Little evidence of a role for the α1GABAA subunit-containing receptor in a rhesus monkey model of alcohol drinking.

BACKGROUND: Alcohol potentiates GABAergic neurotransmission via action at the GABAA receptor. α1 subunit-containing GABAA receptors have been implicated as mediators, in part, of the behavioral and abuse-related effects of alcohol in rodents. METHODS: We systematically investigated the effects of 1 α1-preferring benzodiazepine agonist, zolpidem, and 2 antagonists, ß-carboline-3-carboxylate-tert-butyl ester (ßCCT) and 3-propoxy-ß-carboline hydrochloride (3-PBC), on oral self-administration of alcohol (2% w/v) or sucrose solution and observable behavior in rhesus macaques. We compared these effects to those of the nonselective benzodiazepine agonist triazolam, antagonist flumazenil, and inverse agonist ß-carboline carboxylate (ßCCE). RESULTS: Alcohol and sucrose solutions maintained reliable baseline drinking behavior across the study. The α1-preferring compounds did not affect intake, number of sipper extensions, or blood alcohol levels (BALs) at any of the doses tested. Zolpidem, ßCCT, and 3-PBC increased latency to first sipper extension in animals self-administering alcohol, but not sucrose, solution. Triazolam exerted biphasic effects on alcohol-drinking behavior, increasing intake at low doses but decreasing BAL and increasing latency at higher doses. At doses higher than those effective in alcohol-drinking animals, triazolam increased sucrose intake and latency. Flumazenil nonsystematically increased number of extensions for alcohol but decreased BAL, with no effects on sucrose drinking. ßCCE decreased sipper extensions for alcohol and increased latency for first sucrose sipper extension, but full dose-effect relationships could not be determined due to seizures at higher doses. CONCLUSIONS: Alcohol-drinking animals appeared more sensitive to the effects of GABAergic compounds on drinking behavior. However, these results do not support a strong contribution of α1GABAA receptors to the reinforcing effects of alcohol in primates.

Cognition-impairing effects of benzodiazepine-type drugs: role of GABAA receptor subtypes in an executive function task in rhesus monkeys.

The present studies evaluated the role of α1 and α5 subunit-containing GABAA receptors (α1GABAA and α5GABAA receptors, respectively) in the ability of benzodiazepine (BZ)-type drugs to alter performance in the cognitive domain of executive function. Five adult female rhesus monkeys (ages of 9-17years old) were trained on the object retrieval with detours (ORD) task of executive function. For the ORD task, the monkeys were required to retrieve food items from a clear box with one open end that was rotated to different positions along with varying placements of food. When the non-selective BZ triazolam and the α1GABAA-preferring agonists zolpidem and zaleplon were evaluated in the ORD task, deficits in performance occurred at doses that did not increase the latency of monkeys to initiate responding and/or increase the percentage of reaches that were incorrect (i.e., reaches in which food was not obtained). Cognition-impairing effects of triazolam and zolpidem in ORD were blocked by the α1GABAA-preferring antagonist, ßCCT, whereas the α5GABAA-preferring antagonist XLi-093 blocked the effects of triazolam but not zolpidem. While these findings suggest a role for both α1GABAA and α5GABAA receptor mechanisms, α1GABAA receptor mechanisms appear to be sufficient for impairments in executive function induced by BZ-type drugs.