Antinociceptive effect of hydroxydihydrocarvone.

Hydroxydihydrocarvone (HC) is a synthetic intermediate obtained from R-(-)-carvone hydration. Due to the chemical and structural similarity between HC and other monoterpenes with psychopharmacological activity, this study was carried out to investigate the possible central antinociceptive effect of intraperitoneally administered HC, and to evaluate its effect on the opioid system in mice. In the tail immersion test, the time of the response to the thermal noxious stimulus was longer in the animals that received HC (200 mg/kg). In the hot plate test, HC (100-200 mg/kg) significantly increased the time mice stayed on the apparatus. In the formalin test, HC was effective in both phases of the test with significant dose-dependent response (50-200 mg/kg), showing central antinociceptive activity. In addition, HC (25-200 mg/kg) did not induce catalepsy in mice. In an attempt to evaluate the mechanism of action of HC, the mice were pretreated with naloxone (5 mg/kg, s.c.). The effect of HC on the formalin and hot plate tests was not blocked by naloxone. Therefore, HC has an antinociceptive effect on the central nervous system without causing catalepsy. These results suggest the nonparticipation of the opioid system in the modulation of pain by HC.