In vivo and in vitro hyperbaric studies in mice suggest novel sites of action for ethanol

Daryl L. Davies; Michael B. Bolger; Roberta D. Brinton; Deborah A. Finn; Ronald L. Alkana

doi:10.1007/s002130050843

In vivo and in vitro hyperbaric studies in mice suggest novel sites of action for ethanol

Daryl L. Davies
, Michael B. Bolger
, Roberta D. Brinton
, Deborah A. Finn
, Ronald L. Alkana

Behavioral Neuroscience

Research output: Contribution to journal › Article › peer-review

14 Scopus citations

Abstract

The present study uses increased atmospheric pressure as an ethanol antagonist to test the hypothesis that allosteric coupling pathways in the GABA(A) receptor complex represent initial sites of action for ethanol. This was accomplished using behavioral and in vitro measures to determine the effects of pressure on ethanol and other GABAergic drags in C57BL/6 and LS mice. Behaviorally, exposure to 12 times normal atmospheric pressure (ATA) of a helium-oxygen gas mixture (heliox) antagonized loss of righting reflex (LORR) induced by the allosteric modulators ethanol and pentobarbital, but did not antagonize LORR induced by the direct GABA agonist 4,5,6,7- tetrahydroisoxazolo-pyridin-3-ol (THIP). Similarly, exposure to 12 ATA heliox antagonized the anticonvulsant effects verses isoniazid of ethanol, diazepam and pentobarbital. Biochemically, exposure to 12 ATA heliox antagonized potentiation of GABA-activated ³⁶Cl-uptake by ethanol, flunitrazepam and pentobarbital in LS mouse brain preparations, but did not alter GABA- activated ³⁶Cl-uptake per se. In contrast to its antagonist effect versus other allosteric modulators, pressure did not antagonize these behavioral or in vitro effects induced by the neuroactive steroid, 3α-hydroxy-5β-pregnan- 20-one (3α,5β-P). These findings add to evidence that pressure directly and selectively antagonizes drug effects mediated through allosteric coupling pathways. The results fit predictions, and thus support the hypothesis that allosteric coupling pathways in GABA(A) receptors represent initial sites of action for ethanol. Collectively, the results suggest that there may be common physicochemical and underlying structural characteristics that define ethanol sensitive regions of receptor proteins and/or their associated membranes that can be identified by pressure within (e.g., GABA(A)) and possibly across (e.g., GABA(A), NMDA, 5HT₃) receptors.

Original language	English (US)
Pages (from-to)	339-350
Number of pages	12
Journal	Psychopharmacology
Volume	141
Issue number	4
DOIs	https://doi.org/10.1007/s002130050843
State	Published - 1999

