Antidiuretic responses to thermal stimulation of hypothalamus and spinal cord in the conscious goat

Abstract

At various ambient temperatures the effects of hypothalamus temperature and spinal cord temperature on urine formation and heat production were studied in conscious goats with chronically implanted thermodes. At neutral air temperature cooling hypothalamus or spinal cord induced a fall in urine volume and a rise in urine osmolality. This antidiuretic response was concurrent with a rise in heat production. Simultaneous occurrence of antidiuresis and increased heat production was also found after cessation of hypothalamic warming. At hot ambient temperature cooling hypothalamus affected neither urine formation nor heat production. Since hypothalamic cooling and spinal cord cooling produce identical effects on kidney function it is concluded that this response is linked to the complex cold defence activity as a whole. The predominent change of free water clearance is tentatively interpreted as caused by an increased ADH concentration in the blood during the cold defence activity.