151
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Structural basis for alcohol modulation of a pentameric ligand-gated ion channel. Proc Natl Acad Sci U S A 2011; 108:12149-54. [PMID: 21730162 DOI: 10.1073/pnas.1104480108] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Despite its long history of use and abuse in human culture, the molecular basis for alcohol action in the brain is poorly understood. The recent determination of the atomic-scale structure of GLIC, a prokaryotic member of the pentameric ligand-gated ion channel (pLGIC) family, provides a unique opportunity to characterize the structural basis for modulation of these channels, many of which are alcohol targets in brain. We observed that GLIC recapitulates bimodal modulation by n-alcohols, similar to some eukaryotic pLGICs: methanol and ethanol weakly potentiated proton-activated currents in GLIC, whereas n-alcohols larger than ethanol inhibited them. Mapping of residues important to alcohol modulation of ionotropic receptors for glycine, γ-aminobutyric acid, and acetylcholine onto GLIC revealed their proximity to transmembrane cavities that may accommodate one or more alcohol molecules. Site-directed mutations in the pore-lining M2 helix allowed the identification of four residues that influence alcohol potentiation, with the direction of their effects reflecting α-helical structure. At one of the potentiation-enhancing residues, decreased side chain volume converted GLIC into a highly ethanol-sensitive channel, comparable to its eukaryotic relatives. Covalent labeling of M2 positions with an alcohol analog, a methanethiosulfonate reagent, further implicated residues at the extracellular end of the helix in alcohol binding. Molecular dynamics simulations elucidated the structural consequences of a potentiation-enhancing mutation and suggested a structural mechanism for alcohol potentiation via interaction with a transmembrane cavity previously termed the "linking tunnel." These results provide a unique structural model for independent potentiating and inhibitory interactions of n-alcohols with a pLGIC family member.
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152
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Rico EP, Rosemberg DB, Langoni ADS, Souto AA, Dias RD, Bogo MR, Bonan CD, Souza DO. Chronic ethanol treatment alters purine nucleotide hydrolysis and nucleotidase gene expression pattern in zebrafish brain. Neurotoxicology 2011; 32:871-8. [PMID: 21704070 DOI: 10.1016/j.neuro.2011.05.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 04/12/2011] [Accepted: 05/23/2011] [Indexed: 12/20/2022]
Abstract
Ethanol is a widely consumed drug that acts on the central nervous system (CNS), modifying several signal transduction pathways activated by hormones and neurotransmitters. The zebrafish is an experimental model for the study of human diseases and the use of this species in biochemical and behavioral studies on alcoholism and alcohol-dependence has increased recently. However, there are no data concerning the effects of chronic ethanol exposure on the purinergic system, where extracellular nucleotides act as signaling molecules. Purinergic signaling is controlled by a group of enzymes named ectonucleotidases, which include NTPDases and ecto-5'-nucleotidase already characterized in zebrafish brain. The aim of this study was to evaluate nucleotide hydrolysis by NTPDases and ecto-5'-nucleotidase after long-term ethanol exposure. Additionally, the gene expression patterns of NTPDases1-3 and 5'-nucleotidase were determined. Animals were exposed to 0.5% ethanol for 7, 14, and 28 days. There were no significant changes in ATP and GTP hydrolysis after all treatments. However, a decrease in ADP (46% and 34%) and GDP (48% and 36%) hydrolysis was verified after 7 and 14 days, respectively. After 7 and 14 days of ethanol exposure, a significant decrease in AMP hydrolysis (48% and 36%) was also observed, whereas GMP hydrolysis was inhibited only after 7 days (46%). NTPDase2_mv and NTPDase3 mRNA transcript levels decreased after 7 and 14 days, respectively. In contrast, ethanol increased NTPDase1, NTPDase2_mq, and NTPDase3 transcript levels after 28 days of exposure. NTPDase2_mg and 5'-nucleotidase gene expression was not altered. Therefore, the ectonucleotidase pathway may be a target of chronic ethanol toxicity and the regulation of purinergic system could play a key role in the neurochemical mechanisms underlying the effects of ethanol on the CNS.
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Affiliation(s)
- Eduardo Pacheco Rico
- Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul. Rua Ramiro Barcelos 2600-Anexo, 90035-003 Porto Alegre, RS, Brazil.
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153
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Howard RJ, Slesinger PA, Davies DL, Das J, Trudell JR, Harris RA. Alcohol-binding sites in distinct brain proteins: the quest for atomic level resolution. Alcohol Clin Exp Res 2011; 35:1561-73. [PMID: 21676006 DOI: 10.1111/j.1530-0277.2011.01502.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Defining the sites of action of ethanol on brain proteins is a major prerequisite to understanding the molecular pharmacology of this drug. The main barrier to reaching an atomic-level understanding of alcohol action is the low potency of alcohols, ethanol in particular, which is a reflection of transient, low-affinity interactions with their targets. These mechanisms are difficult or impossible to study with traditional techniques such as radioligand binding or spectroscopy. However, there has been considerable recent progress in combining X-ray crystallography, structural modeling, and site-directed mutagenesis to define the sites and mechanisms of action of ethanol and related alcohols on key brain proteins. We review such insights for several diverse classes of proteins including inwardly rectifying potassium, transient receptor potential, and neurotransmitter-gated ion channels, as well as protein kinase C epsilon. Some common themes are beginning to emerge from these proteins, including hydrogen bonding of the hydroxyl group and van der Waals interactions of the methylene groups of ethanol with specific amino acid residues. The resulting binding energy is proposed to facilitate or stabilize low-energy state transitions in the bound proteins, allowing ethanol to act as a "molecular lubricant" for protein function. We discuss evidence for characteristic, discrete alcohol-binding sites on protein targets, as well as evidence that binding to some proteins is better characterized by an interaction region that can accommodate multiple molecules of ethanol.
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Affiliation(s)
- Rebecca J Howard
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Texas 77812, USA.
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154
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Cannabinoid potentiation of glycine receptors contributes to cannabis-induced analgesia. Nat Chem Biol 2011; 7:296-303. [PMID: 21460829 DOI: 10.1038/nchembio.552] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 02/16/2011] [Indexed: 02/07/2023]
Abstract
Cannabinoids enhance the function of glycine receptors (GlyRs). However, little is known about the mechanisms and behavioral implication of cannabinoid-GlyR interaction. Using mutagenesis and NMR analysis, we have identified a serine at 296 in the GlyR protein critical for the potentiation of I(Gly) by Δ(9)-tetrahydrocannabinol (THC), a major psychoactive component of marijuana. The polarity of the amino acid residue at 296 and the hydroxyl groups of THC are critical for THC potentiation. Removal of the hydroxyl groups of THC results in a compound that does not affect I(Gly) when applied alone but selectively antagonizes cannabinoid-induced potentiating effect on I(Gly) and analgesic effect in a tail-flick test in mice. The cannabinoid-induced analgesia is absent in mice lacking α3GlyRs but not in those lacking CB1 and CB2 receptors. These findings reveal a new mechanism underlying cannabinoid potentiation of GlyRs, which could contribute to some of the cannabis-induced analgesic and therapeutic effects.
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155
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Treutlein J, Rietschel M. Genome-wide association studies of alcohol dependence and substance use disorders. Curr Psychiatry Rep 2011; 13:147-55. [PMID: 21253885 DOI: 10.1007/s11920-011-0176-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Genome-wide association studies (GWAS) currently represent the most systematic approach to genetic research into complex disorders. They can detect associations of common variants in genomic regions in the absence of an a priori assumption. Most of the GWAS of addiction performed to date have focused on alcohol dependence or smoking behavior. Four GWAS of alcohol dependence have been published thus far, and only two single nucleotide polymorphisms have received modest support of replication in a subsequent study. Many more GWAS have been conducted for smoking behavior. One large, single GWAS and meta-analyses of the phenotype "smoking quantity" have generated convincing evidence for the contribution of variants in genes for cholinergic nicotinic receptor subunits. This article focuses on GWAS of alcohol addiction and provides an overview of GWAS of other substance abuse disorders.
