Effect of intraperitoneal nitroprusside and adrenergic agonists on food and water intake

In previous works it was shown that catecholamine-induced hypodipsia is mediated by alpha1-adrenergic receptors while food intake (FI) inhibition supposes also beta-adrenergic participation. We used sodium nitroprusside (N) as a vasodilator, alone or mixed with various adrenergic agonists and measured FI and water intake (WI) in rats either deprived food and water overnight or in postprandial conditions after only 1 hour of deprivation in day time. N injected alone had no effect after overnight deprivation but diminished significantly norepinephrine (NE)-induced inhibition of both intakes, while epinephrine (E) inhibited only FI. In day time, N stimulated 30 min FI by 60% and WI by 84% in male but not in female rats. Isoproterenol (I) stimulated only WI (by 155%), while phenylephrine (P) and E inhibited it by 55%. In the presence of N, I increased WI even more (by 220%) but reduced FI. P + N and E + N increased FI by 41% and 128% as compared with P and E, respectively. Only P-induced inhibition of WI was canceled in presence of N. The results show that N, probably due to nitric oxide production, may induce hyperphagia and hyperdipsia in 1 hour-deprived male rats and also that catecholamine effects on FI and WI are differently modulated by N.