The antinociceptive effects induced by L-arginine (L-Arg 300-600 mg sc) or N(G)-nitro-L-arginine (NOArg 20-70 mg sc) in mice were assessed by the hot-plate test. The antinociception induced by both agents was antagonized by naloxone. L-Arg significantly reduced the effects of the largest doses of morphine (3, 5, and 10 mg/kg) or pentazocine (7.5, 15, and 30 mg/kg). Morphine antagonized L-Arg-induced antinociception but did not change the responses to NOArg. Diltiazem (10 mg/kg) or verapamil (10 mg/kg) decreased L-Arg antinociceptive responses, whereas the effects of NOArg were enhanced. The antinociceptive effects of L-Arg and NOArg were also tested in mice rendered tolerant to morphine or pentazocine. Whereas the effect of L-Arg were lower in tolerant animals, the responses to NOArg were unchanged. The results suggest the involvement of opiate mechanisms and NO synthesis in L-ARG-induced antinociception and a lesser influence of opiate mechanisms in the antinociception induced by NOArg.
CITATION STYLE
Contreras, E., Germany, A., Gonzalez, P., & Norris, B. (1997). Influence of opiate tolerance and calcium channel antagonists on the antinociceptive effects of L-arginine and N(G)-nitro-L-arginine. General Pharmacology, 28(3), 443–448. https://doi.org/10.1016/S0306-3623(96)00295-9
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