Ability of some K + channel blockers to reverse inhibition of electrically evoked contractions of longitudinal muscle-myenteric plexus

Abstract

Blockers selective for different potassium (K +) channels were examined for their ability to reverse inhibition of electrically evoked contractions of longitudinal muscle-myenteric plexus (lm-mp) by adenosine analogs. Cyclohexyl adenosine (CHA) was selected for these studies, since it effectively inhibited contraction (EC 50 33 nM). 4-aminopyridine (4-AP) antagonized the inhibition by the adenosine analog, but also stimulated contraction by itself. α- and γ-dendrotoxin produced the most profound reversal of CHA-induced inhibition, while producing a minimal contraction alone. Other blockers produced only nominal reversal of the CHA-induced inhibition. These results suggest that inhibition by CHA is mediated via activation of and α- and γ-dendrotoxin-sensitive K + channel.