DOPAMINERGIC AND CHOLINERGIC CONTROL OF ARGININE-VASOPRESSIN SECRETION IN TYPE-I DIABETIC MEN

Enhanced cholinergic and dopaminergic controls of anterior pituitary f unction have been described in insulin-dependent diabetes mellitus (ID DM). In order to verify whether similar neurotransmitter alterations a lso affect the regulation of posterior pituitary hormone secretion, th e arginine-vasopressin (AVP) responses to the dopaminergic agonist apo morphine and in a different occasion to physostigmine, an acetylcholin esterase inhibitor, were evaluated in normal (n=10) and type I diabeti cs (n=16). In addition, a control test with normal saline was performe d in all subjects. None of the diabetic patients were affected by neur opathy or other diabetic complications. They were divided into two gro ups according to the duration of their disease (less than 10 years: gr oup 1, n = 8; more than 10 years: group 2, n=8). Physostigmine (12.5 m u g kg(-1)) was infused intravenously over 10 min; apomorphine (60 mu g kg(-1)) was injected subcutaneously. Basal AVP concentrations were s imilar in all groups and remained constant during the control test. In contrast, both drugs induced significant increments in plasma AVP lev els in the normal controls and diabetic subjects. However, physostigmi ne- and apomorphine-induced AVP increments were twofold higher in diab etics than in control subjects. No significant differences were observ ed between diabetics of groups 1 and 2. No significant correlations be tween duration of diabetes and peak AVP responses to physostigmine or apomorphine were found within each group or when all diabetic subjects were considered together. These data indicate enhancement of both dop aminergic and cholinergic stimulatory regulations of AVP secretion in patients with uncomplicated IDDM, regardless of the duration of diabet es.