Regional differentiation of sympathetic nerve activity during fever caused by intracerebroventricular injection of PGE2.

In urethane-anesthetized rabbits prostaglandin E2 (PGE2) injected into a lateral cerebral ventricle (icv) produced hyperthermia. During the phase of rising rectal temperature, renal sympathetic activity monitored by multi-unit recording was reduced while the drop of ear skin temperature indicated cutaneous sympathetic activation. These reciprocal changes in activity corresponded to those typical for cold stress as well as for the phase of rising body temperature in fever induced by endotoxic lipopolysaccharides (LPS). However, a slight early stimulation of the heart rate after icv PGE2, contrasted to the initial reductions seen with LPS fever and in the cold. After sino-aortic denervation renal sympathetic inhibition in response to icv PGE2 was reduced but not abolished. After cervical vagotomy the antagonism between cutaneous and visceral sympathetic activity and the increase in heart rate became more prominent. During the phase of subsiding hyperthermia after icv PGE2, renal sympathetic activity returned to its control level, but, unlike LPS fever, did not exceed it. The results of this study indicate that the reciprocal changes in cutaneous and renal sympathetic activity, but not of sympathetic outflow to the heart, are identical during the phase of rising temperature in PGE2 and LPS fever. During the phase of subsiding hyperthermia, renal sympathetic activities change to different extents in PGE2 and LPS fever.