Effects of calcitonin on the brain of aged rats.

We have recently demonstrated that calcitonin, a putative neuromodulator, may influence extrapyramidal motor system by decreasing nigro-striatal dopaminergic function. Since calcitonin is extensively used in aged patients, we have investigated whether calcitonin might influence extrapyramidal motor behavior (haloperidol-induced catalepsy and apomorphine-induced hyperactivity) in rats of different ages. Intracerebroventricular injection of salmon calcitonin (1 micrograms/kg) prevented apomorphine-induced hyperactivity in 2, 7, 18 or 21 month old rats, but potentiated haloperidol-induced catalepsy only in 2 or 7 month old rats. In addition, in all the animals salmon calcitonin significantly decreased the secretion of prolactin, an anterior pituitary hormone that may act at central level enhancing nigro-striatal dopaminergic activity.