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Ibarra-Vega R, Jiménez-Vargas JM, Pineda-Contreras A, Martínez-Martínez FJ, Barajas-Saucedo CE, García-Ortega H, Magaña-Vergara NE, Possani LD, Corzo G, Gaitan-Hinojosa MA, Vázquez-Vuelvas OF, Zamudio F, Valdez-Velazquez LL. Indolealkylamines in the venom of the scorpion Thorellius intrepidus. Toxicon 2023; 233:107232. [PMID: 37536653 DOI: 10.1016/j.toxicon.2023.107232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 07/14/2023] [Accepted: 07/30/2023] [Indexed: 08/05/2023]
Abstract
Scorpions are a group of arthropods that strike fear in many people due to their severe medical symptoms, even death, caused by their venomous stings. Even so, not all scorpion species contain harmful venoms against humans but still have valuable bioactive molecules, which could be used in developing new pharmaceutical leads for treating important diseases. This work conducted a comprehensive analysis of the venom from the scorpion Thorellius intrepidus. The venom of T. intrepidus was separated by size exclusion chromatography, and four main fractions were obtained. Fraction IV (FIV) contained small molecules representing over 90% of the total absorbance at 280 nm. Analysis of fraction FIV by RP-HPLC indicated the presence of three main molecules (FIV.1, FIV.2, and FIV.3) with similar UV absorbance spectra profiles. The molecular masses of FIV.1, FIV.2, and FIV.3 were determined, resulting in 175.99, 190.07, and 218.16 Da, respectively. Further confirmation through 1H-NMR and 13C-NMR analyses revealed that these molecules were serotonin, N-methylserotonin, and bufotenidine. These intriguing compounds are speculated to play a pivotal role in self-defense and increasing venom toxicity and could also offer promising biotechnological applications as small bioactive molecules.
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Affiliation(s)
- Rodrigo Ibarra-Vega
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México
| | - Juana María Jiménez-Vargas
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México; Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCYT), México City, 03940, México.
| | - Armando Pineda-Contreras
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México
| | | | - Carlos Eduardo Barajas-Saucedo
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México
| | - Héctor García-Ortega
- Facultad de Química, Universidad Nacional Autónoma de México, 04510, Ciudad de México, México
| | - Nancy E Magaña-Vergara
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México; Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCYT), México City, 03940, México
| | - Lourival D Possani
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Morelos, México
| | - Gerardo Corzo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Morelos, México
| | - Mario Alberto Gaitan-Hinojosa
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México
| | - Oscar Fernando Vázquez-Vuelvas
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México
| | - Fernando Zamudio
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Morelos, México
| | - Laura Leticia Valdez-Velazquez
- Facultad de Ciencias Químicas, Universidad de Colima, Carretera Colima-Coquimatlán Km 9, 28400, Coquimatlán, Colima, México.
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2
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Martinello K, Sucapane A, Fucile S. 5-HT3 Receptors in Rat Dorsal Root Ganglion Neurons: Ca 2+ Entry and Modulation of Neurotransmitter Release. LIFE (BASEL, SWITZERLAND) 2022; 12:life12081178. [PMID: 36013357 PMCID: PMC9409985 DOI: 10.3390/life12081178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 07/29/2022] [Accepted: 07/31/2022] [Indexed: 11/16/2022]
Abstract
Rat dorsal root ganglion (DRG) neurons express 5-hydroxytryptamine receptors (5-HT3Rs). To elucidate their physiological role in the modulation of sensory signaling, we aimed to quantify their functional expression in newborn and adult rat DRG neurons, as well as their ability to modulate the Ca2+-dependent neurotransmitter release, by means of electrophysiological techniques combined with fluorescence-based Ca2+ imaging. The selective 5-HT3R agonist mCPBG (10 μM) elicited whole-cell currents in 92.5% of adult DRG neurons with a significantly higher density current than in responding newborn cells (52.2%), suggesting an increasing serotoninergic modulation on primary afferent cells during development. Briefly, 5-HT3Rs expressed by adult DRG neurons are permeable to Ca2+ ions, with a measured fractional Ca2+ current (i.e., the percentage of total current carried by Ca2+ ions, Pf) of 1.0%, similar to the value measured for the human heteromeric 5-HT3A/B receptor (Pf = 1.1%), but lower than that of the human homomeric 5-HT3A receptor (Pf = 3.5%). mCPBG applied to co-cultures of newborn DRG and spinal neurons significantly increased the miniature excitatory postsynaptic currents (mEPSCs) frequency in a subset of recorded spinal neurons, even in the presence of Cd2+, a voltage-activated Ca2+ channel blocker. Considered together, our findings indicate that the Ca2+ influx through heteromeric 5-HT3Rs is sufficient to increase the spontaneous neurotransmitter release from DRG to spinal neurons.
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Affiliation(s)
| | - Antonietta Sucapane
- Department of Physiology and Pharmacology, Sapienza University of Rome, P.le Aldo Moro, 5, 00185 Rome, Italy;
| | - Sergio Fucile
- IRCCS Neuromed, Via Atinense, 86077 Pozzilli, Italy;
- Department of Physiology and Pharmacology, Sapienza University of Rome, P.le Aldo Moro, 5, 00185 Rome, Italy;
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3
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Lu H, Liu QS. Serotonin in the Frontal Cortex: A Potential Therapeutic Target for Neurological Disorders. ACTA ACUST UNITED AC 2017; 6. [PMID: 28758051 PMCID: PMC5531193 DOI: 10.4172/2167-0501.1000e184] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hui Lu
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Qing-Song Liu
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, W 53226, USA
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4
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Abstract
Dopamine is a critical neuromodulator that activates GPCRs in mammals or ligand-gated ion channels in invertebrates. The present study demonstrates that dopamine (0.1-10 mm) exerts novel, opposing effects on different populations of mammalian (rat) GABAA receptors. Using whole-cell patch-clamp electrophysiology, we observed direct dopamine-mediated inhibition of tonic-level (1 μm) GABA-evoked currents in untransfected striatal neurons that could be recapitulated in HEK293 cells containing α1β3 or α1β2γ2 subunits. Surprisingly, direct activation by dopamine was seen in the absence of GABA with α1β2γ2, α5β3γ2, or α1β3γ2 transfections. This activity was also present in α1β3γ2 receptors containing a mutant β3 subunit (H267A [(Z)β3]) insensitive to trace levels of inhibitory Zn(2+). Dopamine activation required β and γ subunits but not α subunits ((Z)β3γ2 EC50 value, 660 μm). Dopamine activity was fully blocked by picrotoxin but not GABAA competitive antagonists, and was strongly correlated with spontaneous receptor activity. We also report opposing effects of bicuculline and gabazine, such that bicuculline surprisingly activated non-α-containing (β3γ2) GABAA receptors, whereas gabazine suppressed spontaneous activity in these receptors. Our results suggest that dopamine may directly inhibit GABAA receptors that are both immediately adjacent to dopamine release sites in the striatum and activated by tonic GABA. Furthermore, synaptic/phasic release of dopamine may directly enhance signaling at some spontaneously active noncanonical GABAA receptors that lack α subunits.
