INVOLVEMENT OF ENDOGENOUS OPIOIDS AND ATP-SENSITIVE POTASSIUM CHANNELS IN THE MEDIATION OF CARBACHOL-INDUCED ANTINOCICEPTION AT THE SPINAL LEVEL - A BEHAVIORAL-STUDY IN RATS

The effects of intrathecally administered (i.t.) atropine, glibenclami de, a blocker of ATP-sensitive potassium channels, or naloxone on the antinociception produced by i.t. carbachol or morphine were observed i n rats by tail-flick (TF) test. The results showed that: (1) i.t. carb achol produced a dose-dependent antinociception and it could be antago nized by i.t. atropine; (2) the antinociception produced by i.t. carba chol could be blocked dose-dependently by i.t. glibenclamide or i.t. n aloxone; (3) the antinociception produced by i.t. morphine could be bl ocked dose-dependently by i.t. glibenclamide, but not by i.t. atropine . The results suggest that the antinociception produced by activation of muscarinic receptors at the spinal level might be mediated by endog enous opioids and ATP-sensitive potassium channels in a cascade form. (C) 1997 Elsevier Science B.V.