Effects of hypothalamic microinjection of PGE2 on body temperature and sympathetic nervous activities in the rabbit.

The febrile response and sympathetic nervous response to hypothalamic microinjections of prostaglandin E2 (PGE2) were investigated in anesthetized rabbits. Microinjection of PGE2 (500-1000 ng) caused an increase in rectal temperature of more than 0.3 degrees C in 13 of 50 loci in the preoptic and anterior hypothalamic area (PO/AH). At 8 of these 13 loci, PGE2 elicited response patterns in the sympathetic nervous system, such as an increase in cutaneous sympathetic nervous activity and decrease in renal sympathetic nervous activity. This pattern of sympathetic nervous responses was induced with a simultaneous increase in rectal temperature of more than 0.5 degrees C. The 8 loci were distributed in the preoptic area, especially in the vicinity of the supraoptic nucleus. Electrolytic lesions of this region were made bilaterally, and intracerebroventricular injection of PGE2 (8 micrograms/kg) was found to inhibit fever and sympathetic activity. The results demonstrate that the action of PGE2 is responsible for the response patterns of sympathetic twigs during fever. The preoptic area, especially in the vicinity of the supraoptic nucleus, is most sensitive to PGE2 for the patternized response of sympathetic neurons and fever.