Oral administration ofl-arginine, a nitric oxide precursor, decreases nociceptive sensitivity in rats

Abstract

Tail-flick test was used to evaluate the effect of orally administeredl-arginine on nociceptive sensitivity of albino rats, which produced a) analgesia at 30 min postadministration lasting about 1.5 h (100 mg/kg); b) short-term analgesia (50 mg/kg); and c) no analgesic effect (250 mg/kg).d-Arginine (100 mg/kg) did not affect the nociceptive sensitivity. A significant NO increase took place in cerebral cortex at 30 min postadministration ofl-arginine in the given doses. At 1 h postadministration ofl-arginine in doses of 50 and 250 mg/kg, cortical NO content was lower than that in control animals. Analgesic effect ofl-arginine is presumably related to additional synthesis of NO. This effect seems to be not directly produced by NO, but is realized via other transmitter systems.