Learning and cross drug effects: thermic effects of pentobarbital and amphetamine

The effects of environmental cues explicitly paired or unpaired with pentobarbital on the thermic effects of pentobarbital and amphetamine were investigated. Rats received 19 injections of pentobarbital in a distinctive environment and were subsequently tested for the thermic effects of pentobarbital and amphetamine in the distinctive environment, another environment previously associated only with saline, or in the colony room not previously associated with injections. Rats tested in the context of the environmental cues previously associated with pentobarbital were tolerant to the hypothermic effect of pentobarbital, but rats tested in the environment previously associated only with saline or in the colony room were not tolerant. Pentobarbital-experienced rats administered amphetamine in the context of the usual pentobarbital cues exhibited an exaggerated hyperthermic reaction compared to previously drug-naive rats administered amphetamine. Pentobarbital-experienced rats injected with amphetamine in the homeroom exhibited a smaller hyperthermic response than previously drug-naive rats administered amphetamine in the home room. These results demonstrate that an animal's response to a drug can be affected by cues paired and unpaired with drug administration.