ON A POSSIBLE DUAL ROLE FOR CENTRAL NORADRENALINE IN THE CONTROL OF HYDROMINERAL FLUID INTAKE

1. Noradrenaline (NOR) is a neurotransmitter present in the central ne rvous system which is related to the control of ingestive behavior of food and fluids. We describe here the relationship between NOR and int ake of water and NaCl solution, fluids that are essential for a normal body fluid-electrolytic balance. 2. Central NOR has an inhibitory eff ect on fluid intake, but it either induces or not alterations in food intake. Several ways of inducing water intake, such as water deprivati on, meal-associated water intake, administration of angiotensinergic, cholinergic or beta-adrenergic agonists, or administration of hyperosm otic solutions, are inhibited by alpha-adrenergic agonists. Need-induc ed sodium intake by sodium-depleted animals is also inhibited by alpha -adrenergic agonists. 3. NOR can also facilitate fluid intake. Water i ntake is elicited by NOR and the integrity of central noradrenergic sy stems is necessary for a normal expression of water ot salt intake in dehydrated animals. The angiotensinergic component of either behavior apparently depends on a central noradrenergic system. NOR probably fac ilitates fluid intake by acting on postsynaptic receptors, but we do n ot know how it inhibits fluid intake. 4. The inhibitory and facilitato ry effects of NOR on ingestive behavior suggest a dual role for this n eurotransmitter in the control of hydromineral fluid intake.