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Maksimovic S, Useinovic N, Quillinan N, Covey DF, Todorovic SM, Jevtovic-Todorovic V. General Anesthesia and the Young Brain: The Importance of Novel Strategies with Alternate Mechanisms of Action. Int J Mol Sci 2022; 23:ijms23031889. [PMID: 35163810 PMCID: PMC8836828 DOI: 10.3390/ijms23031889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 02/04/2022] [Accepted: 02/05/2022] [Indexed: 12/10/2022] Open
Abstract
Over the past three decades, we have been grappling with rapidly accumulating evidence that general anesthetics (GAs) may not be as innocuous for the young brain as we previously believed. The growing realization comes from hundreds of animal studies in numerous species, from nematodes to higher mammals. These studies argue that early exposure to commonly used GAs causes widespread apoptotic neurodegeneration in brain regions critical to cognition and socio-emotional development, kills a substantial number of neurons in the young brain, and, importantly, results in lasting disturbances in neuronal synaptic communication within the remaining neuronal networks. Notably, these outcomes are often associated with long-term impairments in multiple cognitive-affective domains. Not only do preclinical studies clearly demonstrate GA-induced neurotoxicity when the exposures occur in early life, but there is a growing body of clinical literature reporting similar cognitive-affective abnormalities in young children who require GAs. The need to consider alternative GAs led us to focus on synthetic neuroactive steroid analogues that have emerged as effective hypnotics, and analgesics that are apparently devoid of neurotoxic effects and long-term cognitive impairments. This would suggest that certain steroid analogues with different cellular targets and mechanisms of action may be safe alternatives to currently used GAs. Herein we summarize our current knowledge of neuroactive steroids as promising novel GAs.
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Affiliation(s)
- Stefan Maksimovic
- Department of Anesthesiology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA; (N.U.); (N.Q.); (S.M.T.); (V.J.-T.)
- Correspondence:
| | - Nemanja Useinovic
- Department of Anesthesiology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA; (N.U.); (N.Q.); (S.M.T.); (V.J.-T.)
| | - Nidia Quillinan
- Department of Anesthesiology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA; (N.U.); (N.Q.); (S.M.T.); (V.J.-T.)
- Neuronal Injury and Plasticity Program, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA
| | - Douglas F. Covey
- Department of Developmental Biology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA;
- Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Slobodan M. Todorovic
- Department of Anesthesiology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA; (N.U.); (N.Q.); (S.M.T.); (V.J.-T.)
| | - Vesna Jevtovic-Todorovic
- Department of Anesthesiology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA; (N.U.); (N.Q.); (S.M.T.); (V.J.-T.)
- Department of Pharmacology, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA
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Manzella FM, Covey DF, Jevtovic-Todorovic V, Todorovic SM. Synthetic neuroactive steroids as new sedatives and anaesthetics: Back to the future. J Neuroendocrinol 2022; 34:e13086. [PMID: 35014105 PMCID: PMC8866223 DOI: 10.1111/jne.13086] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 12/03/2021] [Accepted: 12/22/2021] [Indexed: 02/03/2023]
Abstract
Since the 1990s, there has been waning interest in researching general anaesthetics (anaesthetics). Although currently used anaesthetics are mostly safe and effective, they are not without fault. In paediatric populations and neonatal animal models, they are associated with learning impairments and neurotoxicity. In an effort to research safer anaesthetics, we have gone back to re-examine neuroactive steroids as anaesthetics. Neuroactive steroids are steroids that have direct, local effects in the central nervous system. Since the discovery of their anaesthetic effects, neuroactive steroids have been consistently used in human or veterinary clinics as preferred anaesthetic agents. Although briefly abandoned for clinical use due to unwanted vehicle side effects, there has since been renewed interest in their therapeutic value. Neuroactive steroids are safe sedative/hypnotic and anaesthetic agents across various animal species. Importantly, unlike traditional anaesthetics, they do not cause extensive neurotoxicity in the developing rodent brain. Similar to traditional anaesthetics, neuroactive steroids are modulators of synaptic and extrasynaptic γ-aminobutyric acid type A (GABAA ) receptors and their interactions at the GABAA receptor are stereo- and enantioselective. Recent work has also shown that these agents act on other ion channels, such as high- and low-voltage-activated calcium channels. Through these mechanisms of action, neuroactive steroids modulate neuronal excitability, which results in characteristic burst suppression of the electroencephalogram, and a surgical plane of anaesthesia. However, in addition to their interactions with voltage and ligand gated ions channels, neuroactive steroids interact with membrane bound metabotropic receptors and xenobiotic receptors to facilitate signaling of prosurvival, antiapoptotic pathways. These pathways play a role in their neuroprotective effects in neuronal injury and may also prevent extensive apoptosis in the developing brain during anaesthesia. The current review explores the history of neuroactive steroids as anaesthetics in humans and animal models, their diverse mechanisms of action, and their neuroprotective properties.
