Rat dopamine hypersensitivity. I. Effect of age.

Two groups of 5 Sprague-Dawley rats were tested with either d-amphetamine or saline following our drug abuse-kindling model for dopaminergic hypersensitivity on pretest and posttest. However, when the animals were 40 weeks older, the saline group also received d-amphetamine. Thus, this group served as saline control for the initial two tests and-amphetamine control for age on the third session. The control group showed significantly more stereotyped behavior on Phase 3 as compared with the experimental group in the first session. These results suggest an increased responsivity of dopaminergic receptors with age as measured by stereotyped behavior in rats.