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5
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Ishigami T, Yoshioka K, Karicheti V, Marson L. A Role for Peripheral 5-HT2 Receptors in Serotonin-Induced Facilitation of the Expulsion Phase of Ejaculation in Male Rats. J Sex Med 2013; 10:2688-702. [DOI: 10.1111/jsm.12306] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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6
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Gataullin RR. Advances in the synthesis of cycloalka[b]indoles. RUSSIAN JOURNAL OF ORGANIC CHEMISTRY 2013. [DOI: 10.1134/s1070428013020012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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7
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Tomooka K, Iso C, Uehara K, Suzuki M, Nishikawa-Shimono R, Igawa K. Planar-Chiral [7]Orthocyclophanes. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204484] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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8
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Tomooka K, Iso C, Uehara K, Suzuki M, Nishikawa-Shimono R, Igawa K. Planar-Chiral [7]Orthocyclophanes. Angew Chem Int Ed Engl 2012; 51:10355-8. [DOI: 10.1002/anie.201204484] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Indexed: 11/10/2022]
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9
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10
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Bouchoucha M, Uzzan B, Cohen R. Metformin and digestive disorders. DIABETES & METABOLISM 2011; 37:90-6. [DOI: 10.1016/j.diabet.2010.11.002] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2010] [Revised: 10/22/2010] [Accepted: 11/03/2010] [Indexed: 12/22/2022]
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11
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Ajioka H, Morita F, Akizawa Y, Yoshida K, Kitamura R, Takimoto H. [Pharmacological, pharmacokinetic, and clinical profile of palonosetron hydrochloride (ALOXI I.V. Injection 0.75 mg), a novel antiemetic 5-HT3-receptor antagonist]. Nihon Yakurigaku Zasshi 2010; 136:113-120. [PMID: 20702972 DOI: 10.1254/fpj.136.113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
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12
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Langlois M, Yang D, Soulier JL, Florac C. Synthesis of Derivatives of 1, 2, 6-Trisubstttuted-4-Piperidones. SYNTHETIC COMMUN 2009. [DOI: 10.1080/00397919209409262] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
| | - Donglaï Yang
- a CNRS-CERCOA , 2-8 rue, Henri , Dunant , F-94320 , THIAIS
| | | | - Claudie Florac
- a CNRS-CERCOA , 2-8 rue, Henri , Dunant , F-94320 , THIAIS
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13
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Stewart GW, Baxter CA, Cleator E, Sheen FJ. A Mild and Efficient One-Pot Synthesis of 2-Aminated Benzoxazoles and Benzothiazoles. J Org Chem 2009; 74:3229-31. [DOI: 10.1021/jo900308t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gavin W. Stewart
- Department of Process Research, Merck Sharp & Dohme Research Laboratories, Hertford Road, Hoddesdon, Hertfordshire, EN11 9BU, United Kingdom
| | - Carl A. Baxter
- Department of Process Research, Merck Sharp & Dohme Research Laboratories, Hertford Road, Hoddesdon, Hertfordshire, EN11 9BU, United Kingdom
| | - Ed Cleator
- Department of Process Research, Merck Sharp & Dohme Research Laboratories, Hertford Road, Hoddesdon, Hertfordshire, EN11 9BU, United Kingdom
| | - Faye J. Sheen
- Department of Process Research, Merck Sharp & Dohme Research Laboratories, Hertford Road, Hoddesdon, Hertfordshire, EN11 9BU, United Kingdom
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14
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Hascoët M, Bourin M. The Mouse Light–Dark Box Test. MOOD AND ANXIETY RELATED PHENOTYPES IN MICE 2009. [DOI: 10.1007/978-1-60761-303-9_11] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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15
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Zefirova ON, Zefirov NS. Physiologically active compounds interacting with serotonin (5-hydroxytryptamine) receptors. RUSSIAN CHEMICAL REVIEWS 2007. [DOI: 10.1070/rc2001v070n04abeh000654] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Hu DL, Zhu G, Mori F, Omoe K, Okada M, Wakabayashi K, Kaneko S, Shinagawa K, Nakane A. Staphylococcal enterotoxin induces emesis through increasing serotonin release in intestine and it is downregulated by cannabinoid receptor 1. Cell Microbiol 2007; 9:2267-77. [PMID: 17517065 DOI: 10.1111/j.1462-5822.2007.00957.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Staphylococcal enterotoxins (SEs) produced by Staphylococcus aureus are the most recognizable bacterial superantigenic toxins causing food poisoning in humans throughout the world. However, it remains unclear how SEs induce emesis and its emetic signal pathway. We investigated a mechanism of SEA-induced emesis using a small emetic animal model, house musk shrew. SEA-induced emesis in the animals was inhibited by a 5-hydroxytryptamine (5-HT) synthesis inhibitor and a 5-HT(3) receptor antagonist. SEA could increase 5-HT release in the small intestine. Pre-treatment with 5,7-dihydroxytryptamine (5,7-DHT) markedly inhibited SEA-induced emesis. SEA-induced emesis was also abolished by surgical vagotomy. Furthermore, cannabinoid (CB) receptor agonists inhibited SEA-induced emesis, and the action was reversed by a CB1 antagonist. Both 5-HT release and CB1 receptor expression were found in the mucosal and myenteric plexus of the intestine. Moreover, a CB1 receptor agonist significantly decreased the 5-HT release in the intestine. These results demonstrate that SEA induces 5-HT release in intestine, rather than in brain, and that the 5-HT(3) receptors on vagal afferent neurons are essential for SEA-stimulated emesis. In addition, SEA-induced emesis is downregulated by the CB system through decreasing 5-HT release in intestine.
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Affiliation(s)
- Dong-Liang Hu
- Department of Microbiology and Immunology, Hirosaki University School of Medicine, Hirosaki, Japan
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17
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Yoshida S, Watanabe T, Sato Y. Regulatory molecules for the 5-HT3 receptor ion channel gating system. Bioorg Med Chem 2007; 15:3515-23. [PMID: 17391967 DOI: 10.1016/j.bmc.2007.02.054] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 02/23/2007] [Accepted: 02/27/2007] [Indexed: 01/05/2023]
Abstract
Substituted benzoxazole derivatives which possess a nitrogen-containing heterocycle at C2 are selective partial agonists of the 5-HT(3) receptor. Alteration of substituents on the benzoxazole nucleus affords both agonist-like and antagonist-like compounds, and uniquely modifies the function of the 5-HT(3) receptor ion channel gating system. SAR and corroborative computational docking study for these partial agonists successfully explained structure and function of the 5-HT(3) receptor.
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Affiliation(s)
- Satoshi Yoshida
- Pharmaceutical Research Department, Meiji Seika Kaisha Ltd, Yokohama 222-8567, Japan.
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18
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Dukat M, Wesołowska A. Antinociception: Mechanistic studies on the action of MD-354 and clonidine. Part 1. The 5-HT3 component. Eur J Pharmacol 2005; 528:59-64. [PMID: 16321376 DOI: 10.1016/j.ejphar.2005.10.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 10/18/2005] [Accepted: 10/25/2005] [Indexed: 11/24/2022]
Abstract
MD-354 (m-chlorophenylguanidine) is a 5-HT3/alpha2B-adrenoceptor ligand. Both receptors play a role in antinociception. In the mouse tail-flick assay, subcutaneously administered MD-354 was inactive as an analgesic. However, a combination of an inactive dose of clonidine (0.25 mg/kg) with an inactive dose of MD-354 (6 mg/kg) produced a substantial antinociceptive effect (maximal possible effect=66%). Considering the 5-HT3 receptor partial agonist properties of MD-354, the analgesia enhancing effect of MD-354 on clonidine might be associated, at least in part, with its 5-HT3 receptor agonist or antagonist activity. Combinations of an inactive dose of clonidine (0.25 mg/kg) with 5-HT3 receptor antagonists (tropisetron, zacopride and ondansetron) were examined. Saline-like doses of tropisetron, zacopride and ondansetron significantly enhanced the antinociceptive effect of clonidine (combinations: maximal possible effect=86%, 82% and 79% respectively), suggesting that MD-354 may enhance the analgesic actions of clonidine, at least in part, through a 5-HT3 receptor antagonist mechanism.
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Affiliation(s)
- Magorzata Dukat
- Department of Medicinal Chemistry, School of Pharmacy, Box 980540 Virginia Commonwealth University, Richmond, VA 23298-0540, USA.
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19
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Yoshida S, Shiokawa S, Kawano KI, Ito T, Murakami H, Suzuki H, Sato Y. Orally Active Benzoxazole Derivative as 5-HT3 Receptor Partial Agonist for Treatment of Diarrhea-Predominant Irritable Bowel Syndrome. J Med Chem 2005; 48:7075-9. [PMID: 16250667 DOI: 10.1021/jm050209t] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
During our search for therapeutic agents to treat diarrhea-predominant IBS, we found that 2-substituted benzoxazole derivatives have a characteristic 5-HT(3) receptor partial agonist activity with high affinity. Some of these compounds showed high in vitro metabolical stability, and 6g showed marked antidiarrhetic activity with little side effect of constipation in in vivo tests. Our results indicate that 5-HT(3) receptor partial agonists might be superior as therapeutic agents to the drugs currently used for IBS treatment.
