GABA(A) receptors modulate ethanol-induced conditioned place preference and taste aversion in mice

GABA(A) receptor antagonists have been shown to reduce ethanol self-administration and ethanol-induced conditioned taste aversion (CTA) in rats, suggesting a role for the GABA(A) receptor in modulating ethanol's motivational effects.

The present experiments examined the effects of the GABA(A) receptor antagonists, bicuculline and picrotoxin, on the acquisition of ethanol-induced conditioned place preference (CPP) and CTA in male DBA/2J mice.

Mice in the CPP experiments received four pairings of ethanol (2 g/kg) with a distinctive floor stimulus for a 5-min conditioning session (CS+ sessions). During CS+ sessions, mice also received bicuculline (0, 1.0, 3.0, or 5.0 mg/kg) or picrotoxin (2.0 mg/kg) before an injection of ethanol. On intervening days (CS- sessions), the pretreatment injection was always vehicle followed by saline injections that were paired with a different floor type. For the preference test, all mice received saline injections and were placed on a half grid and half hole floor for a 60-min session. For the CTA experiments, mice were adapted to a 2-h per day water restriction regimen followed by five conditioning trials every 48 h. During conditioning trials, subjects received an injection of vehicle, bicuculline (0.5 and 2.0 mg/kg), or picrotoxin (0.75 and 2.5 mg/kg) before injection of 2 g/kg ethanol or saline following 1-h access to a saccharin solution.

Both picrotoxin and the lowest dose of bicuculline (1.0 mg/kg) significantly increased the magnitude of CPP relative to vehicle-treated controls. Picrotoxin alone did not produce place conditioning. Ethanol-stimulated locomotor activity was significantly reduced during conditioning trials with picrotoxin and the higher doses of bicuculline (3.0 and 5.0 mg/kg). Bicuculline did not alter ethanol-induced CTA; however, picrotoxin dose-dependently increased the magnitude of ethanol-induced CTA. Bicuculline and picrotoxin did not produce CTA when administered alone.

Overall, these results suggest that blockade of GABA(A) receptors with bicuculline and picrotoxin enhances ethanol's motivational effects in the CPP paradigm; however, only picrotoxin enhances ethanol's motivational effects in the CTA paradigm.