The effects of conditioning with amphetamine on the thermic effects of amphetamine and pentobarbital.

1. Rats were injected with amphetamine (1.5 mg/kg) in the presence of a distinctive set of environmental stimuli (CS1) and saline in the presence of a different set of environmental stimuli (CS2) on different days for a total of 10 amphetamine and 20 saline injections. 2. The hyperthermic effect of amphetamine first increased but then declined to levels seen during the very first drug administration. 3. Following the conditioning phase, half the rats were injected with amphetamine in CS1 and half in CS2. Although there was little thermic effect of amphetamine injected in CS1, there was pronounced hyperthermia following amphetamine in CS2. 4. Next, pentobarbital (30 mg/kg) was administered to half the rats in CS1 and half in CS2. The hypothermic effect of pentobarbital was attenuated in CS2.