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Affiliation(s)
- Francesca M Manzella
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Douglas F Covey
- Department of Developmental Biology, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
- Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
| | - Vesna Jevtovic-Todorovic
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Slobodan M Todorovic
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
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Joksimovic SL, Donald RR, Park JY, Todorovic SM. Inhibition of multiple voltage-gated calcium channels may contribute to spinally mediated analgesia by epipregnanolone in a rat model of surgical paw incision. Channels (Austin) 2019; 13:48-61. [PMID: 30672394 PMCID: PMC6380214 DOI: 10.1080/19336950.2018.1564420] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Voltage-activated calcium channels play an important role in excitability of sensory nociceptive neurons in acute and chronic pain models. We have previously shown that low-voltage-activated calcium channels, or T-type channels (T-channels), increase excitability of sensory neurons after surgical incision in rats. We have also found that endogenous 5β-reduced neuroactive steroid epipregnanolone [(3β,5β)-3-hydroxypregnan-20-one] blocked isolated T-currents in dorsal root ganglion (DRG) cells in vitro, and reduced nociceptive behavior in vivo, after local intraplantar application into the foot pads of heathy rats and mice. Here, we investigated if epipregnanolone exerts an antinociceptive effect after intrathecal (i.t.) application in healthy rats, as well as an antihyperalgesic effect in a postsurgical pain model. We also studied if this endogenous neurosteroid blocks currents originating from high voltage-activated (HVA) calcium channels in rat sensory neurons. In in vivo studies, we found that epipregnanolone alleviated thermal and mechanical nociception in healthy rats after i.t. administration without affecting their sensory-motor abilities. Furthermore, epipregnanolone effectively reduced mechanical hyperalgesia after i.t application in rats after surgery. In subsequent in vitro studies, we found that epipregnanolone blocked isolated HVA currents in nociceptive sensory neurons with an IC50 of 3.3 μM in a G-protein-dependent fashion. We conclude that neurosteroids that have combined inhibitory effects on T-type and HVA calcium currents may be suitable for development of novel pain therapies during the perioperative period.
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Affiliation(s)
- Sonja Lj Joksimovic
- a Department of Anesthesiology , University of Colorado Denver , Aurora , CO , USA
| | - Rebecca R Donald
- b Department of Anesthesiology , Duke University Medical School , Durham , NC , USA
| | - Ji-Yong Park
- c Department of Anesthesiology and Pain Medicine, College of Medicine , Korea University , Seoul , Republic of Korea
| | - Slobodan M Todorovic
- a Department of Anesthesiology , University of Colorado Denver , Aurora , CO , USA.,d Neuroscience Graduate Program , University of Colorado Denver , Aurora , CO , USA
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Lau C, Thakre PP, Bellingham MC. Alfaxalone Causes Reduction of Glycinergic IPSCs, but Not Glutamatergic EPSCs, and Activates a Depolarizing Current in Rat Hypoglossal Motor Neurons. Front Cell Neurosci 2019; 13:100. [PMID: 30967762 PMCID: PMC6440435 DOI: 10.3389/fncel.2019.00100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 02/27/2019] [Indexed: 11/20/2022] Open
Abstract
We investigated effects of the neuroactive steroid anesthetic alfaxalone on intrinsic excitability, and on inhibitory and excitatory synaptic transmission to hypoglossal motor neurons (HMNs). Whole cell recordings were made from HMNs in brainstem slices from 7 to 14-day-old Wistar rats. Spontaneous, miniature, and evoked inhibitory post-synaptic currents (IPSCs), and spontaneous and evoked excitatory PSCs (EPSCs) were recorded at –60 mV. Alfaxalone did not alter spontaneous glycinergic IPSC peak amplitude, rise-time or half-width up to 10 μM, but reduced IPSC frequency from 3 μM. Evoked IPSC amplitude was reduced from 30 nM. Evoked IPSC rise-time was prolonged and evoked IPSC decay time was increased only by 10 μM alfaxalone. Alfaxalone also decreased evoked IPSC paired pulse ratio (PPR). Spontaneous glutamatergic EPSC amplitude and frequency were not altered by alfaxalone, and evoked EPSC amplitude and PPR was also unchanged. Alfaxalone did not alter HMN repetitive firing or action potential amplitude. Baseline holding current at −60 mV with a CsCl-based pipette solution was increased in an inward direction; this effect was not seen when tetrodotoxin (TTX) was present. These results suggest that alfaxalone modulates glycine receptors (GlyRs), causing a delayed and prolonged channel opening, as well as causing presynaptic reduction of glycine release, and activates a membrane current, which remains to be identified. Alfaxalone selectively reduces glycinergic inhibitory transmission to rat HMNs via a combination of pre- and post-synaptic mechanisms. The net effect of these responses to alfaxalone is to increase HMN excitability and may therefore underlie neuro-motor excitation during neurosteroid anesthesia.
