Effects of intravenous and intraventricular prostaglandin E1 on thermoregulatory responses in rabbits.

The thermal responses produced by both systemic and central administration of prostaglandin E1 (PGE1) at the three different ambient temperatures (Ta) of 2, 22 and 32 degrees C were measured to assess the possible involvement of PGE1 in temperature regulation. The body temperatures, metabolic rate, respiratory evaporative heat loss and vasomotor activity in response to PGE1 were measured. Intravenous administration of PGE1 produced dose-dependent hypothermia at Ta's of both 2 and 22 degrees C. The PGE1 hypothermia was due to cutaneous vasodilation. However, at a Ta of 32 degrees C, intravenous PGE1 produced no changes in rectal temperature and ear blood flow. On the other hand, the direct injection of PGE1 into the third ventricle produced dose-dependent hyperthermia. At a Ta of 22 degrees C, PGE1 fever was due to decreased heat loss along with a small increase in heat production. In the cold, PGE1 fever was due to increased heat production while in the heat heat losses were decreased. The data suggest that elevating PGE1 levels in the periphery causes a hypothermia, while elevating PGE1 levels in the central nervous system causes a hyperthermia at Ta's of both 2 and 22 degrees C.