Conditional hyperthermia in response to atropine associated with a hypothermic drug.

In a set of experiments designed to examine learned associations between drug states, atropine sulfate (10 mg/kg) elicited a conditional hyperthermia in rats following ten treatment sessions in which the drug was paired with either chlorpromazine hydrochloride (10 mg/kg) or ethanol (2.3 g/kg), both hypothermia-inducing agents. Atropine methyl nitrate, a quaternary analogue with similar peripheral effects but little central action, was ineffective as a cue in this situation. These experiments demonstrated that a sequential pairing of drug states can yield a change in an organism's response to the cue drug (the first drug in the sequence).