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Affiliation(s)
- Cora Lau
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Prajwal P Thakre
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Mark C Bellingham
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
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Schneider T, Dibué M, Hescheler J. How "Pharmacoresistant" is Cav2.3, the Major Component of Voltage-Gated R-type Ca2+ Channels? Pharmaceuticals (Basel) 2013; 6:759-76. [PMID: 24276260 PMCID: PMC3816731 DOI: 10.3390/ph6060759] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/26/2013] [Accepted: 05/06/2013] [Indexed: 12/04/2022] Open
Abstract
Membrane-bound voltage-gated Ca2+ channels (VGCCs) are targets for specific signaling complexes, which regulate important processes like gene expression, neurotransmitter release and neuronal excitability. It is becoming increasingly evident that the so called “resistant” (R-type) VGCC Cav2.3 is critical in several physiologic and pathophysiologic processes in the central nervous system, vascular system and in endocrine systems. However its eponymous attribute of pharmacologic inertness initially made in depth investigation of the channel difficult. Although the identification of SNX-482 as a fairly specific inhibitor of Cav2.3 in the nanomolar range has enabled insights into the channels properties, availability of other pharmacologic modulators of Cav2.3 with different chemical, physical and biological properties are of great importance for future investigations. Therefore the literature was screened systematically for molecules that modulate Cav2.3 VGCCs.
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Affiliation(s)
- Toni Schneider
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
- Authors to whom correspondence should be addressed; E-Mails: (T.S.); (M.D.); Tel.: +49-221-478-69446 (T.S.); Fax: +49-221-478-6965 (T.S.)
| | - Maxine Dibué
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, Duesseldorf D-40225, Germany & Center of Molecular Medicine, Cologne D-50931, Germany
- Authors to whom correspondence should be addressed; E-Mails: (T.S.); (M.D.); Tel.: +49-221-478-69446 (T.S.); Fax: +49-221-478-6965 (T.S.)
| | - Jürgen Hescheler
- Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, Cologne D-50931, Germany; E-Mail:
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Piekarz AD, Due MR, Khanna M, Wang B, Ripsch MS, Wang R, Meroueh SO, Vasko MR, White FA, Khanna R. CRMP-2 peptide mediated decrease of high and low voltage-activated calcium channels, attenuation of nociceptor excitability, and anti-nociception in a model of AIDS therapy-induced painful peripheral neuropathy. Mol Pain 2012; 8:54. [PMID: 22828369 PMCID: PMC3502107 DOI: 10.1186/1744-8069-8-54] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 07/02/2012] [Indexed: 11/10/2022] Open
Abstract
Background The ubiquity of protein-protein interactions in biological signaling offers ample opportunities for therapeutic intervention. We previously identified a peptide, designated CBD3, that suppressed inflammatory and neuropathic behavioral hypersensitivity in rodents by inhibiting the ability of collapsin response mediator protein 2 (CRMP-2) to bind to N-type voltage-activated calcium channels (CaV2.2) [Brittain et al. Nature Medicine 17:822–829 (2011)]. Results and discussion Here, we utilized SPOTScan analysis to identify an optimized variation of the CBD3 peptide (CBD3A6K) that bound with greater affinity to Ca2+ channels. Molecular dynamics simulations demonstrated that the CBD3A6K peptide was more stable and less prone to the unfolding observed with the parent CBD3 peptide. This mutant peptide, conjugated to the cell penetrating motif of the HIV transduction domain protein TAT, exhibited greater anti-nociception in a rodent model of AIDS therapy-induced peripheral neuropathy when compared to the parent TAT-CBD3 peptide. Remarkably, intraperitoneal administration of TAT-CBD3A6K produced none of the minor side effects (i.e. tail kinking, body contortion) observed with the parent peptide. Interestingly, excitability of dissociated small diameter sensory neurons isolated from rats was also reduced by TAT-CBD3A6K peptide suggesting that suppression of excitability may be due to inhibition of T- and R-type Ca2+ channels. TAT-CBD3A6K had no effect on depolarization-evoked calcitonin gene related peptide (CGRP) release compared to vehicle control. Conclusions Collectively, these results establish TAT-CBD3A6K as a peptide therapeutic with greater efficacy in an AIDS therapy-induced model of peripheral neuropathy than its parent peptide, TAT-CBD3. Structural modifications of the CBD3 scaffold peptide may result in peptides with selectivity against a particular subset of voltage-gated calcium channels resulting in a multipharmacology of action on the target.
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Affiliation(s)
- Andrew D Piekarz
- Department of Pharmacology and Toxicology, 950 West Walnut Street, Indianapolis, IN 46202, USA
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Jevtovic-Todorovic V, Covey DF, Todorovic SM. Are neuroactive steroids promising therapeutic agents in the management of acute and chronic pain? Psychoneuroendocrinology 2009; 34 Suppl 1:S178-85. [PMID: 19577375 PMCID: PMC2795041 DOI: 10.1016/j.psyneuen.2009.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 04/28/2009] [Accepted: 06/02/2009] [Indexed: 10/20/2022]
Abstract
Neuroactive steroids with potentiating effects on GABA(A) channels and inhibitory effects on T-type Ca2+ channels which are located in peripheral sensory neurons are potent modulators of pain perception. The focus of this review is on peripheral anti-nociceptive properties of 5alpha- and 5beta-reduced neuroactive steroids with either selective or combined modulatory action on GABA(A) and T-type Ca2+ channel-mediated neurotransmission. We report that these neuroactive steroids are very effective in alleviating peripheral nociception in both acute and chronic pain conditions in animal models of pain. We believe that promising animal data warrant the exploration of their usefulness in clinical settings especially considering the fact that chronic pain sufferers are often young and otherwise healthy people.
