A Study of Thirst and Other Effects of an Increased Sodium Concentration in the 3rd Brain Ventricle

The characteristics of thirst elicited by injections of hypertonic NaC1-solution into the 3rd brain ventricle were studied in goats supplied with permanent ventricular canola. Animals in normal water balance drank 1.5 to 2.0 1 of water within 2 min after the intraventricular injection of 0.1 ml of 0.85 M NaC1. In the hydrated animal this thirst response was markedly diminished or completely absent. If the goats were not allowed to quench their thirst immediately after the intraventricular injection of hypertonic NaC1, the urge to drink gradually became weaker and disappeared after about 20 min. Single or repetitive injections of 0.1 ml of 0.85 M NaCl into the 3rd brain ventricle were further found to cause a conspicuous increasz in urinary excretion of Na+ and C1– and to inhibit temporarily an established water diuresis. Aldosterone treatment did not prevent the increase in urinary electrolyte excretion occurrinz after injections of hypertonic NaCl into the 3rd ventricle. Repetitive injections of 0.1 ml of 0.85 M NH4Cl or of 1.7 M d-glucose into the 3rd ventricle, or injections of 0.1 ml of 0.85 M NaCl into the lateral ventricle did not induce drinking or cause any increase in urinary electrolyte excretion.