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Affiliation(s)
- Satoshi Yoshida
- Pharmaceutical Research Department, Meiji Seika Kaisha, Ltd., 760 Morooka-Cho, Kohoku-ku, Yokohama 222-8567, Japan.
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20
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Nakayama H, Yamakuni H, Higaki M, Ishikawa H, Imazumi K, Matsuo M, Mutoh S. Antiemetic activity of FK1052, a 5-HT3- and 5-HT4-receptor antagonist, in Suncus murinus and ferrets. J Pharmacol Sci 2005; 98:396-403. [PMID: 16079468 DOI: 10.1254/jphs.fpj05001x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
We investigated the effect of FK1052 [(+)-8,9-dihydro-10-methyl-7-[(5-methyl-1H-imidazol-4-yl)methyl]pyrido[1,2-a]indol-6(7H)-one hydrochloride], a 5-HT3- and 5-HT4-receptor antagonist, on the emesis induced by motion stimuli, copper sulfate, or cisplatin in either Suncus murinus or ferrets and also clarified the role of the 5-HT3 and 5-HT4 receptors in these models. In Suncus murinus, oral administration of FK1052 (100 microg/kg) completely prevented emesis induced by cisplatin (18 mg/kg, i.p.). Intraperitoneal injection of scopolamine (10 mg/kg) and promethazine (32 mg/kg), but not FK1052 (1 mg/kg), significantly reduced the emetic responses by motion stimuli. In ferrets, copper sulfate (40 mg/kg, p.o.)-induced emesis was moderately prevented by FK1052 (3.2 mg/kg), but not by granisetron (3.2 mg/kg). Cisplatin-induced acute (10 mg/kg, i.v.) and delayed (5 mg/kg, i.p.) emesis were significantly reduced by single and multiple intravenous injection of both FK1052 (3.2 mg/kg) and granisetron (3.2 mg/kg), respectively. The present study suggests that FK1052 may be useful against both acute and delayed emesis induced by cancer chemotherapy. Moreover, it is suggested that blockades of 5-HT3 and 5-HT4 receptors are not relevant to the control of motion sickness; and furthermore, it suggested that blocking 5-HT4 receptors in addition to 5-HT3 receptors does not have an additional effect on the control of cisplatin-induced emesis, but that 5-HT4 receptors are at least partly involved in the mechanism of emesis induced by copper sulfate.
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Affiliation(s)
- Hiroe Nakayama
- Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co., Ltd, Kashima 2-1-6, Osaka 532-8514, Japan
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Jeong SW, Cho JW, Hwang JS, Song JD, Shin S, Jang JY, Hwang SY, Kim O, Kim JC, Kim YB, Kang JK. The antiemetic effect of a novel tropisetron patch in anticancer agents-induced kaolin pica model using rats. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2005; 20:167-174. [PMID: 21783585 DOI: 10.1016/j.etap.2004.12.065] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2004] [Accepted: 12/12/2004] [Indexed: 05/31/2023]
Abstract
The efficacy of a novel transdermal patch containing tropisetron, a 5-hydroxytryptamine 3 (5-HT(3)) receptor antagonist, against emesis induced by anticancer agents were evaluated, in comparison with the effect of traditional tropisetron injection, in rats. The antiemetic effects were assessed via the inhibitory activity on the anticancer agent-induced kaolin-consuming behavior, a pica model representing vomiting in emesis-resistant rodents. The tropisetron patch (10mg/patch, 3.5cm(2)) was attached on the shaved back area of rats. Eight h later, each anticancer agent, cisplatin (10mg/kg, i.v.), cyclophosphamide (200mg/kg, i.p.) or doxorubicin (8mg/kg, i.v.), was administered, and thereafter, daily kaolin consumption was measured for 3 days. In comparison, the effect of daily injection of tropisetron (2mg/kg, i.v.), given 10min, 24 and 48h after the anticancer agent administration, was also evaluated. Kaolin intake greatly increased to 21, 17 and 10 folds of control ingestion on the first day after administration with the anticancer agents, cisplatin, cyclophosphamide and doxorubicin, respectively, and then gradually decreased to near control level on day 3. Such anticancer agent-induced increases in the kaolin consumption were remarkably attenuated by the attachment of tropisetron patch, resulting in the reduction to half levels, which is comparable to the efficacy of daily tropisetron injection. In particular, the blood concentration of tropisetron following patch attachment reached a maximum level of 30-40ng/ml in 12h and exhibited a plateau until detachment of the patch, in contrast to a rapid elimination with a half-life of 2.21h after injection of the drug. Taken together, it is suggested that the novel tropisetron patch could be a promising regimen for the relief of emesis, based on the long-term antiemetic effects on the diverse anticancer agents and the convenience to use the transdermal delivery system for the cancer patients who have difficulty in taking drugs due to surgical operation or gastrointestinal dysfunction.
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Affiliation(s)
- Seung Wei Jeong
- Research and Development Center, Samyang Co. Ltd., Hwaam-dong, Daejeon 305-717, Korea; College of Veterinary Medicine and Research Institute of Veterinary Medicine, Chungbuk National University, Gaeshin-dong, Cheongju 361-763, Korea
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Bodnar AL, Cortes-Burgos LA, Cook KK, Dinh DM, Groppi VE, Hajos M, Higdon NR, Hoffmann WE, Hurst RS, Myers JK, Rogers BN, Wall TM, Wolfe ML, Wong E. Discovery and structure-activity relationship of quinuclidine benzamides as agonists of alpha7 nicotinic acetylcholine receptors. J Med Chem 2005; 48:905-8. [PMID: 15715459 DOI: 10.1021/jm049363q] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A library of benzamides was tested for alpha7 nicotinic acetylcholine receptor (nAChR) agonist activity using a chimeric receptor in a functional, cell-based, high-throughput assay. From this library, quinuclidine benzamides were found to have alpha7 nAChR agonist activity. The SAR diverged from the activity of this compound class verses the 5-HT(3) receptor, a structural homologue of the alpha7 nAChR. PNU-282987, the most potent compound from this series, was also shown to open native alpha7 nAChRs in cultured rat neurons and to reverse an amphetamine-induced gating deficit in rats.
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Affiliation(s)
- Alice L Bodnar
- Department of Neuroscience, Global Research and Development, Pfizer Inc., Groton, CT, USA
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23
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Barann M, Schmidt K, Göthert M, Urban BW, Bönisch H. Influence of sodium substitutes on 5-HT-mediated effects at mouse 5-HT3 receptors. Br J Pharmacol 2004; 142:501-8. [PMID: 15148263 PMCID: PMC1574959 DOI: 10.1038/sj.bjp.0705788] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Revised: 03/08/2004] [Accepted: 03/10/2004] [Indexed: 01/11/2023] Open
Abstract
1 The influence of sodium ion substitutes on the 5-hydroxytryptamine (5-HT)-induced flux of the organic cation [14C]guanidinium through the ion channel of the mouse 5-HT3 receptor and on the competition of 5-HT with the selective 5-HT3 receptor antagonist [3H]GR 65630 was studied, unless stated otherwise, in mouse neuroblastoma N1E-115 cells. 2 Under physiological conditions (135 mm sodium), 5-HT induced a concentration-dependent [14C]guanidinium influx with an EC50 (1.3 microm) similar to that in electrophysiological studies. 3 The stepwise replacement of sodium by increasing concentrations of the organic cation hydroxyethyl trimethylammonium (choline) concentration dependently caused both a rightward shift of the 5-HT concentration-response curve and an increase in the maximum effect of 5-HT. Complete replacement of sodium resulted in a 34-fold lower potency of 5-HT and an almost two times higher maximal response. A low potency of 5-HT in choline buffer was also observed in other 5-HT3 receptor-expressing rodent cell lines (NG 108-15 or NCB 20). 4 Replacement of Na+ by Li+ left the potency and maximal effects of 5-HT almost unchanged. Replacement by tris (hydroxymethyl) methylamine (Tris), tetramethylammonium (TMA) or N-methyl-d-glucamine (NMDG) caused an increase in maximal response to 5-HT similar to that caused by choline. The potency of 5-HT was only slightly reduced by Tris, to a high degree decreased by TMA (comparable to the decrease by choline), but not influenced by NMDG. 5 The potency of 5-HT in inhibiting [3H]GR65630 binding to intact cells was 35-fold lower when sodium was completely replaced by choline, but remained unchanged after replacement by NMDG. 6 The results are compatible with the suggestion that choline competes with 5-HT for the 5-HT3 receptor; the increase in maximal response may be partly due to a choline-mediated delay of the 5-HT-induced desensitization. For studies of 5-HT-evoked [14C]guanidinium flux through 5-HT3 receptor channels, NMDG appears to be an 'ideal' sodium substituent since it increases the signal-to-noise ratio without interfering with 5-HT binding.