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Affiliation(s)
- Jens Treutlein
- Department of Genetic Epidemiology in Psychiatry, Central Institute of Mental Health Mannheim (CIMH), University of Heidelberg, J5, 68159 Mannheim, Germany.
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156
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Ethanol affects striatal interneurons directly and projection neurons through a reduction in cholinergic tone. Neuropsychopharmacology 2011; 36:1033-46. [PMID: 21289603 PMCID: PMC3077272 DOI: 10.1038/npp.2010.241] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The acute effects of ethanol on the neurons of the striatum, a basal ganglia nucleus crucially involved in motor control and action selection, were investigated using whole-cell recordings. An intoxicating concentration of ethanol (50 mM) produced inhibitory effects on striatal large aspiny cholinergic interneurons (LAIs) and low-threshold spike interneurons (LTSIs). These effects persisted in the presence of tetrodotoxin and were because of an increase in potassium currents, including those responsible for medium and slow afterhyperpolarizations. In contrast, fast-spiking interneurons (FSIs) were directly excited by ethanol, which depolarized these neurons through the suppression of potassium currents. Medium spiny neurons (MSNs) became hyperpolarized in the presence of ethanol, but this effect did not persist in the presence of tetrodotoxin and was mimicked and occluded by application of the M1 muscarinic receptor antagonist telenzepine. Ethanol effects on MSNs were also abolished by 100 μM barium. This showed that the hyperpolarizations observed in MSNs were because of decreased tonic activation of M1 muscarinic receptors, resulting in an increase in Kir2 conductances. Evoked GABAergic responses of MSNs were reversibly decreased by ethanol with no change in paired-pulse ratio. Furthermore, ethanol impaired the ability of thalamostriatal inputs to inhibit a subsequent corticostriatal glutamatergic response in MSNs. These results offer the first comprehensive description of the highly cell type-specific effects of ethanol on striatal neurons and provide a cellular basis for the interpretation of ethanol influence on a brain area crucially involved in the motor and decisional impairment caused by this drug.
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157
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Dou X, Menkari CE, Shanmugasundararaj S, Miller KW, Charness ME. Two alcohol binding residues interact across a domain interface of the L1 neural cell adhesion molecule and regulate cell adhesion. J Biol Chem 2011; 286:16131-9. [PMID: 21367865 DOI: 10.1074/jbc.m110.209254] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ethanol may cause fetal alcohol spectrum disorders (FASD) in part by inhibiting cell adhesion mediated by the L1 neural cell adhesion molecule. Azialcohols photolabel Glu-33 and Tyr-418, two residues that are predicted by homology modeling to lie within 2.8 Å of each other at the interface between the Ig1 and Ig4 domains of L1 (Arevalo, E., Shanmugasundararaj, S., Wilkemeyer, M. F., Dou, X., Chen, S., Charness, M. E., and Miller, K. W. (2008) Proc. Natl. Acad. Sci. U.S.A. 105, 371-375). Using transient transfection of NIH/3T3 cells with wild type (WT-L1) and mutated L1, we found that cysteine substitution of both residues (E33C/Y418C-L1) significantly increased L1 adhesion above levels observed for WT-L1 or the single cysteine substitutions E33C-L1 or Y418C-L1. The reducing agent β-mercaptoethanol (βME) reversibly decreased the adhesion of E33C/Y418C-L1, but had no effect on WT-L1, E33C-L1, or Y418C-L1. Thus, disulfide bond formation occurs between Cys-33 and Cys-418, confirming both the close proximity of these residues and the importance of Ig1-Ig4 interactions in L1 adhesion. Maximal ethanol inhibition of cell adhesion was significantly lower in cells expressing E33C/Y418C-L1 than in those expressing WT-L1, E33C-L1, or Y418C-L1. Moreover, the effects of βME and ethanol on E33C/Y418C-L1 adhesion were non-additive. The cutoff for alcohol inhibition of WT-L1 adhesion was between 1-butanol and 1-pentanol. Increasing the size of the alcohol binding pocket by mutating Glu-33 to Ala-33, increased the alcohol cutoff from 1-butanol to 1-decanol. These findings support the hypothesis that alcohol binding within a pocket bordered by Glu-33 and Tyr-418 inhibits L1 adhesion by disrupting the Ig1-Ig4 interaction.
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Affiliation(s)
- Xiaowei Dou
- Veterans Affairs Boston Healthcare System, Department of Neurology, Harvard Medical School, West Roxbury, Massachusetts 02132, USA
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158
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Steiner MA, Lecourt H, Strasser DS, Brisbare-Roch C, Jenck F. Differential effects of the dual orexin receptor antagonist almorexant and the GABA(A)-α1 receptor modulator zolpidem, alone or combined with ethanol, on motor performance in the rat. Neuropsychopharmacology 2011; 36:848-56. [PMID: 21150905 PMCID: PMC3055732 DOI: 10.1038/npp.2010.224] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Current insomnia treatments such as γ-aminobutyric acid (GABA) receptor modulators are associated with sedative and muscle-relaxant effects, which increase when drug intake is combined with alcohol. This study compared the novel sleep-enabling compound almorexant (ACT-078573-hydrochloride), a dual orexin receptor antagonist, with the positive GABA(A)-α1 receptor modulator zolpidem. Both compounds were administered alone or in combination with ethanol, and their effects on forced motor performance were determined in Wistar rats upon waking after treatment. To detect substance-induced sedation and myorelaxation, time spent on an accelerating rotating rod (rotarod) and forepaw grip strength were measured. Zolpidem (10, 30, and 100 mg/kg, p.o.) and ethanol (0.32, 1, and 1.5 g/kg, i.p.) dose-dependently decreased rotarod performance and grip strength, whereas almorexant (30, 100, and 300 mg/kg, p.o.) did not. Doses of ethanol (0.32 and 1 g/kg), which were ineffective when administered alone, showed interactions with zolpidem (10 and 30 mg/kg) leading to reduced rotarod performance and grip strength; in contrast, combination of ethanol (0.32 and 1 g/kg) with almorexant (100 and 300 mg/kg) did not reduce performance or grip strength below ethanol alone. We conclude that unlike zolpidem, almorexant does not interfere with forced motor performance or grip strength in the rat, nor does it further increase the sedative effects of ethanol. Our results suggest that the effect of almorexant can be immediately reversed to full alertness like under physiological sleep, and that almorexant is less likely to show strong sedation, excessive myorelaxation, or interaction with alcohol than commonly prescribed hypnotics such as zolpidem.
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Affiliation(s)
- Michel A Steiner
- CNS-Pharmacology, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland.
| | - Hugues Lecourt
- CNS-Pharmacology, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Daniel S Strasser
- CNS-Pharmacology, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
| | | | - François Jenck
- CNS-Pharmacology, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
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159
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Binge alcohol drinking is associated with GABAA alpha2-regulated Toll-like receptor 4 (TLR4) expression in the central amygdala. Proc Natl Acad Sci U S A 2011; 108:4465-70. [PMID: 21368176 DOI: 10.1073/pnas.1019020108] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Binge drinking (blood-alcohol levels ≥ 0.08 g% in a 2-h period), is a significant public health burden in need of improved treatment. Gene therapy may offer beneficial alternatives to current psychosocial and pharmacotherapeutic interventions, but identification of the target genes is a clinical challenge. We report that a GABA(A) α2 siRNA vector (pHSVsiLA2) infused into the central nucleus of the amygdala (CeA) of alcohol-preferring (P) rats caused profound and selective reduction of binge drinking associated with inhibition of α2 expression, decreased GABA(A) receptor density, and inhibition of Toll-like receptor 4 (TLR4). CeA infusion of a TLR4 siRNA vector (pHSVsiLTLR4a) also inhibited binge drinking, but neither vector functioned when infused into the ventral pallidum. Binge drinking was inhibited by a GABA(A) α1 siRNA vector (pHSVsiLA1) infused into the ventral pallidum, unrelated to TLR4. The vectors did not alter sucrose intake and a scrambled siRNA vector was negative. The data indicate that GABA(A) α2-regulated TLR4 expression in the CeA contributes to binge drinking and may be a key early neuroadaptation in excessive drinking.
