Protection from pentobarbital lethality mediated by Pavlovian conditioning.

The lethal effects of pentobarbital overdose were dependent upon the context in which the drug was administered. Rats received repeated injections of pentobarbital (30 mg/kg), in a distinctive environment and saline in the home room. At test, rats received a large dose (95 mg/kg) of pentobarbital. Fewer deaths occurred in a contex previously associated with drug administration. The results are consistent with a Pavlovian model of drug tolerance.