Adrenergic stimulation of the lateral hypothalamic area on sodium and potassium excretion

Abstract The effects of adrenergic stimulation of the lateral hypothalamic area on sodium and potassium excretion were studied in rats bearing implanted cannulae. When noradrenaline was injected into several points of the lateral hypothalamic area, a dose-related increase in natriuresis and kaliuresis was observed. Rats previously injected through the same cannulae with α (Regitine) or β (Propranolol) blocking agents showed different natriuretic responses when injected with noradrenaline. It was observed that the normal noradrenaline-induced natriuresis was abolished by the α-adrenergic blockers, while β-adrenergic blockers increased the response. Intrahypothalamic injection of Isoproterenol, an activator of the β-adrenergic receptor, induced a decrease in natriuresis, kaliuresis and urinary volume. In contrast, injection of Metaraminol, an α-adrenergic agonist, caused an increase in sodium and potassium excretion and a reduction of urinary volume. Drugs blocking the destruction of noradrenaline or its reuptake by the presynaptic nerve endings potentiated 2-fold the action of 20 nmol of noradrenaline. These experiments provide good evidence for the existence of an adrenergic mechanism consisting of α and β receptors which works antagonistically on the regulation of sodium and potassium excretion. The excretion of the two electrolytes is stimulated by the α-adrenergic system, and inhibited by the β-adrenergic system.