Printed in Great Britain LACK OF ANTIDIURETIC RESPONSE TO OSMOTIC STIMULI IN THE EARLY STAGES OF A WATER DIURESIS IN SHEEP

Abstract

When sheep or goats are given intrarumenal water loads of 100 ml/kg body wt they respond with a water diuresis beginning within 1 h and persisting for 3–4 h. Slow infusion of hypertonic NaCl solution into the third cerebral ventricle of goats causes prompt, transient and repeatable inhibition of such a water diuresis, due to the release of antidiuretic hormone (ADH) from the neurohypophysis (Andersson, Dallman & Olsson, 1969). However, intraventricular infusions of hypertonic sucrose are ineffective (Olsson, 1969). Because the latter observation appeared to be inconsistent with the osmoreceptor theory of the control of ADH release, it was desirable to test, in the ruminant animal, the classical observations made on the dog by Verney (1947). These observations demonstrated the antidiuretic effect of osmotic stimuli administered via the cerebral blood supply. Two Clun Forest ewes were used. One (body wt 35 kg) had a left carotid artery loop, and the