Funding

Devaud LL, Purdy RH, Morrow AL (1995) The neurosteroid, 3a - hydroxy-5a pregnan-20-one, protects against bicuculline-in- duced seizures during ethanol withdrawal in rats. Alcohol Clin Alcohol and Health (1993) Eighth Special Report to the US Con-Exp Res 19:350–355 gress on Alcohol and Health. NIAAA, US Department of Finn DA, Bejanian M, Jones BL, McGivern RF, Syapin PJ, Crab-Health and Human Service, Alexandria, Virginia be JC, Alkana RL (1990) Body temperature differentially af-Alkana RL, Malcolm RD (1980) Comparison of the effects of fects ethanol sensitivity in both inbred strains and selected acute alcohol intoxication on behavior in humans and other lines of mice. J Pharmacol Exp Ther 253:1229–1235 animals. In: Eriksson K, Sinclair JD, Kiianmaa K (eds) Ani-Franks NP, Lieb WR (1994) Molecular and cellular mechanisms mal models in alcohol research. Academic Press, London, pp of general anaesthesia. Nature 367:607–614 193–269 Franks NP, Lieb WR (1997) Anaesthetics set their sites on ion Alkana RL, Malcolm RD (1981) Low-level hyperbaric ethanol an-channels. Nature 389:334–335 tagonism in mice. Dose and pressure response. Pharmacology Gee KW, Bolger MB, Brinton RE, Coirini H, McEwen BS (1988) 22:199–208 Steroid modulation of the chloride ionophore in rat brain: Alkana RL, Malcolm RD (1982a) Hyperbaric ethanol antagonism structure-activity requirements, regional dependence and in mice: time course. Subst Alcohol Actions Misuse 3:41–46 mechanism of action. J Pharmacol Exp Ther 246:803–812 Alkana RL, Malcolm RD (1982b) Hyperbaric ethanol antagonism Halsey MJ (1982) Effects of high pressure on the central nervous in mice: studies on oxygen, nitrogen, strain and sex. Psycho-system. Physiol Rev 62:1341–1377 pharmacology 77:11–16 Harris RA, Allan AM (1985) Functional coupling of g -aminobu-Alkana RL, Boone DC, Finn DA (1985a) Temperature depen-tyric acid receptors to chloride channels in brain membranes. dence of ethanol depression: linear models in male and female Science 228:1108–1110 mice. Pharmacol Biochem Behav 23:309–316 Harris RA, Allan AM (1989a) Alcohol intoxication: ion channels Alkana RL, Finn DA, Galleisky GG, Syapin PJ, Malcolm RD and genetics. FASEB J 3:1689–1695 (1985b) Ethanol withdrawal in mice precipitated and exacer-Harris RA, Allan AM (1989b) Genetic differences in coupling of bated by hyperbaric exposure. Science 229:772–774 benzodiazepine receptors to chloride channels. Brain Res 490: Alkana RL, Syapin PJ, Galleisky GG, Finn DA (1987) Hyperbaric 26–32 exposure acts as an ethanol antagonist: evidence from chronic Harris RA, Brodie MS, Dunwiddie TV (1992) Possible substrates ethanol studies. Alcohol Alcohol [Suppl] 1:417–421 of ethanol reinforcement: GABA and dopamine. Ann NY Acad Alkana RL, Debold JF, Finn DA, Babbini M, Syapin PJ (1991a) Eth-Sci 654:61–69 anol-induced depression of aggression in mice antagonized by Janoff AS, Pringle MJ, Miller KW (1981) Correlation of general hyperbaric exposure. Pharmacol Biochem Behav 38:639–644 anesthetic potency with solubility in membranes. Biochim Alkana RL, Kobayashi LS, Jones BL, Finn DA, Syapin PJ (1991b) Biophys Acta 649:125–128 Low-level hyperbaric heliox does not affect drug-induced sei-Jones MV, Harrison NL (1993) Effects of volatile anesthetics on zure latency in mice. Ann NY Acad Sci 625:770–773 the kinetics of inhibitory postsynaptic currents in cultured rat Alkana RL, Finn DA, Jones BL, Kobayashi LS, Babbini M, Be-hippocampal neurons. J Neurophysiol 70:1339–1349 janian M, Syapin PJ (1992) Genetically determined differ-Kendig JJ (1984) Pressure dependence of excitable cell function. ences in the antagonistic effect of pressure on ethanol-induced Trends Neurol Sci 7:483–486 loss of righting reflex in mice. Alcohol Clin Exp Res 16:17–22 Korpi ER (1994) Role of GABAA receptors in the actions of alcohol Alkana RL, Davies DL, Morland J, Parker ES, Bejanian M (1995) and in alcoholism: recent advances. Alcohol Alcohol 29:115–129 Low level hyperbaric exposure antagonizes locomotor effects Little HJ (1996) How has molecular pharmacology contributed to of ethanol and n-propanol but not morphine in C57BL mice. our understanding of the mechanism(s) of general anesthesia? Alcohol Clin Exp Res 19:693–700 Pharmacol Ther 69:37–58 Allan AM, Harris RA (1986) g -aminobutyric acid and alcohol ac-Longoni B, Demontis GC, Olsen RW (1993) Enhancement of g - tions: neurochemical studies of long sleep and short sleep aminobutyric acidA receptor function and binding by volatile mice. Life Sci 39:2005–2015 anesthetic halothane. J Pharmacol Exp Ther 266:153–159 Acknowledgements The authors thank Dr. Nandita Pal, Ms. Christina de Luna, Ms. Tahira Mirza, Mr. Minh Ha and Mr. Khe-ang Long for their technical assistance. This work was supported by United States Public Health Service Research Grants RO1 AA03972, AA05234 and F31AA0436, National Institute on Alcohol Abuse and Alcoholism, NIH. This work was conducted as partial fulfilment of the requirements for the Ph.D. degree in Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California (D. L. D.).

