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Abstract
The term neurosteroid refers to rapid membrane actions of steroid hormones and their derivatives that can modulate physiological functions and behavior via their interactions with ligand-gated ion channels. This chapter will highlight recent advances pertaining to the modulatory effects of a select group of neurosteroids that are primarily potent positive allosteric modulators of γ-aminobutyric acidA receptors (GABAARs). Nanomolar concentrations of neurosteroids, which occur in vivo, potentiate phasic and tonic forms of GABAAR-mediated inhibition, indicating that both synaptic and extrasynaptic GABAARs possess sensitivity to neurosteroids and contribute to the overall ability of neurosteroids to modulate central nervous system excitability. Common effects of alcohol and neurosteroids at GABAARs have stimulated research on the ability of neurosteroids to modulate alcohol's acute and chronic effects. Background on neurosteroid pharmacology and biosynthetic enzymes will be provided as it relates to experimental findings. Data will be summarized on alcohol and neurosteroid interactions across neuroanatomical regions and models of intoxication, consumption, dependence, and withdrawal. Evidence supports independent regulation of neurosteroid synthesis between periphery and brain as well as across brain regions following acute alcohol administration and during withdrawal. Local mechanisms for fine-tuning neuronal excitability via manipulation of neurosteroid synthesis exert predicted behavioral and electrophysiological responses on GABAAR-mediated inhibition. Collectively, targeting neurosteroidogenesis may be a beneficial treatment strategy for alcohol use disorders.
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Nipper MA, Jensen JP, Helms ML, Ford MM, Crabbe JC, Rossi DJ, Finn DA. Genotype Differences in Sensitivity to the Anticonvulsant Effect of the Synthetic Neurosteroid Ganaxolone during Chronic Ethanol Withdrawal. Neuroscience 2018; 397:127-137. [PMID: 30513375 DOI: 10.1016/j.neuroscience.2018.11.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 11/26/2018] [Accepted: 11/28/2018] [Indexed: 01/05/2023]
Abstract
Sensitivity to anticonvulsant effects of the γ-aminobutyric acidA receptor-active neurosteroid allopregnanolone (ALLO) during ethanol withdrawal varies across genotypes, with high sensitivity in genotypes with mild withdrawal and low sensitivity in genotypes with high withdrawal. The present studies determined whether the resistance to ALLO during withdrawal in mouse genotypes with high handling-induced convulsions (HICs) during withdrawal could be overcome with use of ganaxolone (GAN), the metabolically stable derivative of ALLO. In separate studies, male and female Withdrawal Seizure-Prone (WSP-1) and DBA/2J (D2) mice were exposed to air (controls) or 72-h ethanol vapor and then were scored for HICs during withdrawal (hourly for the first 12 h, then at hours 24 and 25). After the HIC scoring at hours 5 and 9, mice were injected with 10 mg/kg GAN or vehicle. Area under the HIC curve (AUC) for hours 5-12 was analyzed. In control WSP-1 mice, GAN significantly reduced AUC by 52% (males) and 63% (females), with effects that were absent or substantially reduced during withdrawal. In contrast, GAN significantly reduced AUC in both control and ethanol-withdrawing male and female D2 mice. AUC was decreased by 81% (males) and 70% (females) in controls and by 35% (males) and 21% (females) during withdrawal. The significant anticonvulsant effect of GAN during withdrawal in D2 but not WSP-1 mice suggests that different mechanisms may contribute to ALLO insensitivity during withdrawal in these two genotypes. Importantly, the results in D2 mice suggest that GAN may be a useful treatment for ethanol withdrawal-induced seizures.
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Affiliation(s)
- Michelle A Nipper
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States.