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160
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Extrasynaptic delta-containing GABAA receptors in the nucleus accumbens dorsomedial shell contribute to alcohol intake. Proc Natl Acad Sci U S A 2011; 108:4459-64. [PMID: 21368141 DOI: 10.1073/pnas.1016156108] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent findings suggest that extrasynaptic δ-subunit-containing GABA(A) receptors are sensitive to low-to-moderate concentrations of alcohol, raising the possibility that these receptors mediate the reinforcing effects of alcohol after consumption of one or a few drinks. We used the technique of viral-mediated RNAi to reduce expression of the GABA(A) receptor δ-subunit in adult rats in localized regions of the nucleus accumbens (NAc) to test the hypothesis that δ-subunit-containing GABA(A) receptors in the NAc are necessary for oral alcohol consumption. We found that knockdown of the δ-subunit in the medial shell region of the NAc, but not in the ventral or lateral shell or in the core, reduced alcohol intake. In contrast, δ-subunit knockdown in the medial shell did not affect intake of a 2% sucrose solution, suggesting that the effects of GABA(A) receptor δ-subunit reduction are specific to alcohol. These results provide strong evidence that extrasynaptic δ-subunit-containing GABA(A) receptors in the medial shell of the NAc are critical for the reinforcing effects of oral ethanol.
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161
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Earl DE, Tietz EI. Inhibition of recombinant L-type voltage-gated calcium channels by positive allosteric modulators of GABAA receptors. J Pharmacol Exp Ther 2011; 337:301-11. [PMID: 21262851 DOI: 10.1124/jpet.110.178244] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Benzodiazepines (BDZs) depress neuronal excitability via positive allosteric modulation of inhibitory GABA(A) receptors (GABA(A)R). BDZs and other positive GABA(A)R modulators, including barbiturates, ethanol, and neurosteroids, can also inhibit L-type voltage-gated calcium channels (L-VGCCs), which could contribute to reduced neuronal excitability. Because neuronal L-VGCC function is up-regulated after long-term GABA(A)R modulator exposure, an interaction with L-VGCCs may also play a role in physical dependence. The current studies assessed the effects of BDZs (diazepam, flurazepam, and desalkylflurazepam), allopregnanolone, pentobarbital, and ethanol on whole-cell Ba(2+) currents through recombinant neuronal Ca(v)1.2 and Ca(v)1.3 L-VGCCs expressed with β(3) and α(2)δ-1 in HEK293T cells. Allopregnanolone was the most potent inhibitor (IC(50), ∼10 μM), followed by BDZs (IC(50), ∼50 μM), pentobarbital (IC(50), 0.3-1 mM), and ethanol (IC(50), ∼300 mM). Ca(v)1.3 channels were less sensitive to pentobarbital inhibition than Ca(v)1.2 channels, similar to dihydropyridine (DHP) L-VGCC antagonists. All GABA(A)R modulators induced a negative shift in the steady-state inactivation curve of Ca(v)1.3 channels, but only BDZs and pentobarbital induced a negative shift in Ca(v)1.2 channel inactivation. Mutation of the high-affinity DHP binding site (T1039Y and Q1043M) in Ca(v)1.2 channels reduced pentobarbital potency. Despite the structural similarity between benzothiazepines and BDZs, mutation of an amino acid important for diltiazem potency (I1150A) did not affect diazepam potency. Although L-VGCC inhibition by BDZs occurred at concentrations that are possibly too high to be clinically relevant and is not likely to play a role in the up-regulation of L-VGCCs during long-term treatment, pentobarbital and ethanol inhibited L-VGCCs at clinically relevant concentrations.
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Affiliation(s)
- Damien E Earl
- Department of Physiology and Pharmacology, University of Toledo College of Medicine, Health Science Campus, Toledo, OH 43614, USA
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162
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Bébarová M, Matejovič P, Pásek M, Ohlídalová D, Jansová D, Simurdová M, Simurda J. Effect of ethanol on action potential and ionic membrane currents in rat ventricular myocytes. Acta Physiol (Oxf) 2010; 200:301-14. [PMID: 20618172 DOI: 10.1111/j.1748-1716.2010.02162.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM Even though alcohol intoxication is often linked to arrhythmias, data describing ethanol effect on cardiac ionic channels are rare. In addition, ethanol is used as a solvent of hydrophobic compounds in experimental studies. We investigated changes of the action potential (AP) configuration and main ionic membrane currents in rat cardiomyocytes under 20-1500 m(M) ethanol. METHODS Experiments were performed on enzymatically isolated rat right ventricular myocytes using the whole cell patch-clamp technique at room temperature. RESULTS Ethanol reversibly decelerated the upstroke velocity and decreased AP amplitude and duration at 0.2 and 3 Hz. The fast sodium current I(Na) , l-type calcium current I(Ca) and transient outward potassium current I(to) were reversibly inhibited in a concentration-dependent manner (50% inhibition at 446 ± 12, 553 ± 49 and 1954 ± 234 m(M), respectively, with corresponding Hill coefficients 3.1 ± 0.3, 1.1 ± 0.2 and 0.9 ± 0.1). Suppression of I(Na) and I(Ca) magnitude was slightly voltage dependent. The effect on I(Ca) and I(to) was manifested mainly as an acceleration of their apparent inactivations with a decreased slow and fast time constant respectively. As a consequence of marked differences in n(H) , sensitivity of the currents to ethanol at 10% inhibition decreases in the following order: I(Ca) (75 mm, 3.5‰), I(to) (170 m(M), 7.8‰) and I(Na) (220 m(M), 10.1‰). CONCLUSION Our results suggest a slight inhibition of all the currents at ethanol concentrations relevant to deep alcohol intoxication. The concentration dependence measured over a wide range may serve as a guideline when using ethanol as a solvent.
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Affiliation(s)
- M Bébarová
- Department of Physiology, Masaryk University, Brno - Bohunice, Czech Republic.
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163
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Harris RA, Osterndorff-Kahanek E, Ponomarev I, Homanics GE, Blednov YA. Testing the silence of mutations: Transcriptomic and behavioral studies of GABA(A) receptor α1 and α2 subunit knock-in mice. Neurosci Lett 2010; 488:31-5. [PMID: 21056629 DOI: 10.1016/j.neulet.2010.10.075] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 10/28/2010] [Accepted: 10/29/2010] [Indexed: 12/13/2022]
Abstract
Knock-in mice were constructed with mutations in the α1 (H(270), A(277)) and α2 (H(270), A(277)) subunits of the GABAA receptor, which resulted in receptors that lacked modulation by ethanol but retained normal responses to GABA in vitro. A key question is whether these mutant receptors also function normally in vivo. Perturbation of brain function was evaluated by gene expression profiling in the cerebral cortex and by behavioral pharmacology experiments with GABAergic drugs. Analysis of individual transcripts found only six transcripts that were changed in α1 knock-in mice and three in the α2 mutants (p<0.05, corrected for multiple comparisons). Two transcripts that are sensitive to neuronal activity, Arc and Fos, increased about 250% in the α2 mutants, and about 50% in the α1 mutants. Behavioral effects (loss of righting reflex, rotarod) of flurazepam and pentobarbital were not different between α2 mutants and wild-type, but they were enhanced for α1 knock-in mice. These results indicate that introduction of these mutations in the α2 subunit of the GABAA receptor does not produce marked perturbation of brain function, as measured by gene expression and GABAergic behavioral responses, but the same mutations in the α1 subunit produce more pronounced changes, especially in GABAergic function.