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Affiliation(s)
- Vesna Jevtovic-Todorovic
- Department of Anesthesiology, University of Virginia Health System, PO Box 800710, Charlottesville, VA, USA.
| | - Douglas F. Covey
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Slobodan M. Todorovic
- Department of Anesthesiology, University of Virginia Health System, PO Box 800710, Charlottesville, VA
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Zheng P. Neuroactive steroid regulation of neurotransmitter release in the CNS: Action, mechanism and possible significance. Prog Neurobiol 2009; 89:134-52. [DOI: 10.1016/j.pneurobio.2009.07.001] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 03/11/2009] [Accepted: 07/02/2009] [Indexed: 12/31/2022]
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Covey DF. ent-Steroids: novel tools for studies of signaling pathways. Steroids 2009; 74:577-85. [PMID: 19103212 PMCID: PMC2668732 DOI: 10.1016/j.steroids.2008.11.019] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 11/21/2008] [Accepted: 11/24/2008] [Indexed: 12/24/2022]
Abstract
Membrane receptors are often modulated by steroids and it is necessary to distinguish the effects of steroids at these receptors from effects occurring at nuclear receptors. Additionally, it may also be mechanistically important to distinguish between direct effects caused by binding of steroids to membrane receptors and indirect effects on membrane receptor function caused by steroid perturbation of the membrane containing the receptor. In this regard, ent-steroids, the mirror images of naturally occurring steroids, are novel tools for distinguishing between these various actions of steroids. The review provides a background for understanding the different actions that can be expected of steroids and ent-steroids in biological systems, references for the preparation of ent-steroids, a short discussion about relevant forms of stereoisomerism and the requirements that need to be fulfilled for the interaction between two molecules to be enantioselective. The review then summarizes results of biophysical, biochemical and pharmacological studies published since 1992 in which ent-steroids have been used to investigate the actions of steroids in membranes and/or receptor-mediated signaling pathways.
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Affiliation(s)
- Douglas F Covey
- Department of Developmental Biology, Campus Box 8103, Washington Univ. in St. Louis, School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, United States.
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Joksovic PM, Covey DF, Todorovic SM. Inhibition of T-type calcium current in the reticular thalamic nucleus by a novel neuroactive steroid. Ann N Y Acad Sci 2008; 1122:83-94. [PMID: 18077566 DOI: 10.1196/annals.1403.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Neurons of the nucleus reticularis of the thalamus (nRT) serve as an important inhibitory gate that controls trafficking of thalamocortical sensory signals and states of sleep, arousal, and epilepsy. T-type calcium channels in nRT play a crucial role in the subthreshold excitability of these neurons, but their modulation by neuroactive steroids has not been previously studied. Here we explored the effect of (3beta,5beta,17beta)-3-hydroxyandrostane-17-carbonitrile (3beta-OH), a novel neuroactive steroid on T-type currents recorded from nRT neurons in intact brain slices of young rats. We found in voltage-clamp experiments that 3beta-OH potently and reversibly decreased T-type Ca(2+) current amplitude and stabilized inactive states of the channels. In current-clamp experiments, 3beta-OH significantly decreased the frequency of action potential firing from negative membrane potentials and minimally changed passive membrane properties. Our results indicate that 5beta-reduced neuroactive steroids, through the mechanisms of inhibition of T-type Ca(2+) currents and diminished spike firing in nRT neurons, may be important agents in control of sensory information processing in physiological conditions and possibly pathological brain states associated with increased cellular excitability such as epilepsy and/or tissue ischemia/hypoxia.
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Affiliation(s)
- Pavle M Joksovic
- Department of Anesthesiology, University of Virginia Health System, P.O. Box 800710, Charlottesville, VA 22908-0710, USA
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Abstract
Membrane-initiated cellular responses to steroids include modulation of ion channel activities via signal transduction pathways. However, the molecular mechanisms involved in nongenomic actions remain only partially understood. Our research has focused on the rapid effects of 1alpha,25(OH)(2) Vitamin D(3) [1,25D] on L-type Ca(2+) [L-Ca] and DIDS-sensitive Cl(-) channels in osteoblasts. Physiological nanomolar concentrations of hormonally active 1,25D promote rapid (1-5 min) potentiation of outward Cl(-) currents in osteosarcoma ROS 17/2.8 cells and mouse primary osteoblasts. In addition, 1,25D increases inward barium currents through L-Ca channels at low depolarizing potentials within seconds in a fashion similar to the 1,4-dihydropyridine [DHP] agonist Bay K8644. We found that second messenger cAMP is involved in 1,25D potentiation of Cl(-) and Ca(2+) channels. Nongenomic 1,25D effects on ion channel activities in osteoblasts appear to involve different mechanisms that include a possible direct interaction with the L-Ca channel molecule, on one hand, and signaling through the cAMP pathway, on the other. Rapid 1,25D actions on Cl(-) and Ca(2+) currents seem to couple to secretory activities in osteoblasts, thus contributing to bone mass formation.
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Affiliation(s)
- Laura P Zanello
- Department of Biochemistry, University of California, Riverside, 92521, USA.
