NOREPINEPHRINE INHIBITION OF WATER AND FOOD-INTAKE - COMPARISON WITH VASOPRESSIN EFFECTS

In a previous publication we showed that intraperitoneally (IP) inject ed norepinephrine (NE) induces hypodipsia (hD) in rats by an alpha(1)- adrenergic effect which might be due to splanchnic vasoconstriction. I n the present work we administered two vasoconstrictive hormones: NE 2 50 ug/kg and arginine vasopressin (VP) 550 mU/kg either by IP or intra muscular (IM) route to fasted rats in two different thirst-inducing co nditions: (a) water-deprivation; or (b) induced hyperosmolarity. IP NE inhibited significantly food and water intake under both conditions. IM NE did not affect food intake and elicited significantly less hD an d this only in (a). VP did not affect food intake but induced hD regar dless of the route of administration in (a) but not in (b). NE adminis trated to anesthetized rats after food acid water deprivation increase d arterial pressure by both routes while VP effect was weaker and more variable. In conclusion: blood pressure elevation may be implicated i n the hD effect but IP NE elicits a specific splanchnic action; splanc hnic-induced hypophagia is not necessarily related to water intake inh ibition.