Liberation of antidiuretic hormone following hypothalamic stimulation in the dog

In 94 of 111 dogs, stimulation of the hypothalamus resulted in moderate to marked antidiuretic effects. The onset was slow (1/2–3 min) and the effect lasted for 15–35 min. These antidiuretic responses could be elicited by stimulating not only the points corresponding to supraoptic and paraventricular nuclei, but also a larger area in the hypothalamus. The antidiuretic action evoked by 20-sec excitation with stimuli of 7 v and 50 cycles/sec was roughly equivalent to that following intravenous administration of 2.5 mU/kg of Pitressin. Atropine and d-hyoscyamine did not block the antidiuretic responses to hypothalamic stimulation, but adequate amounts of n-ethyl-nortropinbenzhydrylether-hydrobromide and Dibenzyline did. The possible mechanism of such a phenomenon is discussed.