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Affiliation(s)
- R A Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, 1 University Station, A4800, Austin, TX 78712, United States
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164
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Blednov YA, Borghese CM, McCracken ML, Benavidez JM, Geil CR, Osterndorff-Kahanek E, Werner DF, Iyer S, Swihart A, Harrison NL, Homanics GE, Harris RA. Loss of ethanol conditioned taste aversion and motor stimulation in knockin mice with ethanol-insensitive α2-containing GABA(A) receptors. J Pharmacol Exp Ther 2010; 336:145-54. [PMID: 20876231 DOI: 10.1124/jpet.110.171645] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
GABA type A receptors (GABA(A)-Rs) are potential targets of ethanol. However, there are multiple subtypes of this receptor, and, thus far, individual subunits have not been definitively linked with specific ethanol behavioral actions. Interestingly, though, a chromosomal cluster of four GABA(A)-R subunit genes, including α2 (Gabra2), was associated with human alcoholism (Am J Hum Genet 74:705-714, 2004; Pharmacol Biochem Behav 90:95-104, 2008; J Psychiatr Res 42:184-191, 2008). The goal of our study was to determine the role of receptors containing this subunit in alcohol action. We designed an α2 subunit with serine 270 to histidine and leucine 277 to alanine mutations that was insensitive to potentiation by ethanol yet retained normal GABA sensitivity in a recombinant expression system. Knockin mice containing this mutant subunit were tested in a range of ethanol behavioral tests. These mutant mice did not develop the typical conditioned taste aversion in response to ethanol and showed complete loss of the motor stimulant effects of ethanol. Conversely, they also demonstrated changes in ethanol intake and preference in multiple tests. The knockin mice showed increased ethanol-induced hypnosis but no difference in anxiolytic effects or recovery from acute ethanol-induced motor incoordination. Overall, these studies demonstrate that the effects of ethanol at GABAergic synapses containing the α2 subunit are important for specific behavioral effects of ethanol that may be relevant to the genetic linkage of this subunit with human alcoholism.
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Affiliation(s)
- Y A Blednov
- Waggoner Center for Alcohol and Addiction Research, University of Texas, 1 University Station, Austin, TX 78712, USA.
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165
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Abstract
Highly sensitive, label-free biodetection methods have applications in both the fundamental research and healthcare diagnostics arenas. Therefore, the development of new transduction methods and the improvement of the existing methods will significantly impact these areas. A brief overview of the different types of biosensors and the critical parameters governing their performance will be given. Additionally, a more in-depth discussion of optical devices, surface functionalization methods to increase device specificity, and fluidic techniques to improve sample delivery will be reviewed.
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Affiliation(s)
- Heather K Hunt
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, USA.
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166
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Ader L, Jones DNM, Lin H. Alcohol binding to the odorant binding protein LUSH: multiple factors affecting binding affinities. Biochemistry 2010; 49:6136-42. [PMID: 20550105 DOI: 10.1021/bi100540k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Density function theory (DFT) calculations have been carried out to investigate the binding of alcohols to the odorant binding protein LUSH from Drosophila melanogaster. LUSH is one of the few proteins known to bind to ethanol at physiologically relevant concentrations and where high-resolution structural information is available for the protein bound to alcohol at these concentrations. The structures of the LUSH-alcohol complexes identify a set of specific hydrogen-bonding interactions as critical for optimal binding of ethanol. A set of truncated models based on the structure of the LUSH-butanol complex were constructed for the wild-type and mutant (T57S, S52A, and T57A) proteins in complexes with a series of n-alcohols and for the apoprotein bound to water and for the ligand-free protein. Using both gas-phase calculations and continuum solvation model calculations, we found that the widely used DFT model, B3LYP, failed to reproduce the experimentally observed trend of increasing binding affinity with the increasing length of the alkyl chain in the alcohol. In contrast, the recently developed M05-2X DFT model successfully reproduced this subtle trend. Analysis of the results indicated that multiple factors contribute to the differences in alcohol binding affinity: the H-bonding with Thr57 and Ser52 (4-5 kcal/mol per H-bond), the desolvation contribution (4-6 kcal/mol for alcohols and 8-10 kcal/mol for water), and the other noncovalent interaction (1.2 kcal/mol per CH(2) group of the alcohol alkyl chain). These results reveal the outstanding potential for using the M05-2X model in calculations of protein-substrate complexes where noncovalent interactions are important.
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Affiliation(s)
- Lauren Ader
- Chemistry Department, University of Colorado Denver, Denver, Colorado 80217, USA
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167
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Mostile G, Jankovic J. Alcohol in essential tremor and other movement disorders. Mov Disord 2010; 25:2274-84. [DOI: 10.1002/mds.23240] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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168
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Gowin JL, Swann AC, Moeller FG, Lane SD. Zolmitriptan and human aggression: interaction with alcohol. Psychopharmacology (Berl) 2010; 210:521-31. [PMID: 20407761 PMCID: PMC9150756 DOI: 10.1007/s00213-010-1851-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 03/25/2010] [Indexed: 11/29/2022]
Abstract
RATIONALE The serotonin 1(B/D) (5-HT1(B/D)) receptor has shown potential as a target for decreasing aggression. The 5-HT1(B/D) agonist zolmitriptan's ability to reduce aggressive behavior in humans and its interaction with the well-known aggression-enhancing drug alcohol were examined. OBJECTIVES Our objective was to investigate zolmitriptan's potential to modify human aggression in a laboratory paradigm across a range of alcohol doses. Alcohol has been consistently associated with aggression and violence, thus we hoped to expand current understanding of alcohol's role in aggressive behavior via manipulation of the serotonin (5-HT) system. METHODS Eleven social drinkers, seven male, were recruited to participate in a research study lasting 3-4 weeks. Aggression was measured using the point-subtraction aggression paradigm (PSAP), a laboratory model widely used in human aggression studies. Subjects were administered 5-mg zolmitriptan and placebo capsules along with alcohol doses of 0.0, 0.4 and 0.8 g/kg in a within-subject, counterbalanced dosing design. Data were analyzed as the ratio of aggressive/monetary-earning responses, to account for possible changes in overall motor function due to alcohol. RESULTS There was a significant alcohol by zolmitriptan interaction on the aggressive/monetary response ratio. Specifically, compared to placebo, zolmitriptan decreased the aggressive/monetary ratio at the 0.4- and 0.8-g/kg alcohol doses. CONCLUSIONS A 5-mg dose of zolmitriptan effectively reduced alcohol-related aggression in an acute dosing protocol, demonstrating an interaction of 5-HT and alcohol in human aggressive behavior.
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Affiliation(s)
- Joshua L Gowin
- Department of Psychiatry and Behavioral Sciences, The University of Texas Health Science Center Houston, Houston, TX, USA
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169
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McCracken LM, McCracken ML, Gong DH, Trudell JR, Harris RA. Linking of Glycine Receptor Transmembrane Segments Three and Four Allows Assignment of Intrasubunit-Facing Residues. ACS Chem Neurosci 2010; 1:482. [PMID: 21326622 DOI: 10.1021/cn100019g] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Glycine receptors (GlyRs) are pentameric ligand-gated ion channels that mediate inhibitory neurotransmission in the brain and spinal cord and are targets of alcohols and anesthetics. The transmembrane (TM) domain of GlyR subunits is composed of four α-helical segments (TM1-4), but there are conflicting data about the orientation of TM3 and TM4 and, therefore, also the proximity of residues (e.g., A288) that are important for alcohol and anesthetic effects. In the present study, we investigated the proximity of A288 in TM3 to residues in TM4 from M404 to K411. We generated eight double mutant GlyRs (A288C/M404C, A288C/F405C, A288C/Y406C, A288C/W407C, A288C/I408C, A288C/I409C, A288C/Y410C, and A288C/K411C), as well as the corresponding single mutants, and expressed them in Xenopus laevis oocytes. To measure glycine responses, we used two-electrode voltage clamp electrophysiology. We built homology models of the GlyR using structures of the nicotinic acetylcholine receptor (nAChR) and a prokaryotic ion channel (Gloeobacter violaceus, GLIC) as templates, and asked which model best fit our experimental data. Application of the cross-linking reagent HgCl(2) in the closed state produced a leftward shift in the glycine concentration-response curves of the A288C/W407C and A288C/Y410C mutants, suggesting they are able to form cross-links. In addition, when HgCl(2) was coapplied with glycine, responses were changed in the A288C/Y406C, A288C/I409C, and A288C/Y410C double mutants, suggesting that agonist-induced rotation of TM4 allows A288C/Y406C and A288C/I409C to cross-link. These results are consistent with a model of GlyR, based on nAChR, in which A288, Y406, W407, I409, and Y410 face into a four-helical bundle.
