Pinacidil potentiates morphine analgesia.

The opening of K+ channels in the membrane of target neurons is a key mechanism of the effect of opioids. Here we show that the K+ channel opener, pinacidil, i.c.v. injected at doses of 50, 100 or 150 micrograms/rat, significantly increases and prolongs the effect of morphine on the thermal pain threshold (hot-plate and tail-flick tests). These data may suggest a novel approach to the management of pain.