Social influence on the response to drugs. III

Summary

Ninety-six 25 day old male albino rats were randomly assigned to three groups. One of these groups was observed at 30 days of age, a second at 45 days of age, and the third at 75 days of age. Animals in each of the groups were assigned to one of four subgroups, with eight animals in each subgroup. Animals in one subgroup received saline and were observed alone in an observation box, animals in a second subgroup received saline but were observed with three stimulus rats present in the observation box but separated from the observed animal by a wire-mesh barrier, rats in the third subgroup received 2.0 mg/kg of amphetamine and were observed in the solitary condition while rats in the fourth subgroup received the drug and were observed with the stimulus rats present.

Five categories of behavior were observed and recorded. These were: locomotion, barrier-directed behavior, sniffing, grooming, and inactivity. The number of times a rat shifted from one behavior category to another was also obtained.

Results showed that:

• 1. Barrier-directed behavior was significantly higher for 75 day old rats treated with amphetamine than for 30 or 45 day old animals.

• 2. Barrier-directed behavior was significantly higher for 75 and 45 day old amphetamine treated rats than for saline treated animals in comparable age groups.

• 3. There were no apparent differences in the amount of general activity engaged in by amphetamine treated rats in different age groups.