Modulation of GABA binding to rat brain membranes by alkyl beta-carboline-3-carboxylate esters

The effects of the methyl, ethyl and propyl esters of beta-carboline-3-carboxylic acid were assessed on low affinity binding of GABA to rat brain membranes, and the enhancement of such binding by diazepam. The propyl ester acted as a benzodiazepine agonist in enhancing low affinity GABA binding, while the methyl and ethyl esters acted as benzodiazepine antagonists in reversing the stimulation of GABA binding by diazepam. These effects on low affinity GABA binding in vitro are consistent with pharmacological and behavioural actions of these esters in vivo and support the hypothesis that such actions are mediated via a GABA-benzodiazepine receptor complex.