Operant behavioural demonstration of qualitative differences between the d- and l-isomers of amphetamine☆

Publisher Summary This chapter elaborates the operant behavioral demonstration of qualitative differences between the d - and l -isomers of amphetamine. One of the major problems associated with studying the behavioral and/or neurochemical consequences of pharmacological agents is that no one unitary hypothesis can describe the mechanism by which drugs act. It is found that when a dose of 1 mg d -amphetamine sulfate/kg is administered to rats trained to bar-press for food pellets on a fixed ratio 30 schedule, the behavior is altered so that the subjects are responding at about 40% of control rates. A dose of 4 mg 1-amphetamine sulfate/kg likewise brought FR-30 responding down to about 40% of control. It is observed that when tolerance to the disruptive effect of either isomer developed, a challenge by the other isomer resulted in a demonstration of no cross-tolerance, suggesting differential mechanisms. It is found that if a more sensitive measure of operant behavior is used, one see a differential effect of d and l -amphetamine on components of fixed-interval responding.