[Decreased beta-adrenergic receptor binding in the rat's brain on the activity-stress paradigm]

It was recently suggested that beta-adrenergic receptor binding in the rat brain was decreased by repeated electric shocks. In order to examine whether this phenomenon is observed under another stressor, the activity-stress paradigm was used in the present study. Rats were divided into 3 groups of AS, DC and AC.AS was housed in a cage with a running wheel and fed 1 hour daily. DC was fed in the same condition as AS, but housed in a cage without the wheel. AC was housed in a running wheel cage and fed in standard condition. AS exhibited excessive running and subsequently revealed sharp reduction of activity, body weight and food consumption on 7 or 8th experimental day. When these decrement was seen in AS, each rat was decapitated and beta-receptor binding was measured. AS showed excessive stomach ulcers, but DC and AC didn't. beta-Receptor binding in the cerebral cortex of AS was significantly lower than that of other groups. These results indicate that beta-receptor binding in the rat cortex was also decreased by the activity-stress paradigm.