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Affiliation(s)
- M Barann
- Institut für Pharmakologie und Toxikologie, Universität Bonn, Reuterstrasse 2b, Bonn D-53113, Germany.
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Nakayama H, Yamakuni H, Nakayama A, Maeda Y, Imazumi K, Matsuo M, Mutoh S. Diphenidol Has No Actual Broad Antiemetic Activity in Dogs and Ferrets. J Pharmacol Sci 2004; 96:301-6. [PMID: 15528840 DOI: 10.1254/jphs.fpj04035x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Previous studies showed that diphenidol was effective on emetogens-induced pica, eating of non-nutritive substances, in rats, a model analogous to emesis in other species. We evaluated the actual antiemetic activity of diphenidol against four emetic stimuli in the dog and ferret, animals that possess an emetic reflex. In dogs, emetic responses to apomorphine were significantly prevented by diphenidol (3.2 mg/kg, i.v.), whereas diphenidol (3.2 mg/kg, i.v. x 2) showed a weak inhibition to the vomiting evoked by cisplatin. In ferrets, diphenidol (10 mg/kg, i.p.) exhibited a weak antiemetic activity on the emesis induced by copper sulfate and had no activity on emesis by loperamide. On the other hand, CP-122,721, a NK1-receptor antagonist, significantly reduced the emetic episodes to all four stimuli. These results suggest that the prediction of antiemetic activity of compounds in animals lacking an emetic reflex does not always correspond with actual antiemetic activity.
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Affiliation(s)
- Hiroe Nakayama
- Department of Urology, Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., Osaka, Japan
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25
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Abstract
The light/dark test is based on the innate aversion of rodents to brightly illuminated areas and on the spontaneous exploratory behaviour of rodents in response to mild stressors, that is, novel environment and light. The test apparatus consists of a small dark safe compartment (one third) and a large illuminated aversive compartment (two thirds). The test was developed with male mice. The strain, weight and age may be crucial factors. The extent to which an anxiolytic compound can facilitate exploratory activity depends on the baseline level in the control group. Differences between the type and severity of external stressors might account for the variable results reported by different laboratories. The light/dark test may be useful to predict anxiolytic-like or anxiogenic-like activity in mice. Transitions have been reported to be an index of activity-exploration because of habituation over time, and the time spent in each compartment to be a reflection of aversion. Classic anxiolytics (benzodiazepines) as well as the newer anxiolytic-like compounds (e.g. serotonergic drugs or drugs acting on neuropeptide receptors) can be detected using this paradigm. It has the advantages of being quick and easy to use, without requiring the prior training of animals.
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Affiliation(s)
- Michel Bourin
- Faculty of Medicine, EA 3256 Neurobiologie de l'Anxiété et de la Dépression, Faculté de Médecine BP 53508, 44035 Nantes Cedex 1, France.
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26
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Olivier B, Broersen LM, Slangen JL. 5-HT3 receptor ligands lack discriminative stimulus properties. Prog Neuropsychopharmacol Biol Psychiatry 2002; 26:463-71. [PMID: 11999896 DOI: 10.1016/s0278-5846(01)00290-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The putative discriminative stimulus of the 5-HT3 receptor antagonists ondansetron and (DL)-11-[(2-methyl-1H-imidazol-1-yl)methyl]-4,5,6,7,10,11,12-octahydroazepinol[3,2,1-jk]-carbazol-12-one hydrochloride (DU122932), and of the 5-HT3 receptor agonists 2-methyl-5-HT and 3,4-dichlorophenylbiguanide (3,4DCPB) were investigated in a standard two-lever, food-reinforced drug-saline discrimination procedure with groups of rats (N= 10 per group). In three groups of rats after 80 sessions with training doses ranging from 0.1 to 4.0 mg/kg po, stimulus control by ondansetron, DU122932 and 2-methyl-5-HT was still absent. The same 30 animals thereafter rapidly learned to discriminate chlordiazepoxide (CDP) from vehicle. In three other groups of rats, stimulus control by CDP was first established. Then, the vehicle was gradually (from 0.1 to 2.0 mg/kg po) replaced by either ondansetron, DU122932 or 2-methyl-5-HT. Finally, the dose of CDP was gradually decreased. In all three groups, stimulus control disappeared. A seventh group was trained to discriminate 3,4DCPB (5.0 mg/kg po) from saline. When training was not successful, dose and route were changed but discrimination was not attained. It is concluded that in the rat, using the classical two lever discrimination procedure, the 5-HT3 receptor ligands ondansetron, DU122932, 2-methyl-5-HT and 3,4DCPB are incapable of producing an internal state that can act as a stimulus to control responding.
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Affiliation(s)
- Berend Olivier
- Department of Psychopharmacology, Faculty of Pharmacy, Utrecht University, Utrecht, The Netherlands.
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27
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Baglin I, Daveu C, Lancelot JC, Bureau R, Dauphin F, Pfeiffer B, Renard P, Delagrange P, Rault S. First tricyclic oximino derivatives as 5-HT3 ligands. Bioorg Med Chem Lett 2001; 11:453-7. [PMID: 11229746 DOI: 10.1016/s0960-894x(00)00691-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The design and synthesis of a new type of 5-HT3 ligand with subnanomolar affinity are described. The O-dialkylaminoethyloximinothienopyrrolizine structure was deduced from molecular modeling studies by replacement of an amidine moiety by an oximino one.
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Affiliation(s)
- I Baglin
- Centre d'Etudes et de Recherche sur le Médicament de Normandie, Université de Caen, France
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28
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Abstract
1. The light/dark paradigm is based on the innate aversion of rodents to brightly illuminated areas and on the spontaneous exploratory behaviour of the animals, applying mild stressors i.e. novel environment and light. The test apparatus consists of a small dark secure compartment (one third) and a large illuminated aversive compartment (two thirds). 2. The test was developed with male mice. The strain, weight and age may be crucial factors. 3. The extent to which an anxiolytic compound can facilitate the exploratory activity depends on the baseline level in the control group. Differences between the type and severity of external stressors might account for variable results reported by different laboratories. 4. In conclusion, the black and white test may be useful to predict anxiolytic-like or anxiogenic-like activity in mice. Transitions have been reported to be an index of activity-exploration because of habituation over time and the time spent in each compartment to be a reflection of aversion. Classic anxiolytics (benzodiazepines) as well as the newer anxiolytic-like compounds (e.g. serotonergic drugs) can be detected using this paradigm. It has the advantages of being quick and easy to use, without requiring the prior training of animals.
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Affiliation(s)
- M Hascoët
- Faculty of Medicine, JE 2029 Neurobiologie de l'anxiété, Faculty de Médecine, Nantes, France
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29
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Abstract
Serotonin (5-hydroxytryptamine, 5-HT) mediates a wide variety of physiological functions by activating multiple receptors, and abnormalities of these receptor systems has been implicated in many psychiatric disorders including anxiety, depression, psychosis, migraine, disorders of sexual functioning, sleep, cognition, and feeding. Many of the currently used treatments for these disorders act by affecting the serotonergic system. Observation of serotonin receptor alterations, before and following effective treatments, may yield important insights into the aetiology of these psychiatric disorders and may ultimately lead to more selective and effective therapies. Copyright 2000 John Wiley & Sons, Ltd.