Funders	Funder number
Author National Institutes of Health National Institutes of Health National Institutes of Health National Institutes of Health The Bev Hartig Huntington's Disease Foundation National Institutes of Health
National Institute of Alcohol Abuse and Alcoholism	R01AA003972
U.S. Public Health Service	F31AA0436, AA05234, RO1 AA03972

Keywords

3α-Hydroxy-5β-pregnan-20-one (3α, 5β-P)
4,5,6,7-Tetrahydroisoxazolo-pyridin-3-ol (THIP)
Allosteric coupling hypothesis
Anticonvulsant effect
Barbiturates
Benzodiazepines
C57BL/6 mice
Central nervous system
Ethanol antagonist
GABA(A) receptor complex
GABA-activated chloride ion uptake
Helium-oxygen gas mixture
Hyperbaric exposure
Ligand-gated ion channels
Loss of righting reflex (LORR)
N-Methyl-D-aspartate (NMDA)
Neuroactive steroid
γ-Aminobutryic acid (GABA)

ASJC Scopus subject areas

Pharmacology

Access to Document

10.1007/s002130050843

Cite this

@article{d41e1b36b7a24d3aa48d81eac5a673a8,

title = "In vivo and in vitro hyperbaric studies in mice suggest novel sites of action for ethanol",

abstract = "The present study uses increased atmospheric pressure as an ethanol antagonist to test the hypothesis that allosteric coupling pathways in the GABA(A) receptor complex represent initial sites of action for ethanol. This was accomplished using behavioral and in vitro measures to determine the effects of pressure on ethanol and other GABAergic drags in C57BL/6 and LS mice. Behaviorally, exposure to 12 times normal atmospheric pressure (ATA) of a helium-oxygen gas mixture (heliox) antagonized loss of righting reflex (LORR) induced by the allosteric modulators ethanol and pentobarbital, but did not antagonize LORR induced by the direct GABA agonist 4,5,6,7- tetrahydroisoxazolo-pyridin-3-ol (THIP). Similarly, exposure to 12 ATA heliox antagonized the anticonvulsant effects verses isoniazid of ethanol, diazepam and pentobarbital. Biochemically, exposure to 12 ATA heliox antagonized potentiation of GABA-activated 36Cl-uptake by ethanol, flunitrazepam and pentobarbital in LS mouse brain preparations, but did not alter GABA- activated 36Cl-uptake per se. In contrast to its antagonist effect versus other allosteric modulators, pressure did not antagonize these behavioral or in vitro effects induced by the neuroactive steroid, 3α-hydroxy-5β-pregnan- 20-one (3α,5β-P). These findings add to evidence that pressure directly and selectively antagonizes drug effects mediated through allosteric coupling pathways. The results fit predictions, and thus support the hypothesis that allosteric coupling pathways in GABA(A) receptors represent initial sites of action for ethanol. Collectively, the results suggest that there may be common physicochemical and underlying structural characteristics that define ethanol sensitive regions of receptor proteins and/or their associated membranes that can be identified by pressure within (e.g., GABA(A)) and possibly across (e.g., GABA(A), NMDA, 5HT3) receptors.",

keywords = "3α-Hydroxy-5β-pregnan-20-one (3α, 5β-P), 4,5,6,7-Tetrahydroisoxazolo-pyridin-3-ol (THIP), Allosteric coupling hypothesis, Anticonvulsant effect, Barbiturates, Benzodiazepines, C57BL/6 mice, Central nervous system, Ethanol antagonist, GABA(A) receptor complex, GABA-activated chloride ion uptake, Helium-oxygen gas mixture, Hyperbaric exposure, Ligand-gated ion channels, Loss of righting reflex (LORR), N-Methyl-D-aspartate (NMDA), Neuroactive steroid, γ-Aminobutryic acid (GABA)",

author = "Davies, \{Daryl L.\} and Bolger, \{Michael B.\} and Brinton, \{Roberta D.\} and Finn, \{Deborah A.\} and Alkana, \{Ronald L.\}",

