Knockin Mice with Ethanol-Insensitive α1-Containing γ-Aminobutyric Acid Type A Receptors Display Selective Alterations in Behavioral Responses to Ethanol

Abstract

Despite the pervasiveness of alcohol (ethanol) use, it is unclear how the multiple molecular targets for ethanol contribute to its many behavioral effects. The function of GABA type A receptors (GABA A -Rs) is altered by ethanol, but there are multiple subtypes of these receptors, and thus far, individual subunits have not been definitively linked with specific behavioral actions. The ␣1 subunit of the GABA A -R is the most abundant ␣ subunit in the brain, and the goal of this study was to determine the role of receptors containing this subunit in alcohol action. We designed an ␣1 subunit with serine 270 to histidine and leucine 277 to alanine mutations that was insensitive to potentiation by ethanol yet retained normal GABA sensitivity and constructed knockin mice containing this mutant subunit. Hippocampal slice recordings from these mice indicated that the mutant receptors were less sensitive to ethanol's potentiating effects. Behaviorally, we observed that mutant mice recovered more quickly from the motor-impairing effects of ethanol and etomidate, but not pentobarbital, and showed increased anxiolytic effects of ethanol. No differences were observed in ethanol-induced hypnosis, locomotor stimulation, cognitive impairment, or in ethanol preference and consumption. Overall, these studies demonstrate that the postsynaptic effects of ethanol at GABAergic synapses containing the ␣1 subunit are important for specific ethanol-induced behavioral effects.Alcohol (ethanol) has a prominent role in society and is one of the most frequently used and abused drugs. Despite the prevalence of alcohol use, the molecular mechanisms underlying its behavioral effects remain unclear. Ethanol intoxication elicits a diverse array of behavioral effects including cognitive impairment and motor incoordination, and these behavioral effects are likely due to actions of ethanol on multiple brain proteins (Harris, 1999). GABA type A receptors (GABA A -Rs) are ligand-gated ion channels that mediate

Ethanol Modulates the Interaction of the Endogenous Neurosteroid Allopregnanolone with the α1β2γ2L GABAA Receptor

“…Consistent with the latter finding, mice lacking the ␣6 subunit had ethanol-induced sleep times comparable with those in wild-type mice, whereas ␦ subunit knockout mice had mostly unaltered ethanol-induced behavioral effects (Homanics et al, 1997;Mihalek et al, 2001). In addition, the role of the ␣1 subunit in at least some effects of ethanol has been conclusively shown by experiments on knockout and knockin mice (Blednov et al, 2003;Kralic et al, 2003;Werner et al, 2006). Results from the present work further support the role of ␣1 subunit-containing receptors in ethanol-induced changes in the central nervous system.…”

Behavioral Characterization of Knockin Mice with Mutations M287L and Q266I in the Glycine Receptor α1 Subunit

“…A significant shortcoming of null mutant mice is that extensive compensation may occur in response to the deletion and may involve genes that are distinct from the deletion. One assumption underlying construction and use of KI mice is that they will display either no or limited compensation compared with knockout mice, thus providing an advantage over null mutants (Werner et al, 2006;Blednov et al, 2011;Harris et al, 2011). However, the mutations used in this study clearly impair the function of the GlyR, and we asked whether some of the changes in behavior that we observed were the result of compensation occurring during development or from the acute impairment in GlyR function.…”

Adolescent and adult rat cortical protein kinase A display divergent responses to acute ethanol exposure

“…The hypnotic effects of ethanol were assessed using the LORR paradigm as described elsewhere (Werner et al, 2006). Briefly, all animals were cannulated using the procedures outlined above.…”