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Affiliation(s)
- Marie Naughton
- Department of Pharmacology, National University of Ireland, Galway, Ireland
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30
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Fida R, Bywater RA, Lyster DJ, Taylor GS. Chronotropic action of 5-hydroxytryptamine (5-HT) on colonic migrating motor complexes (CMMCs) in the isolated mouse colon. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 2000; 80:52-63. [PMID: 10742540 DOI: 10.1016/s0165-1838(00)00074-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effects of 5-hydroxytryptamine (5-HT) and related drugs on colonic migrating motor complexes (CMMCs) were evaluated in isolated colons from the heterozygotes of pie-bald lethal mice. 5-HT produced a dose-related increase in the frequency of CMMCs without any change in the amplitude or duration of the CMMC contractions themselves. The 5-HT(2) agonist, alpha-methyl 5-HT, (100 nM-1 microM) increased the frequency of CMMCs whilst the 5-HT(3) agonist, 2-methyl 5-HT, did so at 10 microM. The 5-HT(4) agonist, 5-methoxy dimethyl tryptamine oxalate did not alter the frequency of CMMCs in the concentration range 1 nM-10 microM. The 5-HT(3) receptor antagonist, ondansetron, increased the interval between CMMCs in the concentration range 100 nM-1 microM, whilst the 5-HT(1) receptor antagonist, methiothepin, the 5-HT(2) receptor antagonist, cyproheptadine and the 5-HT(4) receptor antagonist, SDZ 205 557, had no significant effects on the interval between CMMCs in the concentration range 1 nM-10 microM. The effects of 5-HT did not appear to be altered by the presence of ondansetron (1 microM) or cyproheptadine (1 microM). However, in the presence of ondansetron (1 microM), the further addition of cyproheptadine (1 microM) effectively abolished CMMCs. Furthermore, in the combined presence of these antagonists the effects of 5-HT were severely diminished. It is suggested that the frequency of CMMCs may be under the influence of endogenously released 5-HT in this preparation
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Affiliation(s)
- R Fida
- Department of Physiology, Monash University, Clayton, Australia.
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31
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Barann M, Dilger JP, Bönisch H, Göthert M, Dybek A, Urban BW. Inhibition of 5-HT3 receptors by propofol: equilibrium and kinetic measurements. Neuropharmacology 2000; 39:1064-74. [PMID: 10727717 DOI: 10.1016/s0028-3908(99)00205-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Patch-clamp/rapid solution exchange experiments as well as tracer ([14C]-guanidinium) influx measurements were applied to investigate effects of propofol on 5-HT3 receptor channels and compare the results with those obtained with pentobarbital. Currents induced by 30 microM 5-HT were recorded in outside-out patches from N1E-115 cells. Application of propofol 45 s before and during 5-HT application inhibited peak-currents and integrated current responses in a concentration-dependent manner (IC50 values=14.5 and 10.5 microM; Hill coefficients -1.5 and -1.3, respectively). The inhibitory effect of propofol in the current measurements was similar to the propofol-induced inhibition in tracer influx experiments in whole N1E-115 cells (Barann et al., 1993. Naunyn-Schmiedeberg's Archives of Pharmacology 347, 125-132). Pentobarbital-induced inhibition of 5-HT3 receptors in both patch-clamp (Barann et al., 1997. Neuropharmacology 36, 655-664) and tracer influx measurements indicated a lower potency and lower slope (IC50 values=130 and 55 microM; Hill coefficients -0.8 and -0.7, respectively) compared to propofol. Propofol, in contrast to pentobarbital, showed nearly the full potency when applied to the patches exclusively 45 s before 5-HT. Propofol was least effective when administered exclusively during 5-HT. The onset of inhibition of 5-HT-induced peak currents by propofol had a time constant of 220 ms, similar to the kinetics of 5-HT-induced desensitization.
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Affiliation(s)
- M Barann
- Klinik für Anästhesiologie und spezielle Intensivmedizin, Universitätskliniken Bonn, Sigmund-Freud Strasse 25, D-53105, Bonn, Germany.
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32
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Michelson D, Fava M, Amsterdam J, Apter J, Londborg P, Tamura R, Tepner RG. Interruption of selective serotonin reuptake inhibitor treatment. Double-blind, placebo-controlled trial. Br J Psychiatry 2000; 176:363-8. [PMID: 10827885 DOI: 10.1192/bjp.176.4.363] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND Abrupt interruption of therapy with selective serotonin reuptake inhibitors (SSRIs) has been associated with somatic and psychological symptoms. AIMS Systematically to assess symptoms and effects on daily functioning related to interruption of SSRI therapy. METHOD Patients treated with fluoxetine, setraline or paroxetine underwent identical five-day periods of treatment interruption and continued active treatment under double-blind, order-randomised conditions, with regular assessment of new symptoms. RESULTS Placebo substitution for paroxetine was associated with increases in the number and severity of adverse events following the second missed dose, and increases in functional impairment at five days. Placebo substitution for sertraline resulted in less pronounced changes, while interruption of fluoxetine was not associated with any significant increase in symptomatology. CONCLUSIONS Abrupt interruption of SSRI treatment can result in a syndrome characterised by specific physical and psychological symptoms. Incidence, timing and severity of symptoms vary among SSRIs in a fashion that appears to be related to plasma elimination characteristics.
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Affiliation(s)
- D Michelson
- Lilly Research Laboratories, Indianapolis, IN 46285, USA.
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33
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Olivier B, van Wijngaarden I, Soudijn W. 5-HT(3) receptor antagonists and anxiety; a preclinical and clinical review. Eur Neuropsychopharmacol 2000; 10:77-95. [PMID: 10706989 DOI: 10.1016/s0924-977x(99)00065-6] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The present paper reviews the evidence for anxiolytic activity of 5-HT(3) receptor antagonists in animal models of anxiety and in clinical trials in humans. Compared to the established anxiolytics (benzodiazepine receptor agonists and, to a lesser extent, 5-HT(1A) receptor agonists) 5-HT(3) receptor antagonists display a different anxiolytic profile. They are anxiolytic in a limited number of animal anxiety models. If active, they often are very potent and display bell-shaped dose response curves, whereas the ratio between therapeutic activity and side effects appears remarkably large. 5-HT(3) receptor antagonists remain active after chronic dosing and no indications for tolerance, dependence or rebound effects were found, which seems to make these drugs an attractive alternative to the benzodiazepines. However, the large body of animal data indicating a complete lack of psychotropic activity of 5-HT(3) receptor antagonists weakens the prediction of anxiolytic activity in these drugs. Human data are also controversial; some investigators have reported positive effects in anxiety disorders (panic disorder, GAD), others did not. It can be concluded that 5-HT(3) receptor antagonists do not represent a breakthrough in the treatment of various anxiety disorders, as initially suggested.
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Affiliation(s)
- B Olivier
- Department of Psychopharmacology, Faculty of Pharmacy, Rudolf Magnus Institute for Neurosciences, University of Utrecht, Utrecht, The Netherlands
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34
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Abstract
Psychopharmacology is rapidly becoming an adjuvant treatment to traditional rehabilitation strategies for patients with stroke or brain injury because it helps to facilitate recovery in a time-efficient manner. Norepinephrine, dopamine, acetylcholine, and serotonin appear to play important roles in recovery from stroke or brain injury. Animal models have shown that blockade of these neurotransmitters inhibits recovery, whereas recovery is promoted by drugs that promote norepinephrine, dopamine, acetylcholine, and serotonin activity. Preliminary evidence from human trials supports these findings. Further study is needed, but expanded use of pharmacologic agents for stroke and brain-injured patients appears imminent.
