Selective potentiations in opioid analgesia following scopolamine pretreatment.

The effects of the muscarinic receptor antagonist scopolamine upon analgesia induced by D-ala-D-leu-enkephalin (DADL), beta-endorphin (BEND) and morphine were examined. While scopolamine (10 mg/kg, IP) significantly potentiated the analgesic responses following DADL (40 micrograms, ICV) and morphine (5 mg/kg, SC) on the jump test, it failed to alter significantly BEND (1 microgram, ICV) analgesia.