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Affiliation(s)
- L. M. McCracken
- Waggoner Center for Alcohol & Addiction Research, University of Texas at Austin, Austin, Texas
| | - M. L. McCracken
- Waggoner Center for Alcohol & Addiction Research, University of Texas at Austin, Austin, Texas
| | - D. H. Gong
- Waggoner Center for Alcohol & Addiction Research, University of Texas at Austin, Austin, Texas
| | - J. R. Trudell
- Department of Anesthesia and Beckman Program for Molecular and Genetic Medicine, Stanford School of Medicine, Stanford, California 94305-5117
| | - R. A. Harris
- Waggoner Center for Alcohol & Addiction Research, University of Texas at Austin, Austin, Texas
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170
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Pickering C, Chau PP, Söderpalm B, Ericson M. Ethanol and phencyclidine interact with respect to nucleus accumbens dopamine release: differential effects of administration order and pretreatment protocol. Front Behav Neurosci 2010; 4:32. [PMID: 20589092 PMCID: PMC2892999 DOI: 10.3389/fnbeh.2010.00032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 05/17/2010] [Indexed: 11/13/2022] Open
Abstract
Executive dysfunction is a common symptom among alcohol-dependent individuals. Phencyclidine (PCP) injection induces dysfunction in the prefrontal cortex of animals but little is known about how PCP affects the response to ethanol. Using the in vivo microdialysis technique in male Wistar rats, we investigated how systemic injection of 5 mg/kg PCP would affect the dopamine release induced by local infusion of 300 mM ethanol into the nucleus accumbens. PCP given 60 min before ethanol entirely blocked ethanol-induced dopamine release. However, when ethanol was administered 60 min before PCP, both drugs induced dopamine release and PCP's effect was potentiated by ethanol (180% increase vs 150%). To test the role of prefrontal cortex dysfunction in ethanol reinforcement, animals were pretreated for 5 days with 2.58 mg/kg PCP according to previously used 'PFC hypofunction protocols'. This, however, did not change the relative response to PCP or ethanol compared to saline-treated controls. qPCR illustrated that this low PCP dose did not significantly change expression of glucose transporters Glut1 (SLC2A1) or Glut3 (SLC2A3), monocarboxylate transporter MCT2 (SLC16A7), glutamate transporters GLT-1 (SLC1A2) or GLAST (SLC1A3), the immediate early gene Arc (Arg3.1) or GABAergic neuron markers GAT-1 (SLC6A1) and parvalbumin. Therefore, we concluded that PCP at a dose of 2.58 mg/kg for 5 days did not induce hypofunction in Wistar rats. However, PCP and ethanol do have overlapping mechanisms of action and these drugs differentially affect mesolimbic dopaminergic transmission depending on the order of administration.
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Affiliation(s)
- Chris Pickering
- Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, University of GothenburgGothenburg, Sweden
| | - Pei Pei Chau
- Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, University of GothenburgGothenburg, Sweden
| | - Bo Söderpalm
- Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, University of GothenburgGothenburg, Sweden
- Beroendekliniken, Sahlgrenska University HospitalGothenburg, Sweden
| | - Mia Ericson
- Addiction Biology Unit, Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, University of GothenburgGothenburg, Sweden
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171
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Nam HW, Lee MR, Hinton DJ, Choi DS. Reduced effect of NMDA glutamate receptor antagonist on ethanol-induced ataxia and striatal glutamate levels in mice lacking ENT1. Neurosci Lett 2010; 479:277-81. [PMID: 20570605 DOI: 10.1016/j.neulet.2010.05.079] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 05/25/2010] [Indexed: 12/26/2022]
Abstract
Alcohol-sensitive type 1 equilibrative nucleotide transporter (ENT1) is known to regulate glutamate signaling in the striatum as well as ethanol intoxication. However, it was unclear whether altered extracellular glutamate levels in ENT1(-/-) mice contribute to ethanol-induced behavioral changes. Here we report that altered glutamate signaling in ENT1(-/-) mice is implicated in the ethanol-induced locomotion and ataxia by NMDA receptor antagonist, CGP37849. ENT1(-/-) mice appear less intoxicated following sequential treatment with CGP37849 and ethanol, compared to ENT1(+/+) littermates on the rotarod. These results indicate that inhibiting NMDA glutamate receptors is critical to regulate the response and susceptibility of alcohol related behaviors. Interestingly, a microdialysis experiment showed that the ventral striatum of ENT1(-/-) mice is less sensitive to the glutamate-reducing effect of the NMDA receptor antagonist compared to the dorsal striatum. Our findings suggest that differential glutamate neurotransmission in the striatum regulates ethanol intoxication.
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Affiliation(s)
- Hyung Wook Nam
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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172
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Gomez M, Raju SV, Viswanathan A, Painter RG, Bonvillain R, Byrne P, Nguyen DH, Bagby GJ, Kolls JK, Nelson S, Wang G. Ethanol upregulates glucocorticoid-induced leucine zipper expression and modulates cellular inflammatory responses in lung epithelial cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2010; 184:5715-22. [PMID: 20382889 PMCID: PMC2901557 DOI: 10.4049/jimmunol.0903521] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Alcohol abuse is associated with immunosuppressive and infectious sequelae. Particularly, alcoholics are more susceptible to pulmonary infections. In this report, gene transcriptional profiles of primary human airway epithelial cells exposed to varying doses of alcohol (0, 50, and 100 mM) were obtained. Comparison of gene transcription levels in 0 mM alcohol treatments with those in 50 mM alcohol treatments resulted in 2 genes being upregulated and 16 genes downregulated by at least 2-fold. Moreover, 0 mM and 100 mM alcohol exposure led to the upregulation of 14 genes and downregulation of 157 genes. Among the upregulated genes, glucocorticoid-induced leucine zipper (GILZ) responded to alcohol in a dose-dependent manner. Moreover, GILZ protein levels also correlated with this transcriptional pattern. Lentiviral expression of GILZ small interfering RNA in human airway epithelial cells diminished the alcohol-induced upregulation, confirming that GILZ is indeed an alcohol-responsive gene. Gene silencing of GILZ in A549 cells resulted in secretion of significantly higher amounts of inflammatory cytokines in response to IL-1beta stimulation. The GILZ-silenced cells were more resistant to alcohol-mediated suppression of cytokine secretion. Further data demonstrated that the glucocorticoid receptor is involved in the regulation of GILZ by alcohol. Because GILZ is a key glucocorticoid-responsive factor mediating the anti-inflammatory and immunosuppressive actions of steroids, we propose that similar signaling pathways may play a role in the anti-inflammatory and immunosuppressive effects of alcohol.
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Affiliation(s)
- Marla Gomez
- Alcohol Research Center and Gene Therapy Program, Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Sammeta V. Raju
- Alcohol Research Center and Gene Therapy Program, Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Anand Viswanathan
- Alcohol Research Center and Gene Therapy Program, Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Richard G. Painter
- Alcohol Research Center and Gene Therapy Program, Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Ryan Bonvillain
- Alcohol Research Center and Gene Therapy Program, Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Patrick Byrne
- Alcohol Research Center and Gene Therapy Program, Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Doan H. Nguyen
- Alcohol Research Center and Gene Therapy Program, Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Gregory J. Bagby
- Alcohol Research Center and Gene Therapy Program, Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Jay K. Kolls
- Alcohol Research Center and Gene Therapy Program, Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Steve Nelson
- Alcohol Research Center and Gene Therapy Program, Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Guoshun Wang
- Alcohol Research Center and Gene Therapy Program, Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
- Alcohol Research Center and Gene Therapy Program, Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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173
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Abstract
Molecular neurobiological studies have yielded enormous amounts of valuable information about neuronal response mechanisms and their adaptive changes. However, in relation to addiction this information is of limited value because almost every cell function appears to be involved. Thus it tells us only that neurons adapt to 'addictive drugs' as they do to all sorts of other functional disturbances. This information may be of limited help in the development of potential auxiliary agents for treatment of addiction. However, a reductionist approach which attempts to analyse addiction at ever finer levels of structure and function, is inherently incapable of explaining what causes these mechanisms to be brought into play in some cases and not in others, or by self-administration of a drug but not by passive exposure. There is abundant evidence that psychological, social, economic and specific situational factors play important roles in initiating addiction, in addition to genetic and other biological factors. Therefore, if we hope to be able to make predictions at any but a statistical level, or to develop effective means of prevention, it is necessary to devise appropriate integrative approaches to the study of addiction, rather than pursue an ever-finer reductive approach which leads steadily farther away from the complex interaction of drug, user, environment and specific situations that characterizes the problem in humans.
