Effect of aging on the arginine-vasopressin response to physostigmine and angiotensin II in normal men

The effect of age on the stimulatory control exerted by cholinergic- and an giotensin II (ANG II)-mediated neurotransmission on arginine vasopressin (A VP) secretion was evaluated by measuring and comparing the AVP responses to the administration of either the cholinesterase inhibitor physostigmine (1 3.5 mu g/kg in 50 mt normal saline infused in 10 minutes! or ANG II (increa sing doses of 4, 8, and 16 mu g/kg/ min, each dose for 20 min) in 8 younger (23-37 years), 8 middle age (42-60 years), and 8 older (63-79 years) healt hy male subjects, Both drugs induced significant increments in plasma AVP levels in the young est group, with mean peak levels 4.8 times higher than baseline at 20 minut es after the beginning of physostigmine infusion and 1.5 times higher than baseline at 60 minutes after the beginning of ANG II infusion, Similar resp onses were observed in the middle age group, Basal AVP levels in older subj ects mere similar to those observed in the other groups, However, the AVP i ncreases induced by physostigmine (mean peak mas 9 times higher than baseli ne) and ANG II (mean peak was 2.2 times higher than baseline) were signific antly higher in the oldest group than in the other groups, These data sugge st age-related enhancement of the stimulatory regulation exerted by choline rgic- and ANG II-mediated neurotransmission on AVP secretion.