3-Methyl-5-hydroxy-5-trichloromethyl-1H-1-pyrazolcarboxyamide induces antinociception

The antinociceptive action of a novel pyrazole-derived compound, 3-methyl-5 -hydroxy-5-trichloromethyl-1H-1-pyrazolcarboxyamide (MPCA) was evaluated us ing the formalin and tail-immersion tests in mice. Anti-inflammatory activi ty was assessed by paw plethysmometry in adult rats using the carrageenin-i nduced paw edema test. Subcutaneous administration of MPCA (22, 66, and 200 mg/kg) induced a dose-dependent decrease in the time spent licking during the neurogenic and inflammatory phases of the formalin test, and preadminis tration of naloxone (1 mg/kg, sc) did not prevent MPCA-induced (200 mg/kg, sc) antinociception. Naloxone decreased the spontaneous locomotor activity of mice, while MPCA had no effect on locomotion. In contrast, administratio n of the opioid antagonist caused a significant increase in the locomotor b ehavior of mice previously injected with MPCA. MPCA was devoid of antinocic eptive action by the tail-immersion test and of anti-inflammatory activity. Moreover, MPCA had no effect on the motor performance of mice in the rotar od test. These results suggest that MPCA induces antinociception in the neu rogenic and inflammatory phases of the formalin test, an effect that does n ot involve opioid receptors. (C) 2001 Elsevier Science inc. All rights rese rved.