A comparison of diazepam stimuli in aged and adult rats.

Young adult rats (5 months) were compared with aged (28 months) rats in their ability to learn and perform in a diazepam drug discrimination. Both groups of rats were drug naive at the onset of the experiment. Adult and aged animals learned to discriminate diazepam. In general, the response rates under both drug and vehicle conditions were significantly lower for the aged group. The diazepam stimuli were dose-dependent in each group. Similar dose-dependent generalization with chlordiazepoxide, pentobarbital, and methocarbamol was also noted in both the aged and adult animals. These data suggest that aged animals, who have experienced anxiolytic compounds over a period of time (in this case, repeated administration of diazepam in the discrimination procedure), respond in a similar fashion to drug treatment as do young adult animals, verifying the reliability and validity of results obtained in aging rats who are repeatedly exposed to drug treatment.