Evidence for a 5-HT1D receptor-mediated hypothermic effect of the alpha 1-adrenoceptor agonist, SDZ NVI-085, in guinea-pigs.

The alpha 1-adrenoceptor agonist, SDZ NVI-085 ((-)-(4aR,10aR)-3,4,4a,5,10,10a-hexahydro-6-methoxy-4- methyl-9-(methylthio)-2H-naphth[2,3-b]-1,4-oxazine.HCl; 1 mg/kg i.p.), decreased body temperature of guinea-pigs. Two 5-HT1D receptor antagonists, GR127935 (N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2'-methyl-4'-(5-methyl- 1,2,4-oxadiazol-3yl)[1,1-biphenyl]-4-carboxamide) and PAPP (p-aminophenylethyl-m-trifluoromethylphenyl piperazine; both compounds at 1 mg/kg i.p., -30 min) blocked this response, whilst the alpha 1-adrenoceptor blocker prazosin (1 mg/kg i.p.) and the 5-HT1A receptor antagonist, SDZ 216-525 (methyl 4-(-[4-(1,1m3-trioxo-2H-1,2-benzoisothiazol-2-yl)butyl ]-1-piperazinyl)1H- indole-2-carboxylate; 1 mg/kg i.p.) were inactive. Another alpha 1-adrenoceptor agonist, St 587 (2-(2-chloro-5-trifluoromethylphenylimino)-imidazoline; 1 mg/kg i.p.) did not alter body temperature. SDZ NVI-085-induced hypothermia in guinea-pigs is probably mediated by 5-HT1D receptors.