note = "Funding Information: Devaud LL, Purdy RH, Morrow AL (1995) The neurosteroid, 3a - hydroxy-5a pregnan-20-one, protects against bicuculline-in- duced seizures during ethanol withdrawal in rats. Alcohol Clin Alcohol and Health (1993) Eighth Special Report to the US Con-Exp Res 19:350{\textendash}355 gress on Alcohol and Health. NIAAA, US Department of Finn DA, Bejanian M, Jones BL, McGivern RF, Syapin PJ, Crab-Health and Human Service, Alexandria, Virginia be JC, Alkana RL (1990) Body temperature differentially af-Alkana RL, Malcolm RD (1980) Comparison of the effects of fects ethanol sensitivity in both inbred strains and selected acute alcohol intoxication on behavior in humans and other lines of mice. J Pharmacol Exp Ther 253:1229{\textendash}1235 animals. In: Eriksson K, Sinclair JD, Kiianmaa K (eds) Ani-Franks NP, Lieb WR (1994) Molecular and cellular mechanisms mal models in alcohol research. Academic Press, London, pp of general anaesthesia. Nature 367:607{\textendash}614 193{\textendash}269 Franks NP, Lieb WR (1997) Anaesthetics set their sites on ion Alkana RL, Malcolm RD (1981) Low-level hyperbaric ethanol an-channels. Nature 389:334{\textendash}335 tagonism in mice. Dose and pressure response. Pharmacology Gee KW, Bolger MB, Brinton RE, Coirini H, McEwen BS (1988) 22:199{\textendash}208 Steroid modulation of the chloride ionophore in rat brain: Alkana RL, Malcolm RD (1982a) Hyperbaric ethanol antagonism structure-activity requirements, regional dependence and in mice: time course. Subst Alcohol Actions Misuse 3:41{\textendash}46 mechanism of action. J Pharmacol Exp Ther 246:803{\textendash}812 Alkana RL, Malcolm RD (1982b) Hyperbaric ethanol antagonism Halsey MJ (1982) Effects of high pressure on the central nervous in mice: studies on oxygen, nitrogen, strain and sex. Psycho-system. Physiol Rev 62:1341{\textendash}1377 pharmacology 77:11{\textendash}16 Harris RA, Allan AM (1985) Functional coupling of g -aminobu-Alkana RL, Boone DC, Finn DA (1985a) Temperature depen-tyric acid receptors to chloride channels in brain membranes. dence of ethanol depression: linear models in male and female Science 228:1108{\textendash}1110 mice. Pharmacol Biochem Behav 23:309{\textendash}316 Harris RA, Allan AM (1989a) Alcohol intoxication: ion channels Alkana RL, Finn DA, Galleisky GG, Syapin PJ, Malcolm RD and genetics. FASEB J 3:1689{\textendash}1695 (1985b) Ethanol withdrawal in mice precipitated and exacer-Harris RA, Allan AM (1989b) Genetic differences in coupling of bated by hyperbaric exposure. Science 229:772{\textendash}774 benzodiazepine receptors to chloride channels. Brain Res 490: Alkana RL, Syapin PJ, Galleisky GG, Finn DA (1987) Hyperbaric 26{\textendash}32 exposure acts as an ethanol antagonist: evidence from chronic Harris RA, Brodie MS, Dunwiddie TV (1992) Possible substrates ethanol studies. Alcohol Alcohol [Suppl] 1:417{\textendash}421 of ethanol reinforcement: GABA and dopamine. Ann NY Acad Alkana RL, Debold JF, Finn DA, Babbini M, Syapin PJ (1991a) Eth-Sci 654:61{\textendash}69 anol-induced depression of aggression in mice antagonized by Janoff AS, Pringle MJ, Miller KW (1981) Correlation of general hyperbaric exposure. Pharmacol Biochem Behav 38:639{\textendash}644 anesthetic potency with solubility in membranes. Biochim Alkana RL, Kobayashi LS, Jones BL, Finn DA, Syapin PJ (1991b) Biophys Acta 649:125{\textendash}128 Low-level hyperbaric heliox does not affect drug-induced sei-Jones MV, Harrison NL (1993) Effects of volatile anesthetics on zure latency in mice. Ann NY Acad Sci 625:770{\textendash}773 the kinetics of inhibitory postsynaptic currents in cultured rat Alkana RL, Finn DA, Jones BL, Kobayashi LS, Babbini M, Be-hippocampal neurons. J Neurophysiol 70:1339{\textendash}1349 janian M, Syapin PJ (1992) Genetically determined differ-Kendig JJ (1984) Pressure dependence of excitable cell function. ences in the antagonistic effect of pressure on ethanol-induced Trends Neurol Sci 7:483{\textendash}486 loss of righting reflex in mice. Alcohol Clin Exp Res 16:17{\textendash}22 Korpi ER (1994) Role of GABAA receptors in the actions of alcohol Alkana RL, Davies DL, Morland J, Parker ES, Bejanian M (1995) and in alcoholism: recent advances. Alcohol Alcohol 29:115{\textendash}129 Low level hyperbaric exposure antagonizes locomotor effects Little HJ (1996) How has molecular pharmacology contributed to of ethanol and n-propanol but not morphine in C57BL mice. our understanding of the mechanism(s) of general anesthesia? Alcohol Clin Exp Res 19:693{\textendash}700 Pharmacol Ther 69:37{\textendash}58 Allan AM, Harris RA (1986) g -aminobutyric acid and alcohol ac-Longoni B, Demontis GC, Olsen RW (1993) Enhancement of g - tions: neurochemical studies of long sleep and short sleep aminobutyric acidA receptor function and binding by volatile mice. Life Sci 39:2005{\textendash}2015 anesthetic halothane. J Pharmacol Exp Ther 266:153{\textendash}159 Acknowledgements The authors thank Dr. Nandita Pal, Ms. Christina de Luna, Ms. Tahira Mirza, Mr. Minh Ha and Mr. Khe-ang Long for their technical assistance. This work was supported by United States Public Health Service Research Grants RO1 AA03972, AA05234 and F31AA0436, National Institute on Alcohol Abuse and Alcoholism, NIH. This work was conducted as partial fulfilment of the requirements for the Ph.D. degree in Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California (D. L. D.).",

