Inhibition of pituitary adenylate cyclase activating polypeptide induced relaxation of XXXX tracheal smooth muscle by charybdotoxin.

@entity840 @entity9443 @entity1919 @entity11697 @entity141
The aim of the present study was to investigate whether or not charybdotoxin (CAS 95751-30-7, @entity9443 ), a selective and potent @entity141 -dependent K+ channel blocker, inhibits the relaxation of @entity840 tracheal smooth muscle induced by pituitary adenylate cyclase activating polypeptides with 27 residues ( @entity11697 ) and with 38 residues ( @entity11697 ). Two forms of PACAP were discovered in hypothalamic tissues, and are known to increase the tissues @entity1919 levels and to be independent of beta-adrenoceptors. The relaxant effects of these polypeptides were evaluated by measuring the isometric tension of tracheal smooth muscle of @entity840 in vitro. Both forms of PACAP showed dose-dependent relaxant effects. The pD2 of @entity11697 was 7.01 +/- 0.04 and that of @entity11697 was 6.43 +/- 0.05. ChTX (10(-12)-3 x 10(-9) mol/l) did not affect the resting tension of the @entity840 tracheal smooth muscle. ChTX (10(-8) mol/l) slightly increased the tension, in some experiments being considered as a phasic tension change. ChTX (10(-8) mol/l) caused a small but significant rightward shift in the concentration-response curves of @entity11697 and @entity11697 . ChTX decreased the pD2 of @entity11697 to 6.74 +/- 0.03 and that of @entity11697 to 6.25 +/- 0.04. These results suggest that @entity1919 -mediated activation of @entity141 -dependent K+ channels may play an important role in the relaxation of the @entity840 tracheal smooth muscle induced by both forms of PACAP as well as beta-agonist.
