=268+/-53%) was observed with the alpha2A-adrenoceptor antagonist BRL44408 (0.1-100 microM). This suggests a tonic modulation of NA release through local alpha2A-adrenoceptors. The selective NA reuptake inhibitor desipramine (DMI) (0.1-100 microM) administered into the LC increased NA in the LC (E(max)=223+/-40%) and simultaneously decreased NA in the cingulate cortex, confirming the modulation exerted by NA in the LC on firing activity of noradrenergic cells and on the subsequent NA release in noradrenergic terminals. CONCLUSION Synaptic processes underlying NA release in the LC are similar to those in noradrenergic terminal areas. NA in the LC could represent local somatodendritic release, but also the presence of neurotransmitter release from collateral axon terminals.
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Hasegawa H, Ishiwata T, Saito T, Yazawa T, Aihara Y, Meeusen R. Inhibition of the preoptic area and anterior hypothalamus by tetrodotoxin alters thermoregulatory functions in exercising rats. J Appl Physiol (1985) 2005; 98:1458-62. [PMID: 15618320 DOI: 10.1152/japplphysiol.00916.2004] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have previously demonstrated a functional role of the preoptic area and anterior hypothalamus (PO/AH) in thermoregulation in freely moving rats at various temperature conditions by using microdialysis and biotelemetry methods. In the present study, we perfused tetrodotoxin (TTX) solution into the PO/AH to investigate whether this manipulation can modify thermoregulation in exercising rats. Male Wistar rats were trained for 3 wk by treadmill running. Body core temperature (Tb), heart rate (HR), and tail skin temperature (Ttail) were measured. Rats ran for 120 min at speed of 10 m/min, with TTX (5 μM) perfused into the left PO/AH during the last 60 min of exercise through a microdialysis probe (control, n = 12; TTX, n = 12). Tb, HR, and Ttail increased during the first 20 min of exercise. Thereafter, Tb, HR, and Ttail were stable in both groups. Perfusion of TTX into the PO/AH evoked an additional rise in Tb (control: 38.2 ± 0.1°C, TTX: 39.3 ± 0.2°C; P < 0.001) with a significant decrease in Ttail (control: 31.2 ± 0.5°C, TTX: 28.3 ± 0.7°C; P < 0.01) and a significant increase in HR (control: 425.2 ± 12 beats/min, TTX: 502.1 ± 13 beats/min; P < 0.01). These results suggest that the TTX-induced hyperthermia was the result of both an impairment of heat loss and an elevation of heat production during exercise. We therefore propose the PO/AH as an important thermoregulatory site in the brain during exercise.
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Affiliation(s)
- Hiroshi Hasegawa
- Dept. of Human Physiology and Sportsmedicine, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
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Abstract
Songbirds learn their songs by trial-and-error experimentation, producing highly variable vocal output as juveniles. By comparing their own sounds to the song of a tutor, young songbirds gradually converge to a stable song that can be a remarkably good copy of the tutor song. Here we show that vocal variability in the learning songbird is induced by a basal-ganglia-related circuit, the output of which projects to the motor pathway via the lateral magnocellular nucleus of the nidopallium (LMAN). We found that pharmacological inactivation of LMAN dramatically reduced acoustic and sequence variability in the songs of juvenile zebra finches, doing so in a rapid and reversible manner. In addition, recordings from LMAN neurons projecting to the motor pathway revealed highly variable spiking activity across song renditions, showing that LMAN may act as a source of variability. Lastly, pharmacological blockade of synaptic inputs from LMAN to its target premotor area also reduced song variability. Our results establish that, in the juvenile songbird, the exploratory motor behavior required to learn a complex motor sequence is dependent on a dedicated neural circuit homologous to cortico-basal ganglia circuits in mammals.
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Affiliation(s)
- Bence P Ölveczky
- 1McGovern Institute for Brain Research, Department of Brain and Cognitive SciencesMassachusetts Institute of Technology, Cambridge, MassachusettsUnited States of America
- 2Harvard Society of Fellows, Harvard UniversityCambridge, MassachusettsUnited States of America
| | - Aaron S Andalman
- 1McGovern Institute for Brain Research, Department of Brain and Cognitive SciencesMassachusetts Institute of Technology, Cambridge, MassachusettsUnited States of America
| | - Michale S Fee
- 1McGovern Institute for Brain Research, Department of Brain and Cognitive SciencesMassachusetts Institute of Technology, Cambridge, MassachusettsUnited States of America
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Yamamori K, Kono M, Furukawa K, Matsui T. [The toxification of juvenile cultured kusafugu Takifugu niphobles by oral administration of crystalline tetrodotoxin]. Shokuhin Eiseigaku Zasshi 2004; 45:73-5. [PMID: 15272603 DOI: 10.3358/shokueishi.45.73] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Non-toxic cultured juvenile kusafugu were fed with diet containing crystalline tetrodotoxin (TTX) for 30 days and then fed with non-toxic diet for 170 days. During this period, 5 fish were sampled and the toxicity of each tissue was determined periodically. The amount of total accumulated toxin in the fish was 90 microg, representing 50% of the administered TTX (180 microg/fish) at the 60th day. It decreased to 54 microg (30%) at the 80th day and then remained unchanged up to the 200th day. The amount of toxin in the liver amounted to 40 microg (45% of total accumulated toxin) at the 30th day and gradually decreased to 5 microg (10%) at the 200th day. The toxin amount in the skin reached the highest level with 30 microg (30%) at the 50th day and then remained unchanged during the experimental period. The testes had almost no toxicity. Although the ovaries were immature, the toxin amounts increased as the weight of the tissues increased. With administration of crystalline TTX, all kusafugu used in the experiment became toxic and retained the toxin at the level of 30% of the administered toxin for about 5 months thereafter, while being fed with non-toxic diet.