year = "1999",

doi = "10.1007/s002130050843",

language = "English (US)",

volume = "141",

pages = "339--350",

journal = "Psychopharmacology",

issn = "0033-3158",

publisher = "Springer Science and Business Media Deutschland GmbH",

number = "4",

}

TY - JOUR

T1 - In vivo and in vitro hyperbaric studies in mice suggest novel sites of action for ethanol

AU - Davies, Daryl L.

AU - Bolger, Michael B.

AU - Brinton, Roberta D.

AU - Finn, Deborah A.

AU - Alkana, Ronald L.

N1 - Funding Information: Devaud LL, Purdy RH, Morrow AL (1995) The neurosteroid, 3a - hydroxy-5a pregnan-20-one, protects against bicuculline-in- duced seizures during ethanol withdrawal in rats. Alcohol Clin Alcohol and Health (1993) Eighth Special Report to the US Con-Exp Res 19:350–355 gress on Alcohol and Health. NIAAA, US Department of Finn DA, Bejanian M, Jones BL, McGivern RF, Syapin PJ, Crab-Health and Human Service, Alexandria, Virginia be JC, Alkana RL (1990) Body temperature differentially af-Alkana RL, Malcolm RD (1980) Comparison of the effects of fects ethanol sensitivity in both inbred strains and selected acute alcohol intoxication on behavior in humans and other lines of mice. J Pharmacol Exp Ther 253:1229–1235 animals. In: Eriksson K, Sinclair JD, Kiianmaa K (eds) Ani-Franks NP, Lieb WR (1994) Molecular and cellular mechanisms mal models in alcohol research. Academic Press, London, pp of general anaesthesia. Nature 367:607–614 193–269 Franks NP, Lieb WR (1997) Anaesthetics set their sites on ion Alkana RL, Malcolm RD (1981) Low-level hyperbaric ethanol an-channels. Nature 389:334–335 tagonism in mice. Dose and pressure response. Pharmacology Gee KW, Bolger MB, Brinton RE, Coirini H, McEwen BS (1988) 22:199–208 Steroid modulation of the chloride ionophore in rat brain: Alkana RL, Malcolm RD (1982a) Hyperbaric ethanol antagonism structure-activity requirements, regional dependence and in mice: time course. Subst Alcohol Actions Misuse 3:41–46 mechanism of action. J Pharmacol Exp Ther 246:803–812 Alkana RL, Malcolm RD (1982b) Hyperbaric ethanol antagonism Halsey MJ (1982) Effects of high pressure on the central nervous in mice: studies on oxygen, nitrogen, strain and sex. Psycho-system. Physiol Rev 62:1341–1377 pharmacology 77:11–16 Harris RA, Allan AM (1985) Functional coupling of g -aminobu-Alkana RL, Boone DC, Finn DA (1985a) Temperature depen-tyric acid receptors to chloride channels in brain membranes. dence of ethanol depression: linear models in male and female Science 228:1108–1110 mice. Pharmacol Biochem Behav 23:309–316 Harris RA, Allan AM (1989a) Alcohol intoxication: ion channels Alkana RL, Finn DA, Galleisky GG, Syapin PJ, Malcolm RD and genetics. FASEB J 3:1689–1695 (1985b) Ethanol withdrawal in mice precipitated and exacer-Harris RA, Allan AM (1989b) Genetic