Effect of ambient temperature on development of prostaglandin E1 hyperthermia in the rhesus monkey

Prostaglandin E1 (PGE1) hyperthermia (fever) was studied at ambient temperatures (Ta) of 18, 27, and 35 degrees C in four male unanesthetized rhesus monkeys (Macaca mulatta) implanted with four guide tubes and one reentrant tube within the preoptic anterior hypothalamus (PO/AH). Rectal, hypothalamic, and mean weighted skin temperatures, O2 consumption, CO2 production, and respiratory and total evaporative water losses were measured continuously before and during PGE1 fever at each Ta. The febrile reponse to PO/AH PGE1 injection was dose responsive and was less at a Ta of 35 degrees C than at the other Ta's. At a Ta of 18 degrees C, fever was brought about primarily by an increase in metabolic rate. At a Ta of 27 degrees C, fever was produced by an increase in metabolic rate and by skin vasoconstriction. At a Ta of 35 degrees C, fever was the result of an increase in metabolic rate and a decrease in sweating evaporative heat loss. At each Ta some generalized skin vasconstriction also occurred. During the plateau phase of the fever, the measured heat losses and gains returned to near control levels. The data indicate that the rhesus monkey shows specific thermoregulatory responses to PO/AH PGE1 injection and would be a good model for the study of thermoregulation during fever in higher primates.