iuretic and thermoregulatory responses to preoptic cooling in the monkey1

HAYWARD, JAMES N., AND MARY ANN BAKER. Diuretic and thermoregulatory responses to preoptic cooling in the monkey. Am. J. Physiol. 214(4) : 843-850. 1968.-Abrupt bilateral cooling with a Peltier biothermode in the midpreoptic region of the ad lib. hydrated rhesus monkey produced a brisk water diuresis, elevation of plasma osmolality, warming of the arterial blood, cooling of the skin, shivering, restlessness, and elevation of arterial blood pressure. Peak urine-flow values from this central thermal stimulus developed 30-45 min after the abrupt onset of hypothalamic cooling with no significant change in solute excretion, GFR, or ERPF. These diuretic responses were blocked by infusions of vasopressin without modification of the thermoregulatory responses to brain cooling. Thermode location in the preoptic area proved to be critical for the production of maximal diuretic and thermal responses to central cooling. Although air cooling produced a mild water diuresis in certain monkeys, environmental thermal stimuli were generally ineffective in modifying urine flow in our sitting, chair-restrained animals. Our study suggests that abrupt bilateral midpreoptic cooling in the monkey can inhibit the release of vasopressin from the neurohypophysis.