Central cholinergic and adrenergic mechanisms in the release of antidiuretic hormone

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Abstract
1 Studies on the urine outflow, blood ADH concentration and electrolyte excretion were carried out in α-chloralose anaesthetized hydrated dogs; the agonists and antagonists of specific cholinoceptors and adrenoceptors were injected by the intracerebroventricular technique, to delineate the role of the C.N.S. receptors in the control of ADH secretion. 2 Central injection of acetylcholine elicited a dose-dependent antidiuretic response which was associated with an increase in the blood ADH titre. Central atropinization partially blocked the antidiuretic response. The remaining antidiuretic response was reversed to a diuretic one by further pretreatment with phenoxybenzamine. The diuretic response thus obtained could be blocked by propranolol. 3 The α-adrenoceptor agonists, phenylephrine and noradrenaline, induced dose-dependent antidiuretic responses with a concomitant rise in blood ADH concentration. Their effect could be blocked by pretreatment centrally with phenoxybenzamine. Low doses of adrenaline induced a diuretic response and a decrease in blood ADH concentration, higher doses elicited a dose-dependent antidiuretic response and increase in the titre of ADH in blood. Central phenoxybenzamine pretreatment reversed the antidiuretic effect of high doses of adrenaline to a diuretic effect which could be blocked by propranolol. 4 Isoprenaline elicited a dose-dependent diuretic response and a decrease in blood ADH titre and propranolol competitively blocked the effect of isoprenaline. 5 It is concluded that central muscarinic cholinoceptors and the α-adrenoceptors are concerned in the release of ADH, whereas the β-adrenoceptors are concerned with inhibition of ADH release.