[Effect of haloperidol, diazepam and sodium oxybutyrate on the antinociceptive activity of opioid agonists administered via the theca medullaris spinalis].

At intrathecal administration the antinociceptive effect of morphine and DADL significantly exceeds the antinociceptive effect of pentazocine (ED50 in tail flick test were 1.1, 1.64, 75.0 nmol per mouse and in "writhing" test 0.0064, 0.0047, 24.53 nmol per mouse, respectively). All the agonists tested exhibited significantly higher activity at chemical stimulation than at thermal one. During the analysis of pA2 of naloxone during the interaction with morphine, DADL and pentazocine under thermal and chemical stimulation a pronounced mu-receptor component in the effect of DADL and pentazocine was suggested. A preliminary subcutaneous injection of sodium oxybutyrate (150 mg/kg) fails to change the activity of opioids administered intrathecally. Diazepam (5 mg/kg, subcutaneously) enhances the antinociceptive activity of DADL only at chemical stimulation. Haloperidol (2 mg/kg) increases the antinociceptive effect of morphine and DADL at pain stimulation of both types but exerts no influence on the analgesic effect of pentazocine. Haloperidol produces the most pronounced enhancement of the spinal component of delta-agonist DADL antinociceptive action. The enhancing effect of haloperidol is realized at the supraspinal level.