Dissimilarities between the Central Control of Thirst and the Release of Antidiuretic Hormone (ADH)

Effects of slow (7.5 μu1/min) infusions of certain hypertonic solutions into the 3rd brain ventricle were studied in 4 unanesthetized goats. The only solutions found to elicit drinking were NaCl (0.85 M) and to a minor degree) NaHCO3 (0.85 M). Other solutions tested (0.85 M solutions of Na-acetate and NH4Cl, and 1.7 M solutions of urea and d-glucose) were negative in this respect. During 1 hr infusions of NaCl a strong cumulative drinking response was obtained in all animals within 3 to 8 min after start of the infusion. No drinking occurred when the animals were hydrated prior to the infusion. The effects on water diuresis of short (2 to 10 min) periods of infusion of the same hypertonic solutions were studied in 3 goats after previous hydration. In 2 of the animals 4 min periods of infusion of the sodium salts and of NH4Cl caused an inhibition of water diuresis of the neurohypophysial type, paralleling the effect of an i.v. injection of approximately 4 mU of ADH. A considerably smaller effect was obtained by urea and no inhibition of water diuresis was seen due to infusions of d-glucose. In one of the goats no inhibition of water diuresis was obtained from either NaCl or NH4Cl. In this animal the site of infusion was more posterior and ventral in the 3rd ventricle than in the responding animals.