The influence of environmental variables on amphetamine-induced activity in the preweanling rat

Abstract

The present experiments investigated how environmental stimuli influence a behavioral response to amphetamine treatment in preweanling rats. In the first experiment, 15-day-old rats received either 1 mg/kg d-ampethamine or saline and were observed in the presence of their home shavings or in a novel cage. Results showed that although familiar cues from the home bedding decreased activity of the saline treated pups, these cues did not influence the activity-enhancing effect of amphetamine. In Experiment 2, 15-day-old pups were placed in a cage with an anesthetized adult conspecific and non-directed activity, around the cage, as well as directed activity on top of the adult were recorded. Following amphetamine treatment, animals tested with a conspecific showed no increase in non-directed activity, a finding which replicates previous observations. In the present experiment, however, a significant increase was seen in the activity directed towards or on top of the anesthetized adult. These experiments reveal that familiar cues per se are not sufficient to influence amphetamine-induced activity in young rats. Activity is influenced, specifically if familiar cues are associated with a discrete object. In the presence of a familiar stimulus, non-directed activity is decreased and directed activity is enhanced. These data are discussed in terms of clinical findings which slow that amphetamine acts to focus, or direct activity of the hyperactive child, and further underlines the importance of environmental variables in influencing the amphetamine response.