Systemic administration of prostaglandin E1 produces hypothermic effects in unanesthetized rats

The effects of intraperitoneal administration of prostaglandin E1 (PGE1) on thermoregulatory responses were assessed in unanesthetized rats at ambient temperatures (Ta) of 8, 22 and 29 degrees C. The body temperatures, metabolic rate, respiratory evaporative heat loss and vasomotor activity in response to PGE1 were observed. Intraperitoneal administration of PGE1 produced dose-dependent hypothermia at Ta's of both 8 and 22 degrees C. The PGE1 hypothermia was due to both the decreased metabolic rate and the cutaneous vasodilation. However, at a Ta of 29 degrees C, intraperitoneal administration of PGE1 produced no changes in rectal temperature, since the thermoregulatory responses were not affected by PGE1 application at this Ta. The data indicate that peripheral administration of PGE1 decreases metabolic heat production and increases heat loss, which leads to hypothermia in rats, in contrast to hyperthermia seen after central administration.