Dissociation of supraspinal and spinal morphine analgesia by reserpine

Reserpine antagonized systemic morphine analgesia as measured by tail-flick latency but the antagonism was surmountable by increasing the morphine dose. Reserpine had no effect on the intrathecal morphine analgesia while the analgesic action of intraventricular morphine was practically eliminated by reserpine.