Mechanism of the Tracheal Smooth Muscle Relaxant Activity of the Cordia myxa Plant Extract in Sheep Muhannad A. A. AlBayaty and Farid J.. AlTahan

Abstract

Isolated tracheal smooth muscle of sheep, which is pharmacologically
precontracted by acetylcholine, induces relaxation when exposed to Cordia
myxa plant extract. The aim of the present study was to typify the mechanism of
Cordia myxa extract induced by relaxation in the sheep trachea. 1. Cordia myxa
extract relaxed both epithelium-intact and denuded sheep trachea rings
contracted by acetylcholine. The scale of relaxation on Cordia myxa extract was
dependent on the treated dose and slightly greatly in epithelium denuded rings
than in epithelium-intact preparations. 2. L-NAME (10 nM-100 uM) but not DNAME
completely inhibited the relaxation in a concentration dependent
manner. 3. The Cordia myxa extract -induced relaxation was inhibited by
methylene blue (1 -100 uM), and verapamil (100 nM), and removal of
extracellular Ca2+. In contrast, Cordia myxa extract - induced relaxation was
potentiated by Nw-nitro-Larginine (L-NOARG) treatment. These results put
forward that Cordia myxa extract -induced relaxation may be due to nitric oxide
from exogenously administered L-arginine as well as endogenous nitric oxide
donors such as amino acid and arginine derivatives. Additional suggestion is that
Cordia myxa extract stimulates the expression of nitric oxide synthesis, and its
activity for nitric oxide generation is dependent on cytosolic Ca2+ originated
from extracellular space