OXYTOCIN RESPONSE TO CHALLENGING STIMULI IN ELDERLY MEN

The present study was carried out in order to establish possible alter ations in oxytocin (OT) secretion with aging. Therefore, we evaluated the OT responses to insulin (0.15 U/kg)-induced hypoglycemia or to the administration of angiotensin II (i.v. infusion for 60 min of success ively increasing doses of 4, 8 and 16 ng/kg min; each dose for 20 min) or apomorphine (60 mu g/kg s.c.) in male subjects aged 22-80 yr and d ivided into 3 groups by age (group I (n = 9): 22-38 yr; group II (n = 9): 41-60 yr; group III (n = 9): 63-80 yr). Basal OT concentrations we re similar in all groups. The OT response during the insulin tolerance test and the administration of ANG II had similar patterns and magnit udes in all groups. The OT response to apomorphine was similar in the two younger groups, with plasma OT levels increased 118% vs. baseline. In contrast, apomoro, phine was unable to induce a significant OT ris e in the oldest group. During apomorphine test plasma OT concentration s were significantly lower in group III than in groups I and II. For t he first time in elderly human subjects, these data show normal respon siveness of the OT secretory system to releasing stimuli such as hypog lycemia and ANG II. These findings indicate that in aged men productio n of OT and capability of responding to challenging stimuli is unchang ed. On the other hand, the reduced OT responsiveness to apomorphine in group III might be an expression of the general dopaminergic dysfunct ion affecting the aging brain.