Effects of gamma-hydroxybutyric acid on metabolic, respiratory and vasomotor activities and body temperature in rats.

The effects of gamma-hydroxybutyric acid (GHBA) on metabolic, respiratory and vasomotor activities and body temperature were assessed in unanesthetized rats at three different ambient temperatures (Ta) of 8, 22 and 30 degrees C. Intraperitoneal administration of GHBA produced dose-dependent hypothermia in rats at both 8 and 22 degrees C Ta. At Ta = 8 degrees C the hypothermia was brought about solely by a decrease in metabolic heat production, while at Ta = 22 degrees C the hypothermia was due to both a decrease in metabolic heat production and an increase in cutaneous circulation (as indicated by changes in tail and foot skin temperatures). However, at Ta = 30 degrees C GHBA administration produced no changes in rectal temperature or other thermoregulatory parameters. Respiratory evaporative heat loss was not affected by GHBA application. Furthermore, it was found that the GHBA-induced hypothermia was antagonized by haloperidol (a selective blocker of dopamine receptors), but not by p-chlorophenylalanine (an inhibitor of serotonin synthesis). The data suggest that GHBA elicits a central dopamine receptor activation mainly via release of endogenous dopamine and leads to a hypothermia.