differences in coupling of bated by hyperbaric exposure. Science 229:772–774 benzodiazepine receptors to chloride channels. Brain Res 490: Alkana RL, Syapin PJ, Galleisky GG, Finn DA (1987) Hyperbaric 26–32 exposure acts as an ethanol antagonist: evidence from chronic Harris RA, Brodie MS, Dunwiddie TV (1992) Possible substrates ethanol studies. Alcohol Alcohol [Suppl] 1:417–421 of ethanol reinforcement: GABA and dopamine. Ann NY Acad Alkana RL, Debold JF, Finn DA, Babbini M, Syapin PJ (1991a) Eth-Sci 654:61–69 anol-induced depression of aggression in mice antagonized by Janoff AS, Pringle MJ, Miller KW (1981) Correlation of general hyperbaric exposure. Pharmacol Biochem Behav 38:639–644 anesthetic potency with solubility in membranes. Biochim Alkana RL, Kobayashi LS, Jones BL, Finn DA, Syapin PJ (1991b) Biophys Acta 649:125–128 Low-level hyperbaric heliox does not affect drug-induced sei-Jones MV, Harrison NL (1993) Effects of volatile anesthetics on zure latency in mice. Ann NY Acad Sci 625:770–773 the kinetics of inhibitory postsynaptic currents in cultured rat Alkana RL, Finn DA, Jones BL, Kobayashi LS, Babbini M, Be-hippocampal neurons. J Neurophysiol 70:1339–1349 janian M, Syapin PJ (1992) Genetically determined differ-Kendig JJ (1984) Pressure dependence of excitable cell function. ences in the antagonistic effect of pressure on ethanol-induced Trends Neurol Sci 7:483–486 loss of righting reflex in mice. Alcohol Clin Exp Res 16:17–22 Korpi ER (1994) Role of GABAA receptors in the actions of alcohol Alkana RL, Davies DL, Morland J, Parker ES, Bejanian M (1995) and in alcoholism: recent advances. Alcohol Alcohol 29:115–129 Low level hyperbaric exposure antagonizes locomotor effects Little HJ (1996) How has molecular pharmacology contributed to of ethanol and n-propanol but not morphine in C57BL mice. our understanding of the mechanism(s) of general anesthesia? Alcohol Clin Exp Res 19:693–700 Pharmacol Ther 69:37–58 Allan AM, Harris RA (1986) g -aminobutyric acid and alcohol ac-Longoni B, Demontis GC, Olsen RW (1993) Enhancement of g - tions: neurochemical studies of long sleep and short sleep aminobutyric acidA receptor function and binding by volatile mice. Life Sci 39:2005–2015 anesthetic halothane. J Pharmacol Exp Ther 266:153–159 Acknowledgements The authors thank Dr. Nandita Pal, Ms. Christina de Luna, Ms. Tahira Mirza, Mr. Minh Ha and Mr. Khe-ang Long for their technical assistance. This work was supported by United States Public Health Service Research Grants RO1 AA03972, AA05234 and F31AA0436, National Institute on Alcohol Abuse and Alcoholism, NIH. This work was conducted as partial fulfilment of the requirements for the Ph.D. degree in Molecular Pharmacology and Toxicology, School of Pharmacy, University of Southern California (D. L. D.).

