Autonomic thermoregulatory responses of febrile monkeys during microwave exposure

Adult male squirrel monkeys were stereotaxically implanted with Delrin injection cannulas and reentrant tubes in the medial preoptic nucleus of the hypothalamus (PO/AH). An injection into the PO/AH of 250 ng prostaglandin E₁ (PGE₁) in 1 μl sterile saline generated a controlled fever of 1.4±0.3°C. Autonomic mechanisms of heat production and heat loss were measured in febrile monkeys during 30 min exposures to 450 or 2450 MHz CW microwave (MW) fields at different phases of the fever cycle (induction, plateau, defervescence). Heat production was spared when MW exposure occurred early in the fever cycle; heat loss (vasodilation, sweating) was stimulated when MW exposure occurred during defervescence. The magnitude and pattern of autonomic response change was frequency dependent