Acute effect of intracerebroventricular administration of zinc on the drinking behavior of rats induced by dehydration or central cholinergic and angiotensinergic stimulation.

1. Zinc is a metal important for several biological functions including neuromodulation and neurotransmission in the central nervous system. 2. In the present paper we studied the acute effects of third ventricle injections (2 microliters) of minute amounts of zinc acetate on the water intake of male, adult, Wistar rats (N = 7-14) under three conditions: water deprivation (14 h, overnight) and after third ventricle injections of carbachol (11 nmoles/rat in 2 microliters) or angiotensin II (AII, 9.6 pmoles/rat in 2 microliters). 3. Central injections of zinc acetate in different doses (0.3 and 3.0 nmoles/rat) induced a partial blockade of water intake of rats under all three conditions studied. Water intake after 120 min in control dehydrated rats (those receiving NaAc instead of Zn(Ac)2) was 7.89 +/- 0.47 ml while dehydrated animals receiving Zn(Ac)2 in the highest dose employed (3.0 nmoles/rat) was 2.90 +/- 0.75 ml. Carbachol-induced water intake after 45 min was 5.49 +/- 0.83 ml. This value was significantly reduced in zinc-treated (3.0 nmoles/rat) animals receiving carbachol (2.41 +/- 0.84 ml). Angiotensin-treated animals exhibit a water intake of 3.85 +/- 0.48 ml after 45 min, a value reduced to 1.13 +/- 0.6 ml in those animals receiving angiotensin II plus zinc (3.0 nmoles/rat). 4. It is suggested that zinc alters the functional integrity of cholinergic and angiotensinergic systems in the central nervous system mediating water-intake behavior in rats.