| | - Jeremiah P Jensen
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States
| | - Melinda L Helms
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States
| | - Matthew M Ford
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States; Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006, United States
| | - John C Crabbe
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States; Portland Alcohol Research Center, VA Portland Health Care System, Portland, OR 97239, United States
| | - David J Rossi
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States; Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, United States
| | - Deborah A Finn
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States; Portland Alcohol Research Center, VA Portland Health Care System, Portland, OR 97239, United States
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Effects of neonatal and adolescent neuroactive steroid manipulation on locomotor activity induced by ethanol in male wistar rats. Behav Brain Res 2017; 330:68-74. [DOI: 10.1016/j.bbr.2017.05.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 04/24/2017] [Accepted: 05/03/2017] [Indexed: 11/20/2022]
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Tanchuck-Nipper MA, Ford MM, Hertzberg A, Beadles-Bohling A, Cozzoli DK, Finn DA. Sex Differences in Ethanol's Anxiolytic Effect and Chronic Ethanol Withdrawal Severity in Mice with a Null Mutation of the 5α-Reductase Type 1 Gene. Behav Genet 2014; 45:354-67. [PMID: 25355320 DOI: 10.1007/s10519-014-9691-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 10/16/2014] [Indexed: 02/04/2023]
Abstract
Manipulation of endogenous levels of the GABAergic neurosteroid allopregnanolone alters sensitivity to some effects of ethanol. Chronic ethanol withdrawal decreases activity and expression of 5α-reductase-1, an important enzyme in allopregnanolone biosynthesis encoded by the 5α-reductase-1 gene (Srd5a1). The present studies examined the impact of Srd5a1 deletion in male and female mice on several acute effects of ethanol and on chronic ethanol withdrawal severity. Genotype and sex did not differentially alter ethanol-induced hypothermia, ataxia, hypnosis, or metabolism, but ethanol withdrawal was significantly lower in female versus male mice. On the elevated plus maze, deletion of the Srd5a1 gene significantly decreased ethanol's effect on total entries versus wildtype (WT) mice and significantly decreased ethanol's anxiolytic effect in female knockout (KO) versus WT mice. The limited sex differences in the ability of Srd5a1 genotype to modulate select ethanol effects may reflect an interaction between developmental compensations to deletion of the Srd5a1 gene with sex hormones and levels of endogenous neurosteroids.
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Affiliation(s)
- Michelle A Tanchuck-Nipper
- Department of Behavioral Neuroscience, VAMC Research (R&D-49), Oregon Health & Science University, 3710 SW, U.S. Veterans Hospital Road, Portland, OR, 97239, USA,
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Maldonado-Devincci AM, Cook JB, O'Buckley TK, Morrow DH, McKinley RE, Lopez MF, Becker HC, Morrow AL. Chronic intermittent ethanol exposure and withdrawal alters (3α,5α)-3-hydroxy-pregnan-20-one immunostaining in cortical and limbic brain regions of C57BL/6J mice. Alcohol Clin Exp Res 2014; 38:2561-71. [PMID: 25293837 DOI: 10.1111/acer.12530] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 07/15/2014] [Indexed: 02/03/2023]
Abstract
BACKGROUND The GABAergic neuroactive steroid (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP; allopregnanolone) has been studied during withdrawal from ethanol (EtOH) in humans, rats, and mice. Serum 3α,5α-THP levels decreased, and brain levels were not altered following acute EtOH administration (2 g/kg) in male C57BL/6J mice; however, the effects of chronic intermittent ethanol (CIE) exposure on 3α,5α-THP levels have not been examined. Given that CIE exposure changes subsequent voluntary EtOH drinking in a time-dependent fashion following repeated cycles of EtOH exposure, we conducted a time-course analysis of CIE effects on 3α,5α-THP levels in specific brain regions known to influence drinking behavior. METHODS Adult male C57BL/6J mice were exposed to 4 cycles of CIE to induce EtOH dependence. All mice were sacrificed and perfused at 1 of 2 time points, 8 or 72 hours following the final exposure cycle. Free-floating brain sections (40 μm; 3 to 5 sections/region/animal) were immunostained and analyzed to determine relative levels of cellular 3α,5α-THP. RESULTS Withdrawal from CIE exposure produced time-dependent and region-specific effects on immunohistochemical detection of 3α,5α-THP levels across cortical and limbic brain regions. A transient reduction in 3α,5α-THP immunoreactivity was observed in the central nucleus of the amygdala 8 hours after withdrawal from CIE (-31.4 ± 9.3%). Decreases in 3α,5α-THP immunoreactivity were observed 72 hours following withdrawal in the medial prefrontal cortex (-25.0 ± 9.3%), nucleus accumbens core (-29.9 ± 6.6%), and dorsolateral striatum (-18.5 ± 6.0%), while an increase was observed in the CA3 pyramidal cell layer of the hippocampus (+42.8 ± 19.5%). Sustained reductions in 3α,5α-THP immunoreactivity were observed at both time points in the lateral amygdala (8 hours -28.3 ± 12.8%; 72 hours -27.5 ± 12.4%) and in the ventral tegmental area (8 hours -26.5 ± 9.9%; 72 hours -31.6 ± 13.8%). CONCLUSIONS These data suggest that specific neuroadaptations in 3α,5α-THP levels may be present in regions of brain that mediate anxiety, stress, and reinforcement relevant to EtOH dependence. The changes that occur at different time points likely modulate neurocircuitry involved in EtOH withdrawal as well as the elevated drinking observed after CIE exposure.
