The effect of in vitro and in vivo ethanol administration on [³⁵S]t-Butylbicyclophosphorothionate binding in C57 mice

Previous studies have shown that ethanol may produce some of its effects by facilitation of GABAergic transmission. One of the potential sites of drug action at the GABA receptor complex is the picrotoxin site, which can be studied with [³⁵S]t-butylbicyclophosphorothionate (TBPS). Ethanol inhibited the binding of [³⁵S]TBPS to C57 mice brain regions in vitro. This inhibition appears to be noncompetitive since ethanol decreased the B_max and not the K_D value of [³⁵S]TBPS. C57 mice were chronically treated with ethanol in liquid diet to determine if the sensitivity of TBPS binding is altered following chronic treatment or during withdrawal. Chronic treatment with ethanol and during withdrawal did not alter the K_D or B_max values of [³⁵S]TBS binding in C57 mice brain regions. It is suggested that the sensitivity of picrotoxin site on the oligomeric GABA receptor complex is not altered during ethanol tolerance or withdrawal. The effects of ethanol on GABA system may be mediated by its interaction with the coupling mechanism(s) or a direct effect on the chloride channels.