ACTIVATION OF CENTRAL ATP-SENSITIVE POTASSIUM CHANNELS PRODUCES THE ANTINOCICEPTION AND SPINAL NORADRENALINE TURNOVER-ENHANCING EFFECT IN MICE

ICV cromakalim, a K+ channel opener, produced antinociception. This ef fect was completely antagonized by ICV glibenclamide, a selective aden osine triphosphate-sensitive K+ channel (K-ATP channel) blocker. Furth ermore, direct opening of central K-ATP channels by ICV cromakalim inc reased the spinal noradrenaline (NA) turnover. On the other hand, the antinociception induced by ICV morphine (mu opioid agonist), but not I CV U-50,488H (kappa opioid agonist) was markedly potentiated by cromak alim. These findings suggest that the opening of central K-ATP channel s may elicit the antinociceptive effect and activate the descending NA ergic pathway, and central K-ATP channels play an important role as a modulator of the antinociception induced by mu agonists but not kappa agonists.