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Affiliation(s)
- Antoniette M Maldonado-Devincci
- Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Snelling C, Tanchuck-Nipper MA, Ford MM, Jensen JP, Cozzoli DK, Ramaker MJ, Helms M, Crabbe JC, Rossi DJ, Finn DA. Quantification of ten neuroactive steroids in plasma in Withdrawal Seizure-Prone and -Resistant mice during chronic ethanol withdrawal. Psychopharmacology (Berl) 2014; 231:3401-14. [PMID: 24871700 PMCID: PMC4134998 DOI: 10.1007/s00213-014-3618-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2013] [Accepted: 05/08/2014] [Indexed: 12/22/2022]
Abstract
RATIONALE The rapid membrane actions of neuroactive steroids, particularly via an enhancement of γ-aminobutyric acidA receptors (GABAARs), participate in the regulation of central nervous system excitability. Prior evidence suggests an inverse relationship between endogenous GABAergic neuroactive steroid levels and behavioral changes in excitability during ethanol withdrawal. OBJECTIVES Previously, we found that ethanol withdrawal significantly decreased plasma allopregnanolone (ALLO) levels, a potent GABAergic neuroactive steroid, and decreased GABAAR sensitivity to ALLO in Withdrawal Seizure-Prone (WSP) but not in Withdrawal Seizure-Resistant (WSR) mice. However, the effect of ethanol withdrawal on levels of other endogenous GABAAR-active steroids is not known. METHODS After validation of a gas chromatography-mass spectrometry method for the simultaneous quantification of ten neuroactive steroids, we analyzed plasma from control male WSP-1 and WSR-1 mice and during ethanol withdrawal. RESULTS We quantified levels of nine neuroactive steroids in WSP-1 and WSR-1 plasma; levels of pregnanolone were not detectable. Basal levels of five neuroactive steroids were higher in WSR-1 versus WSP-1 mice. Ethanol withdrawal significantly suppressed five neuroactive steroids in WSP-1 and WSR-1 mice, including ALLO. CONCLUSIONS Due to lower basal levels of some GABAAR-active steroids in WSP-1 mice, a withdrawal-induced decrease in WSP-1 mice may have a greater physiological consequence than a similar decrease in WSR-1 mice. Because WSP-1 mice also exhibit a reduction in GABAAR sensitivity to neuroactive steroids during withdrawal, it is possible that the combined decrease in neuroactive steroids and GABAAR sensitivity during ethanol withdrawal in WSP-1 mice represents a neurochemical substrate for severe ethanol withdrawal.
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Affiliation(s)
- Christopher Snelling
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
| | | | - Matthew M. Ford
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR
| | - Jeremiah P. Jensen
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
| | - Debra K. Cozzoli
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
| | - Marcia J. Ramaker
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
| | - Melinda Helms
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
| | - John C. Crabbe
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
- Portland Alcohol Research Center, Department of Veterans Affairs Medical Center, Portland OR
| | - David J. Rossi
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
| | - Deborah A. Finn
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR
- Portland Alcohol Research Center, Department of Veterans Affairs Medical Center, Portland OR
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Doyon WM, Thomas AM, Ostroumov A, Dong Y, Dani JA. Potential substrates for nicotine and alcohol interactions: a focus on the mesocorticolimbic dopamine system. Biochem Pharmacol 2013; 86:1181-93. [PMID: 23876345 DOI: 10.1016/j.bcp.2013.07.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Revised: 07/11/2013] [Accepted: 07/12/2013] [Indexed: 01/13/2023]
Abstract
Epidemiological studies consistently find correlations between nicotine and alcohol use, yet the neural mechanisms underlying their interaction remain largely unknown. Nicotine and alcohol (i.e., ethanol) share many common molecular and cellular targets that provide potential substrates for nicotine-alcohol interactions. These targets for interaction often converge upon the mesocorticolimbic dopamine system, where the link to drug self-administration and reinforcement is well documented. Both nicotine and alcohol activate the mesocorticolimbic dopamine system, producing downstream dopamine signals that promote the drug reinforcement process. While nicotine primarily acts via nicotinic acetylcholine receptors, alcohol acts upon a wider range of receptors and molecular substrates. The complex pharmacological profile of these two drugs generates overlapping responses that ultimately intersect within the mesocorticolimbic dopamine system to promote drug use. Here we will examine overlapping targets between nicotine and alcohol and provide evidence for their interaction. Based on the existing literature, we will also propose some potential targets that have yet to be directly tested. Mechanistic studies that examine nicotine-alcohol interactions would ultimately improve our understanding of the factors that contribute to the associations between nicotine and alcohol use.
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Affiliation(s)
- William M Doyon
- Center on Addiction, Learning, Memory, Baylor College of Medicine, Houston, TX 77030, USA
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