ROLE OF SEIZURE ACTIVITY IN THE DECREASED PINEAL RESPONSE TO ISOPROTERENOL IN RATS CHRONICALLY TREATED WITH ELECTROCONVULSIVE SHOCK

Chronic electroconvulsive shock (ECS) has been previously reported to blunt the melatonin response to acute isoproterenol administration in rats. To assess whether electrically induced seizures are indeed requi red for the appearance of the blunted pineal response to isoproterenol , pineal and serum melatonin levels were measured after isoproterenol stimulation in rats treated with ECS (80 mA, 0.5 sec), subconvulsive s hock (15 mA, 0.5 sec), or sham-ECS once per day at 11:30-12:00 h for 8 days. In ECS-treated rats, both pineal and serum melatonin levels aft er isoproterenol administration were significantly lower than those in sham-treated animals and in rats receiving subconvulsive shock. Moreo ver, as compared with sham treatment, chronic subconvulsive shock did not affect the melatonin response to isoproterenol. These data show th at seizure activity is indeed required for the ECS-induced decrease in the pineal response to acute beta-adrenergic stimulation.