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35
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Rudd JA, Qian YM, Tsui KKC, Jones RL. Non-prostanoid prostacyclin mimetics as neuronal stimulants in the rat: comparison of vagus nerve and NANC innervation of the colon. Br J Pharmacol 2000; 129:782-90. [PMID: 10683203 PMCID: PMC1571884 DOI: 10.1038/sj.bjp.0703090] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The spontaneous activity of the rat isolated colon is suppressed by prostacyclin analogues such as cicaprost (IC(50)=4.0 nM). Activation of prostanoid IP(1)-receptors located on NANC inhibitory neurones is involved. However, several non-prostanoids, which show medium to high IP(1) agonist potency on platelet and vascular preparations, exhibit very weak inhibitory activity on the colon. The aim of the study was to investigate this discrepancy. Firstly, we have demonstrated the very high depolarizing potency of cicaprost on the rat isolated vagus nerve (EC(50)=0.23 nM). Iloprost, taprostene and carbacyclin were 7.9, 66, and 81 fold less potent than cicaprost, indicating the presence of IP(1) as opposed to IP(2)-receptors. Three non-prostanoid prostacyclin mimetics, BMY 45778, BMY 42393 and ONO-1301, although much less potent than cicaprost (195, 990 and 1660 fold respectively), behaved as full agonists on the vagus nerve. On re-investigating the rat colon, we found that BMY 45778 (0.1 - 3 microM), BMY 42393 (3 microM) and ONO-1301 (3 microM) behaved as specific IP(1) partial agonists, but their actions required 30 - 60 min to reach steady-state and only slowly reversed on washing. This profile contrasted sharply with the rapid and readily reversible contractions elicited by a related non-prostanoid ONO-AP-324, which is an EP(3)-receptor agonist. The full versus partial agonism of the non-prostanoid prostacyclin mimetics may be explained by the markedly different IP(1) agonist sensitivities of the two rat neuronal preparations. However, the slow kinetics of the non-prostanoids on the NANC system of the colon remain unexplained, and must be taken into account when characterizing neuronal IP-receptors.
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Affiliation(s)
- John A Rudd
- Department of Pharmacology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, NT, Hong Kong S.A.R., China
| | - Yue-ming Qian
- Department of Pharmacology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, NT, Hong Kong S.A.R., China
| | - Kenneth K C Tsui
- Department of Pharmacology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, NT, Hong Kong S.A.R., China
| | - Robert L Jones
- Department of Pharmacology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, NT, Hong Kong S.A.R., China
- Author for correspondence:
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36
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López-Rodríguez ML, Benhamú B, Morcillo MJ, Tejada ID, Orensanz L, Alfaro MJ, Martín MI. Benzimidazole derivatives. 2. Synthesis and structure-activity relationships of new azabicyclic benzimidazole-4-carboxylic acid derivatives with affinity for serotoninergic 5-HT(3) receptors. J Med Chem 1999; 42:5020-8. [PMID: 10585211 DOI: 10.1021/jm991076c] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new series of azabicyclic benzimidazole-4-carboxamides 2-21 and -carboxylates 22-30 were synthesized and evaluated for binding affinity at serotoninergic 5-HT(3) and 5-HT(4) receptors in the CNS. Most of the synthesized compounds exhibited high or very high affinity for the 5-HT(3) binding site and low to no significant affinity for the 5-HT(4) receptor. SAR observations indicated that a halogen atom at the 6-position and a nitro group at the 7-position of the benzimidazole ring is the best substitution pattern for 5-HT(3) affinity and 5-HT(3)/5-HT(4) selectivity, as well as no substitution in this ring. (S)-(-)-N-(Quinuclidin-3-yl)benzimidazole-4-carboxamides 2, 8, and 14 bound at central 5-HT(3) sites with high affinity (K(i) = 2.6, 0. 13, and 1.7 nM, respectively) and excellent selectivity over serotonin 5-HT(4) and 5-HT(1A) receptors (K(i) > 1000-10000 nM). Furthermore, these new 5-HT(3) receptor ligands were pharmacologically characterized as potent and selective 5-HT(3) antagonists in the isolated guinea pig ileum (pA(2) = 9.6, 9.9, and 9.1, respectively).
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Affiliation(s)
- M L López-Rodríguez
- Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain
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37
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Abstract
The 5-HT(3) receptor is a ligand-gated ion channel widely distributed in the central and peripheral nervous systems. Many selective 5-HT(3) receptor antagonists have been developed; animal studies with such compounds suggested their potential therapeutic value in combating emesis and a wide range of CNS diseases including anxiety, schizophrenia, drug dependence and Alzheimer's disease. Their successful introduction as anti-emetics, with irritable bowel syndrome emerging as a further indication have partially fulfilled this initial promise. However, the CNS area has been less productive and, to date, no selective 5-HT(3) receptor antagonist has been approved for use in a CNS disease.
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38
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Ozaki A, Sukamoto T. Improvement of cisplatin-induced emesis and delayed gastric emptying by KB-R6933, a novel 5-HT3 receptor antagonist. GENERAL PHARMACOLOGY 1999; 33:283-8. [PMID: 10480662 DOI: 10.1016/s0306-3623(98)00286-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The effects of a novel 5-hydroxytryptamine3 (5-HT3) receptor antagonist, KB-R6933, 6-amino-5-chloro-1-isopropyl-2-(4-methyl-1-piperazinyl)-benzimidazole dimaleate, on emesis and delayed gastric emptying induced by cisplatin were assessed in experimental models. Prophylactic intravenous or oral treatment with KB-R6933 prolonged the latent period until the first emetic episode and decreased the number of emetic episodes induced by cisplatin in ferrets. KB-R6933 immediately inhibited the subsequent emesis when administered to the ferrets which exhibited established vomiting after administration of cisplatin. In rats treated with cisplatin, the gastric emptying rate was significantly reduced. KB-R6933 reversed the reduction of gastric emptying induced by cisplatin. These results suggest that KB-R6933 is an antiemetic agent, and could improve the cisplatin-induced delay of gastric emptying.
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Affiliation(s)
- A Ozaki
- Pharmaceuticals R&D Center, Kanebo, Ltd., Osaka, Japan.
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39
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40
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Cappelli A, Anzini M, Vomero S, Canullo L, Mennuni L, Makovec F, Doucet E, Hamon M, Menziani MC, De Benedetti PG, Bruni G, Romeo MR, Giorgi G, Donati A. Novel potent and selective central 5-HT3 receptor ligands provided with different intrinsic efficacy. 2. Molecular basis of the intrinsic efficacy of arylpiperazine derivatives at the central 5-HT3 receptors. J Med Chem 1999; 42:1556-75. [PMID: 10229626 DOI: 10.1021/jm981112s] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Novel 5-HT3 receptor ligands were designed and synthesized with the aim of obtaining deeper insight into the molecular basis of the intrinsic efficacy of arylpiperazines interacting with the central 5-HT3 receptor. The newly synthesized compounds and some previously published compounds belonging to the same class of heteroarylpiperazines were tested for their potential ability to displace [3H]granisetron from rat cortical membranes. These 5-HT3 receptor binding studies revealed subnanomolar affinity in several of the compounds under study. The most active ligands were quipazine derivatives bearing a phenyl group in the 4-position and various oxygenated alkyl side chains in the 3-position of the quinoline nucleus. Qualitative and theoretical quantitative structure-affinity relationship studies were carried out, and the interaction model for the 5-HT3 ligands related to quipazine with their receptor, proposed in part 1 of the present work, was updated to incorporate the latest data. The potential 5-HT3 agonist/antagonist activity of 12 selected compounds was assessed in vitro on the 5-HT3 receptor-dependent [14C]guanidinium uptake in NG 108-15 cells. Their intrinsic efficacy ranged from the 5-HT3 full agonist properties of compounds 7a and 8h, i to those of partial agonists 10a,d and antagonists 8b,d,e, and 9c, d,h,i. The comparison between these functional data and those relative to the previously described compounds suggested that in this class of 5-HT3 ligands the intrinsic efficacy is modulated in a rather subtle manner by the steric features of the heteroaryl moiety.
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Affiliation(s)
- A Cappelli
- Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Banchi di Sotto 55, 53100 Siena, Italy
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41
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Squires RF, Saederup E. Clozapine's antipsychotic effects do not depend on blockade of 5-HT3 receptors. Neurochem Res 1999; 24:659-67. [PMID: 10344595 DOI: 10.1023/a:1021052409140] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Sixteen known 5-HT3 receptor blockers, including clozapine, fully or partially reverse the inhibitory effect of 1 microM GABA on [35S]TBPS binding, indicating that they are also GABA(A) antagonists, some of them selective for subsets of GABA(A) receptors. The 5-HT3 receptor blocker, ondansetron, has been reported to produce some antipsychotic and anxiolytic effects. However, no antipsychotic effects have been reported for a large number of highly potent 5-HT3 receptor blockers. Like clozapine, ondansetron partially reverses the inhibitory effect of GABA on [35S]TBPS binding. Additivity experiments suggest that ten 5-HT3 receptor blockers tested at low concentrations preferentially block subtypes of GABA(A) receptors that are among those blocked by clozapine. Wiley and Porter (29) reported that MDL-72222, the most potent GABA(A) antagonist described here, partially generalizes (71%) with clozapine in rats trained to discriminate an interoceptive clozapine stimulus, but only at a dose that severely decreases responding. Tropisetron (ICS-205,930) exhibits both GABA-positive and GABA-negative effects. R-(+)-zacopride is 6-fold more potent than S-(-)-zacopride as a GABA(A) antagonist. We conclude that the observed antipsychotic and, possibly, anxiolytic effects of some 5-HT3 receptor blockers are due to selective antagonism of certain GABA(A) receptors, and not to blockade of 5-HT3 receptors. We speculate that the anxiolytic and sedative effects of clozapine and several other antipsychotic drugs may be due to selective blockade of alpha1beta2gamma2 GABA(A) receptors which are preferentially located on certain types of GABAergic interneurons (probably parvalbumin positive). Blockade of these receptors will increase the inhibitory output of these interneurons. So far, no highly potent GABA(A) antagonists with clozapine-like selectivity have been identified. Such compounds may exhibit improved clozapine-like antipsychotic activity.
