Effects of the benzodiazepine inverse agonist RO19-4603 alone and in combination with the benzodiazepine receptor antagonists flumazenil, ZK 93426 and CGS 8216, on ethanol intake in alcohol-preferring (P) rats

Abstract

The present study investigated dose dependence and time course effects of the benzodiazepine (BDZ) partial inverse agonist, RO19-4603 (0.005–0.30 mg/kg) alone, and in combination with the BDZ receptor antagonists flumazenil, ZK 93426, and CGS 8216 (20 mg/kg) in selectively bred alcohol-preferring (P) rats provided a two-bottle choice test between ethanol (EtOH) (10% v/v), and a palatable saccharin (0.0125% g/v) solution. A single dose of R019-4603 as low as 0.009 mg/kg selectively reduced EtOH drinking during the initial 15 min of a 4 h access to 19−0% of control levels on day 1. The 0.08, 0.15 and 0.30 mg/kg doses of R019-4603 significantly reduced total EtOH intake in the 4 h access period to 57−45% of controls on day 1. On day 2, no R019-4603 injections were given; however, six of the seven doses of R019-4603 (0.009, 0.02, 0.04, 0.08, 0.15, and 0.30 mg/kg) continued to reduce EtOH intake to 42−3% of control levels at the initial 15 min interval, while the 0.005, 0.009, 0.08, and 0.30 mg/kg doses reduced total 4 h EtOH intake to 60-42% of controls. Saccharin intake was either not altered by R019-4603 or showed increases during the initial 15 min intervals and the total 4 h sessions on days 1 and 2. Food intake was also unaffected by R019-4603. The CGS 8216, but neither flumazenil nor ZK 93426, reliably reversed the RO19-4603-induced suppression of EtOH intake on days 1 and 2. That certain BDZ inverse agonists can attenuate motivated behavior for EtOH reinforcement over a prolonged time course may provide a possible therapeutic approach to reducing EtOH consumption associated with alcoholism.