Abstract
The effect of age on the stimulatory control exerted by cholinergic- and angiotensin II (ANG II)-mediated neurotransmission on arginine vasopressin (AVP) secretion was evaluated by measuring and comparing the AVP responses to the administration of either the cholinesterase inhibitor physostigmine (13.5 µg/kg in 50 mL normal saline infused in 10 minutes) or ANG II (increasing doses of 4, 8, and 16 µg/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) healthy male subjects. Both drugs induced significant increments in plasma AVP levels in the youngest group, with mean peak levels 4.8 times higher than baseline at 20 minutes after the beginning of physostigmine infusion and 1.5 times higher than baseline at 60 minutes after the beginning of ANG II infusion. Similar responses were observed in the middle age group. Basal AVP levels in older subjects were similar to those observed in the other groups. However, the AVP increases induced by physostigmine (mean peak was 9 times higher than baseline) and ANG II (mean peak was 2.2 times higher than baseline) were significantly higher in the oldest group than in the other groups. These data suggest age-related enhancement of the stimulatory regulation exerted by cholinergic- and ANG II-mediated neurotransmission on AVP secretion.
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