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Affiliation(s)
- Harold Kalant
- Department of Pharmacology, University of Toronto, Toronto, Canada.
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174
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Molecular targets and mechanisms for ethanol action in glycine receptors. Pharmacol Ther 2010; 127:53-65. [PMID: 20399807 DOI: 10.1016/j.pharmthera.2010.03.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 03/23/2010] [Indexed: 11/23/2022]
Abstract
Glycine receptors (GlyRs) are recognized as the primary mediators of neuronal inhibition in the spinal cord, brain stem and higher brain regions known to be sensitive to ethanol. Building evidence supports the notion that ethanol acting on GlyRs causes at least a subset of its behavioral effects and may be involved in modulating ethanol intake. For over two decades, GlyRs have been studied at the molecular level as targets for ethanol action. Despite the advances in understanding the effects of ethanol in vivo and in vitro, the precise molecular sites and mechanisms of action for ethanol in ligand-gated ion channels in general, and in GlyRs specifically, are just now starting to become understood. The present review focuses on advances in our knowledge produced by using molecular biology, pressure antagonism, electrophysiology and molecular modeling strategies over the last two decades to probe, identify and model the initial molecular sites and mechanisms of ethanol action in GlyRs. The molecular targets on the GlyR are covered on a global perspective, which includes the intracellular, transmembrane and extracellular domains. The latter has received increasing attention in recent years. Recent molecular models of the sites of ethanol action in GlyRs and their implications to our understanding of possible mechanism of ethanol action and novel targets for drug development in GlyRs are discussed.
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175
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Bhattacharji A, Klett N, Go RCV, Covarrubias M. Inhalational anaesthetics and n-alcohols share a site of action in the neuronal Shaw2 Kv channel. Br J Pharmacol 2010; 159:1475-85. [PMID: 20136839 DOI: 10.1111/j.1476-5381.2010.00642.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Neuronal ion channels are key targets of general anaesthetics and alcohol, and binding of these drugs to pre-existing and relatively specific sites is thought to alter channel gating. However, the underlying molecular mechanisms of this action are still poorly understood. Here, we investigated the neuronal Shaw2 voltage-gated K(+) (K(v)) channel to ask whether the inhalational anaesthetic halothane and n-alcohols share a binding site near the activation gate of the channel. EXPERIMENTAL APPROACH Focusing on activation gate mutations that affect channel modulation by n-alcohols, we investigated n-alcohol-sensitive and n-alcohol-resistant K(v) channels heterologously expressed in Xenopus oocytes to probe the functional modulation by externally applied halothane using two-electrode voltage clamping and a gas-tight perfusion system. KEY RESULTS Shaw2 K(v) channels are reversibly inhibited by halothane in a dose-dependent and saturable manner (K(0.5)= 400 microM; n(H)= 1.2). Also, discrete mutations in the channel's S4S5 linker are sufficient to reduce or confer inhibition by halothane (Shaw2-T330L and K(v)3.4-G371I/T378A respectively). Furthermore, a point mutation in the S6 segment of Shaw2 (P410A) converted the halothane-induced inhibition into halothane-induced potentiation. Lastly, the inhibition resulting from the co-application of n-butanol and halothane is consistent with the presence of overlapping binding sites for these drugs and weak binding cooperativity. CONCLUSIONS AND IMPLICATIONS These observations strongly support a molecular model of a general anaesthetic binding site in the Shaw2 K(v) channel. This site may involve the amphiphilic interface between the S4S5 linker and the S6 segment, which plays a pivotal role in K(v) channel activation.
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Affiliation(s)
- Aditya Bhattacharji
- Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA, USA
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176
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Embryonic exposure to ethanol disturbs regulation of mitotic spindle orientation via GABA(A) receptors in neural progenitors in ventricular zone of developing neocortex. Neurosci Lett 2010; 472:128-32. [PMID: 20138119 DOI: 10.1016/j.neulet.2010.01.071] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 01/12/2010] [Accepted: 01/27/2010] [Indexed: 11/20/2022]
Abstract
Neural progenitors in the ventricular zone of the developing neocortex divide oriented either parallel or perpendicular to the ventricular surface based on their mitotic spindle orientation. It has been shown that the cleavage plane orientation is developmentally regulated and plays a crucial role in cell fate determination of neural progenitors or the maintenance of the proliferative ventricular zone during neocortical development. We tested if fetal exposure to ethanol, the most widely used psychoactive agent and a potent teratogen that may cause malformation in the central nervous system, alters mitotic cleavage orientation of the neural progenitors at the apical surface of the ventricular zone in the developing neocortex. Fetal exposure to ethanol on E10.5 and 11.5 increased the occurrence frequency of a horizontal cleavage plane that is parallel to the ventricular surface on E 12.5. Administration of picrotoxin, a GABA(A) receptor antagonist, prior to ethanol administration canceled the effect of ethanol with the frequency of horizontal division similar to the control level, although picrotoxin itself did not show any effect on cleavage plane orientation. Phenobarbital, a GABA(A) receptor agonist, induced horizontal cleavage to an extent similar to that induced by ethanol administration. (+)MK801, an antagonist of NMDA receptor that is another major target of ethanol in neural cells, did not affect the cleavage plane of dividing progenitors. These results suggest that fetal ethanol exposure induced alterations in the cleavage plane orientation of neural progenitors in the ventricular zone of the neocortex via the enhancement of the function of GABA(A) receptors.
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177
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Björk K, Hansson AC, Sommer WH. Genetic Variation and Brain Gene Expression in Rodent Models of Alcoholism. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2010; 91:129-71. [DOI: 10.1016/s0074-7742(10)91005-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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178
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Sullivan EV, Harris RA, Pfefferbaum A. Alcohol's effects on brain and behavior. ALCOHOL RESEARCH & HEALTH : THE JOURNAL OF THE NATIONAL INSTITUTE ON ALCOHOL ABUSE AND ALCOHOLISM 2010; 33:127-43. [PMID: 23579943 PMCID: PMC3625995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Over the past 40 years, rigorous examination of brain function, structure, and attending factors through multidisciplinary research has helped identify the substrates of alcohol-related damage in the brain. One main area of this research has focused on the neuropsychological sequelae of alcoholism, which has resulted in the description of a pattern of sparing and impairment that provided an essential understanding of the functional deficits as well as of spared capabilities that could be useful in recovery. These studies have elucidated the component processes of memory, problem solving, and cognitive control, as well as visuospatial, and motor processes and their interactions with cognitive control processes. Another large area of research has focused on observable brain pathology, using increasingly sophisticated imaging technologies--progressing from pneumoencephalography to computed tomography, magnetic resonance imaging (MRI), diffusion tensor imaging, and functional MRI--that have enabled ever more detailed insight into brain structure and function. These advancements also have allowed analysis of the course of brain structural changes through periods of drinking, abstinence, and relapse.