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Pathirathna S, Todorovic SM, Covey DF, Jevtovic-Todorovic V. 5alpha-reduced neuroactive steroids alleviate thermal and mechanical hyperalgesia in rats with neuropathic pain. Pain 2006; 117:326-339. [PMID: 16150542 DOI: 10.1016/j.pain.2005.06.019] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Revised: 06/15/2005] [Accepted: 06/20/2005] [Indexed: 11/30/2022]
Abstract
5alpha-reduced neuroactive steroids with selective modulatory action in vitro on T or combined modulatory action on T and GABA(A) currents present in peripheral sensory neurons have been shown to induce potent peripheral analgesia in vivo in intact animals. Although the role of T and GABA(A) currents in pathophysiology of neuropathic pain (NPP) is not established, it appears that blockade of T currents and/or potentiation of GABA(A) currents could be beneficial in the management of NPP. To study the potential usefulness of 5alpha-reduced neuroactive steroids in alleviating NPP, we selected two newly synthesized steroids-ECN and CDNC24-with a selective blocking effect on T currents and a selective potentiating effect on GABA(A) currents, respectively, and commercial analogs-alphaxalone and 3alpha5alphaP-with the effects on both ion channels. We used a sciatic nerve ligation model to induce thermal and mechanical hyperalgesia in adult rats and tested peripheral thermal and mechanical nociception following local injection of neuroactive steroids into the peripheral receptive fields of a ligated hind paw. We found that 5alpha-reduced neuroactive steroids alleviate thermal and mechanical hyperalgesia in NPP rats. ECN and CDNC24 were more selective in alleviating thermal nociception in NPP than in sham animals when compared to 3alpha5alphaP and alphaxalone although the anti-nociceptive effect induced by 3alpha5alphaP and alphaxalone was more profound. CDNC24 was most selective since it had very minimal anti-nociceptive effect in sham animals but a very profound anti-nociceptive effect in NPP animals suggesting that, under pathological conditions, peripheral GABA(A) receptors might be an attractive therapeutic target.
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Affiliation(s)
- S Pathirathna
- Department of Anesthesiology, University of Virginia Health System, P.O. Box 800710, Charlottesville, VA 22908, USA Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Wen L, Yang S, Qiao H, Liu Z, Zhou W, Zhang Y, Huang P. SO-3, a new O-superfamily conopeptide derived from Conus striatus, selectively inhibits N-type calcium currents in cultured hippocampal neurons. Br J Pharmacol 2005; 145:728-39. [PMID: 15880145 PMCID: PMC1576188 DOI: 10.1038/sj.bjp.0706223] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Whole-cell currents in cultured hippocampal neurons were recorded to investigate the effects of SO-3, a new O-superfamily conopeptide derived from Conus striatus, on voltage-sensitive channels. SO-3 had no effect on voltage-sensitive sodium currents, delayed rectifier potassium currents, and transient outward potassium currents. Similar to the selective N-type calcium channel blocker omega-conotoxin MVIIA (MVIIA), SO-3 could concentration-dependently inhibit the high voltage-activated (HVA) calcium currents (I(Ca)). MVIIA(3 microM), 10 microM nimodipine, and 0.5 microM omega-agatoxin IVA (Aga) could selectively block the N-, L-, and P/Q-type I(Ca), which contributed approximately 32, approximately 38, and approximately 21% of the HVA currents in hippocampal neurons, respectively. About 31% of the total HVA currents were inhibited by 3 microM SO-3. SO-3 (3 microM) and 3 microM MVIIA inhibited the overlapping components of HVA currents, whereas no overlapping component was inhibited by 3 microM SO-3 and 10 microM nimodipine, or by 3 microM SO-3 and 0.5 microM Aga. Also, 3 microM SO-3 had no effect on R-type currents. SO-3 had less inhibitory effects on non-N-type HVA currents than MVIIA at higher concentrations (30 and 100 microM). The inhibitory effects of SO-3 and MVIIA on HVA currents were almost fully reversible. However, the recovery from block by MVIIA was more rapid than recovery from block by SO-3. It is concluded that SO-3 is a new omega-conotoxin selectively targeting N-type voltage-sensitive calcium channels. Considering the significance of N-type calcium channels for pain transduction, SO-3 may have therapeutic potential as a novel analgesic agent.
