LOWERING OF THE BODY TEMPERATURE INDUCED BY VASOPRESSIN

1. In normal rats intraperitoneal as well as intravenous in jections of Pitressin and synthetic lysine vasopressin caused a prompt fall in the rectal temperature. Pitocin and Syntocinon had no effect on it.2. Intracarotid infusion of 8.5 per cent sodium chloride and 2 M sucrose solutions resulted in a lowering of the rectal temperature in normal rats, but not in neurohypophysectomized ones. Intravenous infusion of the hypertonic solutions and intracarotid infusion of isotonic solutions did not cause any change in the rectal temperature.3. Exposing neurohypophysectomized and totally hypophysectomized rats to a high ambient temperature of 40°C for 40 minutes resulted in a similar rise of the rectal temperature in extent and mode to that in normal ones. In rats with anterior hypothalamic lesions the rectal temperature rose to a higher level over 41°C on exposure to the same heat conditions.4. Subcutaneous injection of Pitressin tannate in oil caused a prolonged fall in the rectal temperature, but it did not exhibit any suppressing effect on the elevation of rectal temperature either in normal or in neurohypophysectomized rats which were subjected to heat exposure.5. No difference was observed between intracarotid and intravenous route of Pitressin administration in the extent and the time course of the fall in the rectal temperature.6. The fall in the rectal temperature following intravenous infusion of Pitres-sin was not modified by electrolesions in the anterior hypothalamic area, neurohypophysectomy and total hypophysectomy.7. Neither treatment with Dibenzylin nor atropine affected the body temper-ature lowering effect of Pitressin.