POSSIBLE INVOLVEMENT OF NITRIC-OXIDE IN ARGININE-INDUCED ANALGESIA

Intracerebroventricular injection (icv) of 1-arginine (Arg, 0.5, 5.0, 50 mug) produced a dose-dependent prolongation in the hot-plate latenc y in mice. A similar result was obtained when nitroprusside (0.1, 1.0, 10 mug, icv) was given. Naloxone (2 mg . kg-1, ip) failed to antagoni ze the effects of Arg or nitroprusside. But Arg-induced antinociceptio n was attenuated by N(G)-monomethyl-arginine (NMMA, 10 mug). 8-Bromogu anosine 3' : 5' cyclic monophosphate (bromo-cGMP, 50 mug) also produce d an antinoceptive effect. The results suggest that Arg induces an ana lgesia possibly via activation of nitric oxide-cGMP pathway.