Effect of haloperidol on the analgesic activity of opiate agonists administered intracisternally and intrathecally

: The mu-agonist morphine more actively inhibited the complex reflex manifestations of pain responses (the Hafner test and hot plate) in mice as compared to the spinal pain reflexes (tail flick). The delta-agonist D-Ala2-D-Leu5-enkephalin (DADL) abolished the responses of both types in the same doses. Haloperidol potentiated the ability of morphine and DADL to inhibit nociceptive responses at the cerebral level. The potentiating effect of this neuroleptic on inhibition of spinal nociceptive responses by opiate agonists was only observed at a dose of 5 mg/kg. Haloperidol could also in some of the tests potentiate the antinociceptive effect of the kappa-agonist bremazocine and the sigma-agonist SKF 10.047, however their activity was significantly lower than that of morphine and DADL.