Correlation between brain adenyl cyclase activity and spontaneous motor activity in rats after chronic reserpine treatment

Reserpine (0.5 mg/kg) was administered daily to rats for a period of 8–12 days. Motor activity was measured 23–24 h after each injection. Twenty-four hours subsequent to the last reserpine injection, animals were sacrificed for determination of whole brain catecholamine concentration and adenyl cyclase activity. Rats which had shown a depression of motor activity after 3 days of treatment were hyperactive after 8–12 days. Brain norepinephrine concentrations in reserpine-treated animals ranged from 5 to 11% of control levels. In brain preparations from reserpine-treated rats, basal adenyl cyclase activity was unchanged from control, but the stimulation of cyclase activity produced by 10−4M norepinephrine was more than twice as great as that seen in controls. There was a strong positive correlation between the change in motor activity and the response of adenyl cyclase to norepinephrine, suggesting that the change in adenyl cyclase responsiveness may account for some of the increase in spontaneous activity occurring in rats after chronic reserpine treatment.