STIMULATION OF CENTRAL 5-HT1D RECEPTORS CAUSES HYPOTHERMIA IN THE GUINEA-PIG

The 5-HT1 receptor agonist GR46611 (3-30 mg/kg s.c.) caused a dose-rel ated decrease in rectal temperature in the adult guinea-pig. A lower d ose (20 mu g) administered directly into the lateral cerebral ventricl e also caused a hypothermic response, suggesting that this effect is c entrally mediated. GR46611-induced (10 mg/kg s.c.) hypothermia was not attenuated by WAY100135 (3-10 mg/kg s.c.), ritanserin (0.3-1 mg/kg s. c.), spiperone (0.1-0.3 mg/kg s.c.) and ondansetron (0.1-1 mg/kg s.c.) , suggesting that 5-HT1A, 5-HT2A, 5-HT2C and 5-HT3 receptors are unlik ely to be involved in this response. In contrast, the poorly selective 5-HT receptor antagonist, metergoline (1-10 mg/kg s.c.), and the pote nt 5-HT1D receptor antagonist, GR127935 (0.1-1 mg/kg p.o.), antagonize d the effects of GR46611. The present data suggest that antagonism of GR46611-induced hypothermia may be useful for assessing the potency an d duration of action of centrally-acting 5-HT1D receptor antagonists i n the guinea-pig.