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Affiliation(s)
- R F Squires
- The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY 10962, USA
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42
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Humphrey PP, Bountra C, Clayton N, Kozlowski K. Review article: the therapeutic potential of 5-HT3 receptor antagonists in the treatment of irritable bowel syndrome. Aliment Pharmacol Ther 1999. [PMID: 10429738 DOI: 10.1046/j.1365-2036.1999.00003.x-i2] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
There is evidence from studies, in both animals and humans, that 5-HT3 receptor blockade has potential value in the treatment of irritable bowel syndrome, particularly in those patients with diarrhoea-predominant bowel habits. New findings suggest that 5-HT3 receptors exist on gut afferent neurones and that their activation by locally released 5-HT leads to visceral nociceptive stimulation, in addition to increased neuronally-mediated motor and secretory activity. If this concept is validated, it will provide a rationale for the use of 5-HT3 receptor antagonists in patients with increased gut motility, reduced fluid absorption and low nociceptive thresholds leading to abdominal pain. Alosetron is a highly selective, potent 5-HT3 receptor antagonist which is well absorbed with a long pharmacodynamic half-life. Its ability to provide long-lasting blockade of 5-HT3 receptors throughout the body make it an ideal candidate within its class to evaluate the clinical hypothesis that sustained and ubiquitous 5-HT3 receptor blockade is of value in the treatment of IBS.
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Affiliation(s)
- P P Humphrey
- Glaxo Institute of Applied Pharmacology, Department of Pharmacology, University of Cambridge, UK.
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43
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Jørgensen H, Knigge U, Kjaer A, Warberg J. Adrenocorticotropic hormone secretion in rats induced by stimulation with serotonergic compounds. hsj@mfi.ku.dk. J Neuroendocrinol 1999; 11:283-90. [PMID: 10223282 DOI: 10.1046/j.1365-2826.1999.00328.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The serotonin receptors involved in the secretion of adrenocorticotropin hormone (ACTH) were investigated in conscious adult male rats. Administration of serotonin (5-HT), 5-hydroxytryptophan (5-HTP) in combination with the serotonin reuptake inhibitor fluoxetine (Flx), or of the 5-HT agonists 8-OH-DPAT (5-HT1A), 5-carboxamido-tryptamine (5-HT1A+1B+5A+7), RU 24969 (5-HT1B+1A), DOI (5-HT2A+2c), S-alpha-methyl-5-HT (5-HT2A+2B+2c), MK212 (5-HT2B+2c), or methyl-chlorophenyl-piperazine (5-HT2A+2c) dose-dependently stimulated ACTH secretion. The 5-HT3 agonist 2-methyl-5-HT had no effect. Administration of a 5-HT1 agonist in combination with any of the 5-HT2 agonists DOI, S-alpha-methyl-5-HT or MK212 had an additive effect on the plasma concentration of ACTH. The ACTH stimulating effect of each of the 5-HT agonists was inhibited by pretreatment with antagonists with corresponding 5-HT receptor affinity. The ACTH response to 5-HT or 5-HTP/Flx was inhibited by injection with the 5-HT1A+2A+2c+5A+7 antagonist methysergide, the 5-HT2A antagonist ketanserine and the 5-HT2C+2A antagonist LY 53857. The 5-HT1A antagonist WAY 100635 enhanced 5-HT- and 5-HTP/Flx-induced ACTH secretion, suggesting a presynaptic 5-HT1A autoreceptor effect of the drug. The 5-HT3 antagonist ondansetrone had no effect on the either of the 5-HT agonists. The 5-HT3+4 antagonist tropisetrone attenuated the effect of 5-HTP/Flx, which may suggest a stimulation of ACTH secretion via 5-HT4 receptors. It is concluded that 5-HT1A, 5-HT2A+2C, and to a lesser extent 5-HT1B receptors, but not 5-HT3 receptors are involved in the effects of serotonin agonists on ACTH secretion. Furthermore, an involvement of the 5-HT5A and the 5-HT7 receptor is possible.
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Affiliation(s)
- H Jørgensen
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, Denmark.
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44
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Monti JM, Ponzoni A, Jantos H, Lagos P, Silveira R, Banchero P. Effects of accumbens m-chlorophenylbiguanide microinjections on sleep and waking in intact and 6-hydroxydopamine-treated rats. Eur J Pharmacol 1999; 364:89-98. [PMID: 9932710 DOI: 10.1016/s0014-2999(98)00826-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Effects of the 5-HT3 receptor agonist, m-chlorophenylbiguanide (10.0-40.0 microg), on sleep and waking were studied in control, vehicle-treated and 6-hydroxydopamine-injected rats. Bilateral injections of m-chlorophenylbiguanide into the nucleus accumbens of the control and the vehicle-infused animals significantly increased waking and reduced slow wave sleep. Rapid eye movement sleep (REM sleep) remained unchanged. Pretreatment with the selective 5-HT3 receptor antagonist, MDL 72222 (1aH,3a,5a, H-tropan-3-yl-3,5-dichloro-benzoate) (0.5 mg/kg, s.c.), reversed the effects of m-chlorophenylbiguanide (10.0-20.0 microg) on sleep and waking in the control group. Administration of the 5-HT3 receptor agonist to the 6-hydroxydopamine-treated animals modified only slightly the time spent in wakefulness and slow wave sleep, while REM sleep was significantly and dose dependently reduced. Our findings further support the proposal that increase of wakefulness and reduction of slow wave sleep after activation of 5-HT3 receptors, is partly related to the release of endogenous dopamine.
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Affiliation(s)
- J M Monti
- Department of Pharmacology and Therapeutics, School of Medicine, Clinics Hospital, Montevideo, Uruguay.
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45
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Masjedizadeh MR, Parnes H. Synthesis of tritium labelled (R) and (S)-3-aminoquinuclidine: A ubiquitous component of serotonin receptor ligands, part I. J Labelled Comp Radiopharm 1998. [DOI: 10.1002/(sici)1099-1344(199601)38:1<41::aid-jlcr811>3.0.co;2-n] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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46
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Gui XY. Mast cells: a possible link between psychological stress, enteric infection, food allergy and gut hypersensitivity in the irritable bowel syndrome. J Gastroenterol Hepatol 1998; 13:980-9. [PMID: 9835312 DOI: 10.1111/j.1440-1746.1998.tb00558.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Intestinal mast cell activation (degranulation), which results from previous enteric infection and/or intestinal allergy, may play a central role in the gut hypersensitivity in both motor response and visceral perception in the Irritable Bowel syndrome. This occurs through various mediators acting on enteric neurons and smooth muscle cells. Psychological stress may trigger this sensitive alarm system via the brain-gut axis.
