Evidence for the presence of osmoreceptors in medulla of the dog.

Hypertonic solutions of different substances were injected into the vertebral artery of dogs anesthetized with chloralose, preventing their access to the hypothalamic osmoreceptors by ligating the basilar artery and both the external carotid arteries. The hypertonic solution of sodium chloride produced graded inhibition of water diuresis and a concomitant rise in plasma antidiuretic hormone (ADH) level; hypertonic solution of glucose produced lesser effect. Hypertonic urea solution, on the other hand, did not alter the course of water diuresis. It was concluded that osmoreceptors are also present in the medulla which sense the changes in blood osmolarity and accordingly modify the ADH release.