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Affiliation(s)
- Edith V Sullivan
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California
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179
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Moonat S, Starkman BG, Sakharkar A, Pandey SC. Neuroscience of alcoholism: molecular and cellular mechanisms. Cell Mol Life Sci 2010; 67:73-88. [PMID: 19756388 PMCID: PMC3747955 DOI: 10.1007/s00018-009-0135-y] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 07/28/2009] [Accepted: 08/13/2009] [Indexed: 01/21/2023]
Abstract
Alcohol use and abuse appear to be related to neuroadaptive changes at functional, neurochemical, and structural levels. Acute and chronic ethanol exposure have been shown to modulate function of the activity-dependent gene transcription factor, cAMP-responsive element binding (CREB) protein in the brain, which may be associated with the development of alcoholism. Study of the downstream effectors of CREB have identified several important CREB-related genes, such as neuropeptide Y, brain-derived neurotrophic factor, activity-regulated cytoskeleton-associated protein, and corticotrophin-releasing factor, that may play a crucial role in the behavioral effects of ethanol and molecular changes in the specific neurocircuitry that underlie both alcohol addiction and a genetic predisposition to alcoholism. Brain chromatin remodeling due to histone covalent modifications may also be involved in mediating the behavioral effects and neuroadaptive changes that occur during ethanol exposure. This review outlines progressive neuroscience research into molecular and epigenetic mechanisms of alcoholism.
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Affiliation(s)
- Sachin Moonat
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL USA
- Jesse Brown VA Medical Center, Chicago, IL USA
| | - Bela G. Starkman
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL USA
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL USA
- Jesse Brown VA Medical Center, Chicago, IL USA
| | - Amul Sakharkar
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL USA
- Jesse Brown VA Medical Center, Chicago, IL USA
| | - Subhash C. Pandey
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL USA
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL USA
- Jesse Brown VA Medical Center, Chicago, IL USA
- Department of Psychiatry, University of Illinois at Chicago and Jesse Brown VA Medical Center, 820 S. Damen Avenue (M/C 151), Chicago, IL 60612 USA
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180
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Flory GS, O'Malley J, Grant KA, Park B, Kroenke CD. Quantification of ethanol methyl (1)H magnetic resonance signal intensity following intravenous ethanol administration in primate brain. Methods 2009; 50:189-98. [PMID: 20018244 DOI: 10.1016/j.ymeth.2009.12.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 12/08/2009] [Accepted: 12/09/2009] [Indexed: 11/19/2022] Open
Abstract
In vivo(1)H magnetic resonance spectroscopy (MRS) can be used to directly monitor brain ethanol. Previously, studies of human subjects have lead to the suggestion that the ethanol methyl (1)H MRS signal intensity relates to tolerance to ethanol's intoxicating effects. More recently, the ethanol (1)H MRS signal intensity has been recognized to vary between brain gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) due to differences in T(2) within these environments. The methods presented here extend ethanol MRS techniques to non-human primate subjects. Twelve monkeys were administered ethanol while sedated and positioned within a 3T MRI system. Chemical shift imaging (CSI) measurements were performed following intravenous infusion of 1g/kg ethanol. Magnetic resonance imaging (MRI) data were also recorded for each monkey to provide volume fractions of GM, WM, and CSF for each CSI spectrum. To estimate co-variance of ethanol MRS intensity with GM, WM, and CSF volume fractions, the relative contribution of each tissue subtype was determined following corrections for radiofrequency pulse profile non-uniformity, chemical shift artifacts, and differences between the point spread function in the CSI data and the imaging data. The ethanol MRS intensity per unit blood ethanol concentration was found to differ between GM, WM, and CSF. Individual differences in MRS intensity were larger in GM than WM. This methodology demonstrates the feasibility of ethanol MRS experiments and analysis in non-human primate subjects, and suggests GM may be a site of significant variation in ethanol MRS intensity between individuals.
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Affiliation(s)
- Graham S Flory
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, USA
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181
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Mill CP, Chester JA, Riese DJ. EGFR may couple moderate alcohol consumption to increased breast cancer risk. BREAST CANCER-TARGETS AND THERAPY 2009; 1:31-8. [PMID: 24367161 DOI: 10.2147/bctt.s6254] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Alcohol consumption is an established risk factor for breast cancer. Nonetheless, the mechanism by which alcohol contributes to breast tumor initiation or progression has yet to be definitively established. Studies using cultured human tumor cell lines have identified signaling molecules that may contribute to the effects of alcohol, including reactive oxygen species and other ethanol metabolites, matrix metalloproteases, the ErbB2/Her2/Neu receptor tyrosine kinase, cytoplasmic protein kinases, adenylate cyclase, E-cadherins, estrogen receptor, and a variety of transcription factors. Emerging data suggest that the epidermal growth factor receptor (EGFR) tyrosine kinase may contribute to breast cancer genesis and progression. Here we integrate these findings and propose three mechanisms by which alcohol contributes to breast cancer. A common feature of these mechanisms is increased EGFR signaling. Finally, we discuss how these mechanisms suggest strategies for addressing the risks associated with alcohol consumption.
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Affiliation(s)
- Christopher P Mill
- Purdue University School of Pharmacy, Purdue University Center for Cancer Research, West Lafayette, IN, USA
| | - Julia A Chester
- Purdue University Department of Psychological Sciences, West Lafayette, IN, USA
| | - David J Riese
- Purdue University School of Pharmacy, Purdue University Center for Cancer Research, West Lafayette, IN, USA
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182
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Aryal P, Dvir H, Choe S, Slesinger PA. A discrete alcohol pocket involved in GIRK channel activation. Nat Neurosci 2009; 12:988-95. [PMID: 19561601 PMCID: PMC2717173 DOI: 10.1038/nn.2358] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 06/03/2009] [Indexed: 12/18/2022]
Abstract
Ethanol modifies neural activity in the brain by modulating ion channels. Ethanol activates G protein-gated inwardly rectifying K+ channels, but the molecular mechanism is not well understood. Here, we used a crystal structure of a mouse inward rectifier containing a bound alcohol and structure-based mutagenesis to probe a putative alcohol-binding pocket located in the cytoplasmic domains of GIRK channels. Substitutions with bulkier side-chains in the alcohol-binding pocket reduced or eliminated activation by alcohols. By contrast, alcohols inhibited constitutively open channels, such as IRK1 or GIRK2 that binds PIP2 strongly. Mutations in the hydrophobic alcohol-binding pocket of these channels had no effect on alcohol-dependent inhibition, suggesting an alternate site is involved in inhibition. Comparison of high-resolution structures of inwardly rectifying K+ channels suggests a model for activation of GIRK channels utilizing this hydrophobic alcohol-binding pocket. These results provide a tool for developing therapeutic compounds that could mitigate the effects of alcohol.
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Affiliation(s)
- Prafulla Aryal
- Peptide Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, USA
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183
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Palfreyman MT. With Happyhour, everyone's under the table. Cell 2009; 137:802-4. [PMID: 19490888 DOI: 10.1016/j.cell.2009.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The molecular and cellular targets that mediate alcohol intoxication are poorly understood. In this issue, Corl et al. (2009) now implicate a new Ste20 family kinase (Happyhour) and the EGFR/ERK signaling pathway it antagonizes in alcohol intoxication in flies.
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184
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Irons TD, MacPhail RC, Hunter DL, Padilla S. Acute neuroactive drug exposures alter locomotor activity in larval zebrafish. Neurotoxicol Teratol 2009; 32:84-90. [PMID: 19465114 DOI: 10.1016/j.ntt.2009.04.066] [Citation(s) in RCA: 207] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 03/15/2009] [Accepted: 04/23/2009] [Indexed: 11/25/2022]
Abstract
As part of the development of a rapid in vivo screen for prioritization of toxic chemicals, we have begun to characterize the locomotor activity of zebrafish (Danio rerio) larvae by assessing the acute effects of prototypic drugs that act on the central nervous system. Initially, we chose ethanol, d-amphetamine, and cocaine, which are known, in mammals, to increase locomotion at low doses and decrease locomotion at higher doses. Wild-type larvae were individually maintained in 96-well microtiter plates at 26 degrees C, under a 14:10 h light:dark cycle, with lights on at 0830 h. At 6 days post-fertilization, ethanol (1-4% v/v), d-amphetamine sulfate (0.1-20.0 microM) or cocaine hydrochloride (0.2-50.0 microM) were administered to the larvae by immersion. Beginning 20 min into the exposure, locomotion was assessed for each animal for 70 min using 10-minute, alternating light (visible light) and dark (infrared light) periods. Low concentrations of ethanol and d-amphetamine increased activity, while higher concentrations of all three drugs decreased activity. Because ethanol effects occurred predominately during the light periods, whereas the d-amphetamine and cocaine effects occurred during the dark periods, alternating lighting conditions proved to be advantageous. These results indicate that zebrafish larvae are sensitive to neuroactive drugs, and their locomotor response is similar to that of mammals.