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Affiliation(s)
- X Y Gui
- University of Sydney Department of Medicine, Royal North Shore Hospital, St Leonards, New South Wales, Australia
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47
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Quantitative evaluation of 5-hydroxytryptamine (serotonin) neuronal release and uptake: an investigation of extrasynaptic transmission. J Neurosci 1998. [PMID: 9634551 DOI: 10.1523/jneurosci.18-13-04854.1998] [Citation(s) in RCA: 207] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Whether neurotransmitters are restricted to the synaptic cleft (participating only in hard-wired neurotransmission) or diffuse to remote receptor sites (participating in what has been termed volume or paracrine transmission) depends on a number of factors. These include (1) the location of release sites with respect to the receptors, (2) the number of molecules released, (3) the diffusional rate away from the release site, determined by both the geometry near the release site as well as binding interactions, and (4) the removal of transmitter by the relevant transporter. Fast-scan cyclic voltammetry allows for the detection of extrasynaptic concentrations of many biogenic amines, permitting direct access to many of these parameters. In this study the hypothesis that 5-hydroxytryptamine (5-HT) transmission is primarily extrasynaptic in the substantia nigra reticulata, a terminal region with identified synaptic contacts, and the dorsal raphe nucleus, a somatodendritic region with rare synaptic incidence, was tested in brain slices prepared from the rat. Using carbon fiber microelectrodes, we found the concentration of 5-HT released per stimulus pulse in both regions to be identical when elicited by single pulse stimulations or trains at high frequency. 5-HT efflux elicited by a single stimulus pulse was unaffected by uptake inhibition or receptor antagonism. Thus, synaptic efflux is not restricted by binding to intrasynaptic receptors or transporters. The number of 5-HT molecules released per terminal was estimated in the substantia nigra reticulata and was considerably less than the number of 5-HT transporter and receptor sites, reinforcing the hypothesis that these sites are extrasynaptic. Furthermore, the detected extrasynaptic concentrations closely match the affinity for the predominant 5-HT receptor in each region. Although they do not disprove the existence of classical synaptic transmission, our results support the existence of paracrine neurotransmission in both serotonergic regions.
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Hammas B, Hvarfner A, Thörn SE, Wattwil M. Effects of propofol on ipecacuanha-induced nausea and vomiting. Acta Anaesthesiol Scand 1998; 42:447-51. [PMID: 9563865 DOI: 10.1111/j.1399-6576.1998.tb05140.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND The purpose of this study was to evaluate if propofol has 5-HT3 antagonistic effects. Ipecacuanha is known to release serotonin (5-HT) in the gastrointestinal tract and therefore ipecacuanha syrup was used to induce nausea and vomiting. The 5-HT3 antagonist ondansetron was used as a control substance. METHOD Ten healthy male volunteers (20-37 years) were studied on three occasions and were randomly allocated to receive a concomitant infusion of propofol (initial bolus 0.1 mg kg(-1) then 1 mg kg(-1)h(-1)), ondansetron (initial bolus 0.11 mg kg(-1) then 14 microg kg(-1)h(-1)) and placebo on either occasion. The infusions started 30 min before oral ingestion of 30 ml of ipecacuanha and continued until 150 min after the intake. The number of retchings was recorded and the intensity of nausea was estimated by the subjects on a visual analog scale. RESULTS During the first 150 min after ingestion of ipecacuanha there were no retchings during the ondansetron infusion (P=0.01 vs placebo, P=0.02 vs propofol) and significantly fewer retchings during propofol infusion compared to placebo (P<0.02). There was no nausea during the ondansetron infusion (P<0.01 vs placebo and propofol) but the volunteers experienced nausea both during the placebo and propofol infusion (NS). CONCLUSION This study in volunteers has shown that propofol reduces the intensity of retching after oral intake of ipecacuanha syrup. As ipecacuanha releases 5-hydroxytryptamine, it can be concluded that propofol may have a weak 5-HT3 antagonistic effect.
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Affiliation(s)
- B Hammas
- Department of Anesthesiology and Intensive Care, Orebro Medical Center Hospital, Sweden
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49
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Cappelli A, Anzini M, Vomero S, Mennuni L, Makovec F, Doucet E, Hamon M, Bruni G, Romeo MR, Menziani MC, De Benedetti PG, Langer T. Novel potent and selective central 5-HT3 receptor ligands provided with different intrinsic efficacy. 1. Mapping the central 5-HT3 receptor binding site by arylpiperazine derivatives. J Med Chem 1998; 41:728-41. [PMID: 9513601 DOI: 10.1021/jm970645i] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Synthesis and pharmacological evaluation of a series of condensed quinoline and pyridine derivatives bearing a N-methylpiperazine moiety attached to the 2-position of the quinoline or pyridine nucleus are described. 5-HT receptor binding studies revealed subnanomolar affinity for the 5-HT3 receptor subtype in some of the compounds under study. The most active compound (5b) displayed a Ki value about 1 order of magnitude higher than that of quipazine along with a higher selectivity. The potential 5-HT3 agonist/antagonist activity of four selected compounds was assessed in vitro on 5-HT3 receptor-dependent [14C]guanidinium uptake in NG 108-15 cells. Compound 5j acted as a 5-HT3 agonist in this assay with an EC50 value close to that reported for quipazine, while 5b was a partial agonist with an EC50 value of about 0.25 nM, and compound 5c possessed antagonist properties with an IC50 value (approximately 8 nM) in the same range as those of previously characterized 5-HT3 receptor antagonists. Qualitative and quantitative structure-affinity relationship studies carried out by making use of theoretical molecular descriptors allowed to elucidate the role of the main pharmacophoric components and to develop a model for the interaction of the 5-HT3 ligands related to quipazine with their receptor.
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Affiliation(s)
- A Cappelli
- Dipartimento Farmaco Chimico Technologico, Università di Siena, Italy
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50
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López-Rodríguez ML, Morcillo MJ, Benhamú B, Rosado ML. Comparative receptor mapping of serotoninergic 5-HT3 and 5-HT4 binding sites. J Comput Aided Mol Des 1997; 11:589-99. [PMID: 9491351 DOI: 10.1023/a:1007908707650] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The clinical use of currently available drugs acting at the 5-HT4 receptor has been hampered by their lack of selectivity over 5-HT3 binding sites. For this reason, there is considerable interest in the medicinal chemistry of these serotonin receptor subtypes, and significant effort has been made towards the discovery of potent and selective ligands. Computer-aided conformational analysis was used to characterize serotoninergic 5-HT3 and 5-HT4 receptor recognition. On the basis of the generally accepted model of the 5-HT3 antagonist pharmacophore, we have performed a receptor mapping of this receptor binding site, following the active analog approach (AAA) defined by Marshall. The receptor excluded volume was calculated as the union of the van der Waals density maps of nine active ligands (pKi > or = 8.9), superimposed in pharmacophoric conformations. Six inactive analogs (pKi < 7.0) were subsequently used to define the essential volume, which in its turn can be used to define the regions of steric intolerance of the 5-HT3 receptor. Five active ligands (pKi > or = 9.3) at 5-HT4 receptors were used to construct an antagonist pharmacophore for this receptor, and to determine its excluded volume by superimposition of pharmacophoric conformations. The volume defined by the superimposition of five inactive 5-HT4 receptor analogs that possess the pharmacophoric elements (pKi < or = 6.6) did not exceed the excluded volume calculated for this receptor. In this case, the inactivity may be due to the lack of positive interaction of the amino moiety with a hypothetical hydrophobic pocket, which would interact with the voluminous substituents of the basic nitrogen of active ligands. The difference between the excluded volumes of both receptors has confirmed that the main difference is indeed in the basic moiety. Thus, the 5-HT3 receptor can only accommodate small substituents in the position of the nitrogen atom, whereas the 5-HT4 receptor requires more voluminous groups. Also, the basic nitrogen is located at ca. 8.0 A from the aromatic moiety in the 5-HT4 antagonist pharmacophore, whereas this distance is ca. 7.5 A in the 5-HT3 antagonist model. The comparative mapping of both serotoninergic receptors has allowed us to confirm the three-component pharmacophore accepted for the 5-HT3 receptor, as well as to propose a steric model for the 5-HT4 receptor binding site. This study offers structural insights to aid the design of new selective ligands, and the resulting models have received some support from the synthesis of two new active and selective ligands: 24 (Ki(5-HT3) = 3.7 nM; Ki(5-HT4) > 1000 nM) and 25 (Ki(5-HT4) = 13.7 nM; Ki(5-HT3) > 10,000 nM).
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Affiliation(s)
- M L López-Rodríguez
- Departamento de Química Orgánica I, Facultad de Ciencias, Químicas, Universidad Complutense, Madrid, Spain
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