A POSSIBLE CENTRAL ANTINOCICEPTIVE EFFECT OF DIPYRONE IN MICE

The antinociceptive effect of dipyrone, a nonsteroidal antiinflammator y drug, was studied in a series of experiments employing tail-flick an d hot-plate models and the abdominal constrictor test. The drug was gi ven via intracerebroventricular (ICV), intrathecal (IT) or subcutaneou s (SC) routes, Dipyrone exhibited no analgesic activity in the tail-fl ick and hotplate tests while it inhibited the number of stretches in a dose-dependent manner. The antinociceptive effect of dipyrone adminis tered by the ICV and IT routes was almost completely reversed by nalox one treatment. The same procedure attenuated but not-completely inhibi ted the dipyrone action induced by SC administration. Histopathologica l examination revealed that IT dipyrone application produces no signif icant lesion in the spinal cord. The results suggest that dipyrone may exert a central antinociceptive action reversed by naloxone.