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Affiliation(s)
- T D Irons
- Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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185
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Dopico AM, Lovinger DM. Acute alcohol action and desensitization of ligand-gated ion channels. Pharmacol Rev 2009; 61:98-114. [PMID: 19270242 DOI: 10.1124/pr.108.000430] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ethanol exerts its biological actions through multiple receptors, including ion channels. Ion channels that are sensitive to pharmacologically relevant ethanol concentrations constitute a heterogeneous set, including structurally unrelated proteins solely sharing the property that their gating is regulated by a ligand(s). Receptor desensitization is almost universal among these channels, and its modulation by ethanol may be a crucial aspect of alcohol pharmacology and effects in the body. We review the evidence documenting interactions between ethanol and ionotropic receptor desensitization, and the contribution of this interaction to overall ethanol action on channel function. In some cases, such as type 3 serotonin, nicotinic acetylcholine, GABA-A, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors, ethanol actions on apparent desensitization play a significant role in acute drug action on receptor function. In a few cases, mutagenesis helped to identify different areas within a receptor protein that differentially sense n-alcohols, resulting in differential modulation of receptor desensitization. However, desensitization of a receptor is linked to a variety of biochemical processes that may alter protein conformation, such as the lipid microenvironment, post-translational channel modification, and channel subunit composition, the relative contribution of these processes to ethanol interactions with channel desensitization remains unclear. Understanding interactions between ethanol and ionotropic receptor desensitization may help to explain different ethanol actions 1) when ethanol is evaluated in vitro on cloned channel proteins, 2) under physiological or pathological conditions or in distinct cell domains with modified ligand concentration and/or receptor conformation. Finally, receptor desensitization is likely to participate in molecular and, possibly, behavioral tolerance to ethanol, which is thought to contribute to the risk of alcoholism.
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Affiliation(s)
- Alex M Dopico
- Department of Pharmacology, University of Tennessee Health Science Center, 874 Union Avenue, Memphis, TN 38163-0001, USA.
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186
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Beckstead MJ, Phillips TJ. Mice selectively bred for high- or low-alcohol-induced locomotion exhibit differences in dopamine neuron function. J Pharmacol Exp Ther 2009; 329:342-9. [PMID: 19122113 DOI: 10.1124/jpet.108.146316] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Elevated sensitivity to the euphoric or stimulant effects of ethanol is associated with higher levels of alcohol use in some human populations. Midbrain dopamine neurons are thought to be important mediators of both ethanol reward and locomotor stimulation. Patch-clamp recordings were used to examine the electrical properties of dopamine neurons in a genetic model of heightened (FAST) and reduced (SLOW) sensitivity to the locomotor-activating effects of ethanol. Pacemaker firing of dopamine neurons was faster in FAST than SLOW mice, as was the current density through I(H) channels. Acute administration of ethanol accelerated the firing of dopamine neurons to a greater extent in recordings from FAST than SLOW mice. Dopamine neurons from FAST mice also exhibited reduced GABA(A) receptor-mediated synaptic input, compared with SLOW mice. The results suggest that dopamine neuron I(H) channels, firing rate, and GABAergic input may play a role in sensitivity to the locomotor activation observed at early time points after ethanol administration and could underlie differences in sensitivity to alcohol relevant to risk for alcohol abuse.
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Affiliation(s)
- Michael J Beckstead
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon, USA.
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187
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Mustard JA, Edgar EA, Mazade RE, Wu C, Lillvis JL, Wright GA. Acute ethanol ingestion impairs appetitive olfactory learning and odor discrimination in the honey bee. Neurobiol Learn Mem 2008; 90:633-43. [PMID: 18723103 DOI: 10.1016/j.nlm.2008.07.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 07/29/2008] [Accepted: 07/29/2008] [Indexed: 11/30/2022]
Abstract
Invertebrates are valuable models for increasing our understanding of the effects of ethanol on the nervous system, but most studies on invertebrates and ethanol have focused on the effects of ethanol on locomotor behavior. In this work we investigate the influence of an acute dose of ethanol on appetitive olfactory learning in the honey bee (Apis mellifera), a model system for learning and memory. Adult worker honey bees were fed a range of doses (2.5%, 5%, 10%, or 25%) of ethanol and then conditioned to associate an odor with a sucrose reward using either a simple or differential conditioning paradigm. Consumption of ethanol before conditioning significantly reduced both the rate of acquisition and the asymptotic strength of the association. Honey bees also exhibited a dose dependent reduction in arousal/attention during conditioning. Consumption of ethanol after conditioning did not affect recall 24h later. The observed deficits in acquisition were not due to the affect of ethanol on gustatory sensitivity or motor function. However, honey bees given higher doses of ethanol had difficulty discriminating amongst different odors suggesting that ethanol consumption influences olfactory processing. Taken together, these results demonstrate that an acute dose of ethanol affects appetitive learning and olfactory perception in the honey bee.
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Affiliation(s)
- Julie A Mustard
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287, USA.
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188
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Foley JF, VanHook AM. Science Signaling
Podcast: 15 July 2008. Sci Signal 2008. [DOI: 10.1126/scisignal.128pc6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
This conversation is about research highlighted in the Editors' Choice summary titled, "Macrophages Go Back to School." The highlighted articles are T. Hagemann, T. Lawrence, I. McNeish, K. A. Charles, H. Kulbe, R. G. Thompson, S. C. Robinson, F. R. Balkwill, "Re-educating" tumor-associated macrophages by targeting NF-κB.
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, 1261-1268 (2008), and C. H. Y. Fong, M. Bebien, A. Didierlaurent, R. Nebauer, T. Hussell, D. Broide, M. Karin, T. Lawrence, An antiinflammatory role for IKKβ through the inhibition of "classical" macrophage activation.
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, 1269-1276 (2008). (Length: 11 min; file size: 5.00 MB; file format: mp3; location:
http://podcasts.aaas.org/science_signaling/ScienceSignaling_080715.mp3
)
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Affiliation(s)
- John F. Foley
- Associate Editor of Science Signaling, American Association for the Advancement of Science, 1200 New York Avenue, N.W., Washington, DC 20005, USA
| | - Annalisa M. VanHook
- Associate Online Editor of Science Signaling, American Association for the Advancement of Science, 1200 New York Avenue, N.W., Washington, DC 20005, USA
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189
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Pietrzykowski AZ, Treistman SN. The molecular basis of tolerance. ALCOHOL RESEARCH & HEALTH : THE JOURNAL OF THE NATIONAL INSTITUTE ON ALCOHOL ABUSE AND ALCOHOLISM 2008; 31:298-309. [PMID: 23584007 PMCID: PMC3860466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Tolerance is defined as the diminished response to alcohol or other drugs over the course of repeated or prolonged exposure. This mechanism allows physiological processes to achieve stability in a constantly changing environment. The onset of tolerance may occur within minutes, during a single exposure to alcohol (i.e., acute tolerance), or over longer timeframes and with prolonged exposure to alcohol (i.e., rapid or chronic tolerance). Changes in tolerance induced by alcohol may affect several processes at the molecular, cellular, or behavioral level. These effects often are interrelated and may be difficult to separate. This article describes changes at the molecular level that are related to the onset of acute, rapid, or chronic tolerance. It focuses on neuronal membrane-bound channels and the factors that affect their function and production, such as modification of protein synthesis and activity, interaction with the membrane lipid microenvironment, epigenetic effects on cytoplasmic regulation, and gene transcription. Also considered is the genetics of tolerance.
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