Mutation of the inhibitory ethanol site in GABAA ?1 receptors promotes tolerance to ethanol-induced motor incoordination.

ABSTRACT: Genes encoding the ?1/2 subunits of GABAA receptors have been associated with alcohol (ethanol) dependence in humans, and ?1 was also shown to regulate some of the behavioral effects of ethanol in animal models. Ethanol inhibits GABA-mediated responses in wild-type (WT) ?1, but not ?1(T6'Y) mutant receptors expressed in Xenopus laevis oocytes, indicating the presence of an inhibitory site for ethanol in the second transmembrane helix. In this study, we found that ?1(T6'Y) receptors expressed in oocytes display overall normal responses to GABA, the endogenous GABA modulator (zinc), and partial agonists (?-alanine and taurine). We generated ?1 (T6'Y) knockin (KI) mice using CRISPR/Cas9 to test the behavioral importance of the inhibitory actions of ethanol on this receptor. Both ?1 KI and knockout (KO) mice showed faster recovery from acute ethanol-induced motor incoordination compared to WT mice. Both KI and KO mutant strains also showed increased tolerance to motor impairment produced by ethanol. The KI mice did not differ from WT mice in other behavioral actions, including ethanol intake and preference, conditioned taste aversion to ethanol, and duration of ethanol-induced loss of righting reflex. WT and KI mice did not differ in levels of ?1 or ?2 mRNA in cerebellum or in ethanol clearance. Our findings indicate that the inhibitory site for ethanol in GABAA ?1 receptors regulates acute functional tolerance to moderate ethanol intoxication. We note that low sensitivity to alcohol intoxication has been linked to risk for development of alcohol dependence in humans.

SUBMITTER: Blednov YA 

PROVIDER: S-EPMC5543808 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature