INFLUENCE OF THE SYMPATHETIC NERVOUS-SYSTEM ON RENAL-FUNCTION DURING HYPOTHERMIA

Hypothermia increases preglomerular vasoconstriction leading to decrea ses in renal blood flow (RBF) and glomerular filtration rate (GFR). Si nce plasma catecholamine concentrations are increased during hypotherm ia, the present study was performed to determine the role of the renal sympathetic nervous system in the cold-induced renal vasoconstriction . In Inactin(R) anaesthetized rats, hypothermia at 28 degrees C decrea sed GFR by 50% but failed to alter efferent renal sympathetic nerve ac tivity (ERSNA). Since hypothermia causes shivering which could have in fluenced the ERSNA recording, Inactin(R) anaesthetized rats were treat ed with pethidine or rats were anaesthetized with pentobarbital sodium or Saffan(R) to eliminate cold-induced shivering. In these non-shiver ing rats, hypothermia produced a reversible decrease in ERSNA in assoc iation with a fall in GFR that was of a similar magnitude as in shiver ing rats. Further studies in Inactin(R) anaesthetized rats showed that the fall in GFR was unaltered by renal denervation, bilateral adrenal ectomy or intrarenal administration of the alpha(1)-adrenoceptor antag onist prazosin. We conclude that cold-induced renal vasoconstriction i s not due to an increase in ERSNA or adrenaline/noradrenaline-mediated activation of renal alpha(1)-adrenoceptors.