PY - 1999

Y1 - 1999

N2 - The present study uses increased atmospheric pressure as an ethanol antagonist to test the hypothesis that allosteric coupling pathways in the GABA(A) receptor complex represent initial sites of action for ethanol. This was accomplished using behavioral and in vitro measures to determine the effects of pressure on ethanol and other GABAergic drags in C57BL/6 and LS mice. Behaviorally, exposure to 12 times normal atmospheric pressure (ATA) of a helium-oxygen gas mixture (heliox) antagonized loss of righting reflex (LORR) induced by the allosteric modulators ethanol and pentobarbital, but did not antagonize LORR induced by the direct GABA agonist 4,5,6,7- tetrahydroisoxazolo-pyridin-3-ol (THIP). Similarly, exposure to 12 ATA heliox antagonized the anticonvulsant effects verses isoniazid of ethanol, diazepam and pentobarbital. Biochemically, exposure to 12 ATA heliox antagonized potentiation of GABA-activated 36Cl-uptake by ethanol, flunitrazepam and pentobarbital in LS mouse brain preparations, but did not alter GABA- activated 36Cl-uptake per se. In contrast to its antagonist effect versus other allosteric modulators, pressure did not antagonize these behavioral or in vitro effects induced by the neuroactive steroid, 3α-hydroxy-5β-pregnan- 20-one (3α,5β-P). These findings add to evidence that pressure directly and selectively antagonizes drug effects mediated through allosteric coupling pathways. The results fit predictions, and thus support the hypothesis that allosteric coupling pathways in GABA(A) receptors represent initial sites of action for ethanol. Collectively, the results suggest that there may be common physicochemical and underlying structural characteristics that define ethanol sensitive regions of receptor proteins and/or their associated membranes that can be identified by pressure within (e.g., GABA(A)) and possibly across (e.g., GABA(A), NMDA, 5HT3) receptors.

AB - The present study uses increased atmospheric pressure as an ethanol antagonist to test the hypothesis that allosteric coupling pathways in the GABA(A) receptor complex represent initial sites of action for ethanol. This was accomplished using behavioral and in vitro measures to determine the effects of pressure on ethanol and other GABAergic drags in C57BL/6 and LS mice. Behaviorally, exposure to 12 times normal atmospheric pressure (ATA) of a helium-oxygen gas mixture (heliox) antagonized loss of righting reflex (LORR) induced by the allosteric modulators ethanol and pentobarbital, but did not antagonize LORR induced by the direct GABA agonist 4,5,6,7- tetrahydroisoxazolo-pyridin-3-ol (THIP). Similarly, exposure to 12 ATA heliox antagonized the anticonvulsant effects verses isoniazid of ethanol, diazepam and pentobarbital. Biochemically, exposure to 12 ATA heliox antagonized potentiation of GABA-activated 36Cl-uptake by ethanol, flunitrazepam and pentobarbital in LS mouse brain preparations, but did not alter GABA- activated 36Cl-uptake per se. In contrast to its antagonist effect versus other allosteric modulators, pressure did not antagonize these behavioral or in vitro effects induced by the neuroactive steroid, 3α-hydroxy-5β-pregnan- 20-one (3α,5β-P). These findings add to evidence that pressure directly and selectively antagonizes drug effects mediated through allosteric coupling pathways. The results fit predictions, and thus support the hypothesis that allosteric coupling pathways in GABA(A) receptors represent initial sites of action for ethanol. Collectively, the results suggest that there may be common physicochemical and underlying structural characteristics that define ethanol sensitive regions of receptor proteins and/or their associated membranes that can be identified by pressure within (e.g., GABA(A)) and possibly across (e.g., GABA(A), NMDA, 5HT3) receptors.

KW - 3α-Hydroxy-5β-pregnan-20-one (3α, 5β-P)

KW - 4,5,6,7-Tetrahydroisoxazolo-pyridin-3-ol (THIP)

KW - Allosteric coupling hypothesis

KW - Anticonvulsant effect

KW - Barbiturates

KW - Benzodiazepines

KW - C57BL/6 mice

KW - Central nervous system

KW - Ethanol antagonist

KW - GABA(A) receptor complex

KW - GABA-activated chloride ion uptake

KW - Helium-oxygen gas mixture

KW - Hyperbaric exposure

KW - Ligand-gated ion channels

KW - Loss of righting reflex (LORR)

KW - N-Methyl-D-aspartate (NMDA)

KW - Neuroactive steroid

KW - γ-Aminobutryic acid (GABA)

UR - https://www.scopus.com/pages/publications/0032947573

UR - https://www.scopus.com/pages/publications/0032947573#tab=citedBy

U2 - 10.1007/s002130050843

DO - 10.1007/s002130050843

M3 - Article

C2 - 10090641

AN - SCOPUS:0032947573

SN - 0033-3158

VL - 141

SP - 339

EP - 350

JO - Psychopharmacology

JF - Psychopharmacology

IS - 4

ER -

In vivo and in vitro hyperbaric studies in mice suggest novel sites of action for ethanol

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