EFFECT OF INTRAPERITONEAL NITROPRUSSIDE AND ADRENERGIC AGONISTS ON FOOD AND WATER-INTAKE

In previous works it was shown that catecholamine-induced hypodipsia i s mediated by alpha(1)-adrenergic receptors while food intake (FI) inh ibition supposes also beta-adrenergic participation. We used sodium ni troprusside (N) as a vasodilator, alone or mixed with various adrenerg ic agonists and measured FI and water intake (WI) in rats either depri ved food and water overnight or in postprandial conditions after only 1 hour of deprivation in day time. N injected alone had no effect afte r overnight deprivation but diminished significantly norepinephrine (N E)-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 bur not in female rats. Isoproterenol (I) stimulated only WI (by 155%), while phenylephrine (P) and E inhibited it by 55%. In the prese nce 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, respecti vely. Only P-induced inhibition of WI was canceled in presence of N. T he results show that N, probably due to nitric oxide production, may i nduce hyperphagia and hyperdipsia in 1 hour-deprived male rats and als o that catecholamine effects on FI and WI are differently modulated by N. (C) 1998 Elsevier Science Inc.