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Affiliation(s)
- Kunio Yamamori
- School of Fisheries Sciences, Kitasato University, 160-4, Sanriku-cho, Ofunato, Iwate 022-0101, Japan
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Paul KN, Gamble KL, Fukuhara C, Novak CM, Tosini G, Albers HE. Tetrodotoxin administration in the suprachiasmatic nucleus prevents NMDA-induced reductions in pineal melatonin without influencing Per1 and Per2 mRNA levels. Eur J Neurosci 2004; 19:2808-14. [PMID: 15147314 DOI: 10.1111/j.0953-816x.2004.03387.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The suprachiasmatic nucleus (SCN) of the anterior hypothalamus contains a light-entrainable circadian pacemaker. Neurons in the SCN are part of a circuit that conveys light information from retinal efferents to the pineal gland. Light presented during the night acutely increases mRNA levels of the circadian clock genes Per1 and Per2 in the SCN, and acutely suppresses melatonin levels in the pineal gland. The present study investigated whether the ability of light to increase Per1 and Per2 mRNA levels and suppress pineal melatonin levels requires sodium-dependent action potentials in the SCN. Per1 and Per2 mRNA levels in the SCN and pineal melatonin levels were measured in Syrian hamsters injected with tetrodotoxin (TTX) prior to light exposure or injection of N-methyl-D-aspartate (NMDA). TTX inhibited the ability of light to increase Per1 and Per2 mRNA levels and suppress pineal melatonin levels. TTX did not, however, influence the ability of NMDA to increase Per1 and Per2 mRNA levels, though it did inhibit the ability of NMDA to suppress pineal melatonin levels. These results demonstrate that action potentials in the SCN are not necessary for NMDA receptor activation to increase Per1 and Per2 mRNA levels, but are necessary for NMDA receptor activation to decrease pineal melatonin levels. Taken together, these data support the hypothesis that the mechanism through which light information is conveyed to the pacemaker in the SCN is separate from and independent of the mechanism through which light information is conveyed to the SCN cells whose efferents suppress pineal melatonin levels.
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Affiliation(s)
- Ketema N Paul
- Center for Behavioural Neuroscience, and Department of Biology, Georgia State University, Atlanta, 30303, USA.
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49
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Abstract
In acute brain disorders, elimination of the excitatory output from an injured brain region reduces activity in connecting brain regions remote from the lesion site (i.e., diaschisis). The authors examined the effect of functional ablation of the left cerebral cortex by cortical spreading depression (CSD) or topical application of tetrodotoxin on single cell spiking activity, baseline CBF, and neurovascular coupling in the right rat sensory cortex. CSD or tetrodotoxin in left cortex reduced the right cortical spontaneous spike rate by 36% and 45%, respectively. Baseline CBF in the right cortex was unaffected by a left-sided CSD, but decreased by 12% for left cortical application of tetrodotoxin. This suggested dissociation between spontaneous spiking activity and basal CBF. Left in-fraorbital nerve stimulation evoked local field potentials in right cerebral cortex that were reduced in amplitude by 19% for left CSD and by 23% for left tetrodotoxin application. The corresponding declines in the evoked CBF responses were 42% for CSD and 23% for tetrodotoxin. Vascular reactivity to adenosine remained unchanged in right cortex. Thus, transhemispheric diaschisis produced a pronounced decrease in the spontaneous spike rate accompanied by no reduction or a small reduction in basal CBF, and an attenuation in amplitudes of evoked synaptic responses and corresponding rises in CBF. The findings suggest that disturbed neurovascular coupling may contribute to the disturbance in brain function in acute transhemispheric diaschisis.
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Affiliation(s)
- Pia Enager
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, Copenhagen, Denmark
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Abstract
PURPOSE Mossy fiber sprouting is a common abnormality found in patients and models of temporal lobe epilepsy. The role of mossy fiber sprouting in epileptogenesis is unclear, and its blockade would be useful experimentally and perhaps therapeutically. Results from previous attempts to block mossy fiber sprouting have been disappointing or controversial. In some brain regions, prolonged application of the sodium channel blocker tetrodotoxin prevents axon sprouting and posttrauma epileptogenesis. The present study tested the hypothesis that prolonged, focal infusion of tetrodotoxin would block mossy fiber sprouting after an epileptogenic treatment. METHODS Adult rats were treated with pilocarpine to induce status epilepticus. Several hours to 3 days after pilocarpine treatment, a pump with a cannula directed toward the dentate gyrus was implanted to deliver 10 microM tetrodotoxin or vehicle alone at 0.25 microl/h. This method blocks local EEG activity in the hippocampus (Galvan et al. J Neurosci 2000; 20:2904-16). After 28 days of continuous infusion, rats were perfused with fixative, and their hippocampi analyzed anatomically with stereologic techniques. RESULTS Tetrodotoxin infusion was verified immunocytochemically in tetrodotoxin-treated but not vehicle-treated hippocampi. Tetrodotoxin-infused and vehicle-infused hippocampi displayed similar levels of hilar neuron loss. The Timm stain revealed mossy fiber sprouting regardless of whether hippocampi were treated with tetrodotoxin infusion, vehicle infusion, or neither. CONCLUSIONS Prolonged infusion of tetrodotoxin did not block mossy fiber sprouting. This finding suggests that sodium channel-mediated neuronal activity is not necessary for mossy fiber sprouting after an epileptogenic treatment.
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Affiliation(s)
- Paul S Buckmaster
- Department of Comparative Medicine, Stanford University, Palo Alto, California 94305-5342, USA.
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