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Affiliation(s)
- Lei Wen
- Beijing Institute of Pharmacology and Toxicology, 27 Tai-Ping Road, Haidian District, Beijing 100850, China
| | - Sheng Yang
- Beijing Institute of Pharmacology and Toxicology, 27 Tai-Ping Road, Haidian District, Beijing 100850, China
| | - Haifa Qiao
- Beijing Institute of Pharmacology and Toxicology, 27 Tai-Ping Road, Haidian District, Beijing 100850, China
| | - Zhenwei Liu
- Beijing Institute of Pharmacology and Toxicology, 27 Tai-Ping Road, Haidian District, Beijing 100850, China
| | - Wenxia Zhou
- Beijing Institute of Pharmacology and Toxicology, 27 Tai-Ping Road, Haidian District, Beijing 100850, China
| | - Yongxiang Zhang
- Beijing Institute of Pharmacology and Toxicology, 27 Tai-Ping Road, Haidian District, Beijing 100850, China
- Author for correspondence:
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Pathirathna S, Brimelow BC, Jagodic MM, Krishnan K, Jiang X, Zorumski CF, Mennerick S, Covey DF, Todorovic SM, Jevtovic-Todorovic V. New evidence that both T-type calcium channels and GABAA channels are responsible for the potent peripheral analgesic effects of 5α-reduced neuroactive steroids. Pain 2005; 114:429-443. [PMID: 15777868 DOI: 10.1016/j.pain.2005.01.009] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Revised: 11/05/2004] [Accepted: 01/14/2005] [Indexed: 11/24/2022]
Abstract
Neurosteroids are potent blockers of neuronal low-voltage activated (T-type) Ca(2+) channels and potentiators of GABA(A) ligand-gated channels, but their effects in peripheral pain pathways have not been studied previously. To investigate potential analgesic effects and the ion channels involved, we tested the ability of locally injected 5alpha-reduced neurosteroids to modulate peripheral thermal nociception to radiant heat in adult rats in vivo and to modulate GABA(A) and T-type Ca(2+) channels in vitro. The steroid anesthetic alphaxalone (ALPX), the endogenous neurosteroid allopregnanolone (3alpha5alphaP), and a related compound ((3alpha,5alpha,17beta)-3-hydroxyandrostane-17-carbonitrile, (ACN)), induced potent, dose-dependent, enantioselective anti-nociception in vivo and modulation of both T-type Ca(2+) currents and GABA(A)-mediated currents in vitro. Analgesic effects of ALPX were incompletely antagonized by co-injections of the GABA(A) receptor antagonist bicuculline. The neurosteroid analogue ((3alpha,5alpha)-3-hydroxy-13,24-cyclo-18,21-dinorchol-22-en-24-ol (CDNC24), a compound with GABAergic but not T-type activity, was not analgesic. However, (3beta,5alpha,17beta)-17-hydroxyestrane-3-carbonitrile (ECN)), which has effects on T-type channels but not on GABA(A) receptors, also induced potent enantioselective peripheral anti-nociception. ECN increased pain thresholds less than ALPX, 3alpha5alphaP and ACN. However, when an ineffective dose of CDNC24 was combined with ECN, anti-nociceptive activity was greatly enhanced, and this effect was bicuculline-sensitive. These results strongly suggest that GABA(A) channels do not contribute to baseline pain transmission, but they can enhance anti-nociception mediated by blockade of T-type Ca(2+) channels. In conclusion, we demonstrate that potent peripheral analgesia induced by 5alpha-reduced neurosteroid is mediated in part by effects on T-type Ca(2+) channels. Our results also reveal a role of GABA-gated ion channels in peripheral nociceptive signaling.
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Affiliation(s)
- Sriyani Pathirathna
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA, USA Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St Louis, MO, USA Department of Psychiatry, Washington University School of Medicine, St Louis, MO, USA
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16
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Todorovic SM, Pathirathna S, Brimelow BC, Jagodic MM, Ko SH, Jiang X, Nilsson KR, Zorumski CF, Covey DF, Jevtovic-Todorovic V. 5beta-reduced neuroactive steroids are novel voltage-dependent blockers of T-type Ca2+ channels in rat sensory neurons in vitro and potent peripheral analgesics in vivo. Mol Pharmacol 2004; 66:1223-35. [PMID: 15280444 DOI: 10.1124/mol.104.002402] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
T-type Ca(2+) channels are believed to play an important role in pain perception, and anesthetic steroids such as alphaxalone and allopregnanolone, which have a 5alpha-configuration at the steroid A, B ring fusion, are known to inhibit T-type Ca(2+) channels and cause analgesia in a thermal nociceptive model (Soc Neurosci Abstr 29:657.9, 2003). To define further the structure-activity relationships for steroid analgesia, we synthesized and examined a series of 5beta-reduced steroids for their ability to induce thermal antinociception in rats when injected locally into the peripheral receptive fields of the nociceptors and studied their effects on T-type Ca(2+) channel function in vitro. We found that most of the steroids completely blocked T-type Ca(2+) currents in vitro with IC(50) values at a holding potential of -90 mV ranging from 2.8 to 40 microM. T current blockade exhibited mild voltage-dependence, suggesting that 5beta-reduced neuroactive steroids stabilize inactive states of the channel. For the most potent steroids, we found that other voltage-gated currents were not significantly affected at concentrations that produce nearly maximal blockade of T currents. All tested compounds induced dose-dependent analgesia in thermal nociceptive testing; the most potent effect (ED(50), 30 ng/100 microl) obtained with a compound [(3beta,5beta,17beta)-3-hydroxyandrostane-17-carbonitrile] that was also the most effective blocker of T currents. Compared with previously studied 5alpha-reduced steroids, these 5beta-reduced steroids are more efficacious blockers of neuronal T-type Ca(2+) channels and are potentially useful as new experimental reagents for understanding the role of neuronal T-type Ca(2+) channels in peripheral pain pathways.
