Possible involvement of nitric oxide in arginine-induced analgesia.

Intracerebroventricular injection (icv) of 1-arginine (Arg, 0.5, 5.0, 50 micrograms) produced a dose-dependent prolongation in the hot-plate latency in mice. A similar result was obtained when nitroprusside (0.1, 1.0, 10 micrograms, icv) was given. Naloxone (2 mg.kg-1, ip) failed to antagonize the effects of Arg or nitroprusside. But Arg-induced antinociception was attenuated by NG-monomethyl-arginine (NMMA, 10 micrograms). 8-Bromoguanosine 3': 5' cyclic monophosphate (bromo-cGMP, 50 micrograms) also produced an antinociceptive effect. The results suggest that Arg induces an analgesia possibly via activation of nitric oxide-cGMP pathway.