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Affiliation(s)
- Slobodan M Todorovic
- Department of Anesthesiology, University of Virginia School of Medicine, Charlottesville, VA, USA
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17
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Affiliation(s)
- Jack D Schim
- North County Neurology Associates, Encinitas, California, USA.
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Takei T, Saegusa H, Zong S, Murakoshi T, Makita K, Tanabe T. Anesthetic sensitivities to propofol and halothane in mice lacking the R-type (Cav2.3) Ca2+ channel. Anesth Analg 2003; 97:96-103, table of contents. [PMID: 12818950 DOI: 10.1213/01.ane.0000065548.83253.5c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
UNLABELLED Because inhibition of voltage-dependent Ca(2+) channels can be a mechanism underlying general anesthesia, we examined sensitivities to propofol and halothane in mice lacking the R-type (Ca(v)2.3) channel widely expressed in neurons. Sleep time after propofol injection (26 mg/kg IV) and halothane MAC(RR) and MAC (50% effective concentrations for the loss of the righting reflex and for the tail pinch/withdrawal response, respectively) were determined. Significantly shorter propofol-induced sleep time (291.6 +/- 16.8 s versus 344.4 +/- 12.1 s) and larger halothane MAC(RR) (1.11% +/- 0.04% versus 0.98% +/- 0.03%) were observed in Ca(v)2.3 channel knockouts (Ca(v)2.3(-/-)) than in wild-type (Ca(v)2.3(+/+)) litter mates. To investigate the basis of the decreased anesthetic sensitivities in vivo, field excitatory postsynaptic potentials and population spikes (PSs) were recorded from Schaffer collateral CA1 synapses in hippocampal slices. Propofol (10-30 micro M) inhibited PSs by potentiating gamma-aminobutyric acid-ergic inhibition, and this potentiation was markedly smaller at 30 micro M in Ca(v)2.3(-/-) mice, possibly accounting for the decreased propofol sensitivity in vivo. Halothane (1.4%-2.2%) inhibited field excitatory postsynaptic potentials similarly in both genotypes, whereas 1%-2% halothane depressed PSs more in Ca(v)2.3(-/-) mice, suggesting the postsynaptic role of the R-type channel in the propagation of excitation and other mechanisms underlying the increased halothane MAC(RR) in Ca(v)2.3(-/-) mice. IMPLICATIONS Because inhibition of neuronal Ca(2+) currents can be a mechanism underlying general anesthesia, we examined anesthetic sensitivities in mice lacking the R-type (Ca(v)2.3) Ca(2+) channels both in vivo and in hippocampal slices. Decreased sensitivities in mutant mice imply a possibility that agents blocking this channel may increase the requirements of anesthetics/hypnotics.
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Affiliation(s)
- Tetsuhiro Takei
- Department of Anesthesiology, Graduate School of Medicine, Tokyo Medical and Dental University, Japan
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Moulder KL, Fu T, Melbostad H, Cormier RJ, Isenberg KE, Zorumski CF, Mennerick S. Ethanol-induced death of postnatal hippocampal neurons. Neurobiol Dis 2002; 10:396-409. [PMID: 12270700 DOI: 10.1006/nbdi.2002.0523] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Fetal alcohol exposure causes severe neuropsychiatric problems, but mechanisms of the ethanol-associated changes in central nervous system development are unclear. In vivo, ethanol's interaction with N-methyl-D-aspartate (NMDA) and gamma-aminobutyric acid type A (GABA(A)) receptors may cause increased apoptosis in the immature forebrain. We examined whether ethanol affects survival of neonatal hippocampal neurons in primary cultures. A 6-day ethanol exposure killed hippocampal neurons with an LD50 of approximately 25 mM. Elevated extracellular potassium or insulin-related growth factor 1 inhibited cell loss. Although potentiation of GABA(A) receptors or complete block of NMDA receptors also kills hippocampal neurons, pharmacological studies suggest that ethanol's interaction with GABA(A) and NMDA receptors is not sufficient to explain ethanol's effects on neuronal survival. Ca(2+) influx in response to depolarization was depressed >50% by chronic ethanol treatment. We suggest that chronic ethanol may promote neuronal loss through a mechanism affecting Ca(2+) influx in addition to effects on postsynaptic GABA and glutamate receptors.
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Affiliation(s)
- Krista L Moulder
- Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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20
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Heady TN, Gomora JC, Macdonald TL, Perez-Reyes E. Molecular pharmacology of T-type Ca2+ channels. JAPANESE JOURNAL OF PHARMACOLOGY 2001; 85:339-50. [PMID: 11388636 DOI: 10.1254/jjp.85.339] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Over the past few years increasing attention has been focused on T-type calcium channels and their possible physiological and pathophysiological roles. Efforts toward elucidating the exact role(s) of these calcium channels have been hampered by the lack of T-type specific antagonists, resulting in the subsequent use of less selective calcium channel antagonists. In addition, the activity of these blockers often varies with cell or tissue type, as well as recording conditions. This review summarizes a variety of compounds that exhibit varying degrees of blocking activity towards T-type Ca2+ channels. It is designed as an aid for researchers in need of antagonists to study the biophysical and pathological nature of T-type channels, as well as a starting point for those attempting to develop potent and selective antagonists of the channel.
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Affiliation(s)
- T N Heady
- Department of Chemistry, University of Virginia, Charlottesville 22904, USA
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21
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Nakashima YM, Pereverzev A, Schneider T, Covey DF, Lingle CJ. Blockade of Ba2+ current through human alpha1E channels by two steroid analogs, (+)-ACN and (+)-ECN. Neuropharmacology 1999; 38:843-55. [PMID: 10465688 DOI: 10.1016/s0028-3908(99)00013-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous work suggests that different neuroactive steroids may exhibit some selectivity in their blocking effects on different high-voltage activated (HVA) Ca2+ currents. At least some of these effects appear to involve direct blocking actions on Ca2+ channels. Thus, direct investigation of the effects of various steroids on cloned Ca2+ channel variants may lead to the development of potent and selective small-molecular weight Ca2+ channel blockers. Here we examine the effects of two steroids on a cloned human alpha1E Ca2+ channel both with and without a beta3 subunit, when expressed in HEK293 cells. One compound, (+)-ACN, has been previously shown to block N-, Q-, and R-subtypes of HVA current without affecting L- and P-type current. The second compound, (+)-ECN, weakly blocks total HVA current in hippocampal neurons. (+)-ECN differs from (+)-ACN in lacking effects on GABA receptors, but shares with (+)-ACN an ability to partially inhibit T current in DRG neurons (Todorovic, S.M., Prakriya, M., Nakashima, Y.M. et al., 1998. Enantioselective blockade of T-type Ca2+ current in adult rat sensory neurons by a steroid lacking GABA-mimetic activity. Mol. Pharmacol. 54, 918-927). (+)-ACN can block 100% of Ba2+ current in HEK cells arising either from the alpha1E subunit (IC50 approximate to 10 microM) or the alpha1Ebeta3 combination (IC50 approximate to 5 microM), while (+)-ECN maximally blocks only about 80% of the alpha1E (10 microM) or alpha1Ebeta3 (16 microM) current. Blockade by (+)-ACN exhibits several differences from blockade by (+)-ECN. (+)-ACN increases the apparent rate of onset of inactivation, particularly for the alpha1E variant, slows recovery from inactivation, and more profoundly shifts the voltage-dependence of current availability for both alpha1E and alpha1Ebeta3 variants than does (+)-ECN. Although the complexity of the normal inactivation kinetics of alpha1E variants makes interpretation of the (+)-ACN-induced kinetic alterations difficult, the results suggest that the two steroids are to some extent acting by distinct mechanisms, and perhaps at different sites.
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Affiliation(s)
- Y M Nakashima
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Norton RS, Pallaghy PK, Baell JB, Wright CE, Lew MJ, Angus JA. Polypeptide ?-conotoxin GVIA as a basis for new analgesic and neuroprotective agents. Drug Dev Res 1999. [DOI: 10.1002/(sici)1098-2299(199903/04)46:3/4<206::aid-ddr6>3.0.co;2-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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23
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Todorovic SM, Prakriya M, Nakashima YM, Nilsson KR, Han M, Zorumski CF, Covey DF, Lingle CJ. Enantioselective blockade of T-type Ca2+ current in adult rat sensory neurons by a steroid that lacks gamma-aminobutyric acid-modulatory activity. Mol Pharmacol 1998; 54:918-27. [PMID: 9804627 DOI: 10.1124/mol.54.5.918] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A number of steroids seem to have anesthetic effects resulting primarily from their ability to potentiate currents gated by gamma-aminobutyric acidA (GABAA) receptor activation. One such compound is (3alpha,5alpha, 17beta)-3-hydroxyandrostane-17-carbonitrile [(+)-ACN]. We were interested in whether carbonitrile substitution at other ring positions might result in other pharmacological consequences. Here we examine effects of (3beta,5alpha, 17beta)-17-hydroxyestrane-3-carbonitrile [(+)-ECN] on GABAA receptors and Ca2+ channels. In contrast to (+)-ACN, (+)-ECN does not potentiate GABAA-receptor activated currents, nor does it directly gate GABAA-receptor mediated currents. However, both steroids produce an enantioselective reduction of T-type current. (+)-ECN blocked T current with an IC50 value of 0.3 microM with a maximal block of 41%. (+)-ACN produced a partial block of T current (44% maximal block) with an IC50 value of 0.4 microM. Block of T current showed mild use- and voltage-dependence. The (-)-ECN enantiomer was about 33 times less potent than (+)-ECN, with an IC50 value of 10 microM and an amount of maximal block comparable to (+)-ECN. (+)-ECN was less effective at blocking high-voltage-activated Ca2+ current in DRG neurons (IC50 value of 9. 3 microM with maximal block of about 27%) and hippocampal neurons. (+)-ECN (10 microM) had minimal effects on voltage-gated sodium and potassium currents in rat chromaffin cells. The results identify a steroid with no effects on GABAA receptors that produces a partial inhibition of T-type Ca2+ current with reasonably high affinity and selectivity. Further study of steroid actions on T currents may lead to even more selective and potent agents.
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Affiliation(s)
- S M Todorovic
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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