The Relaxant Effect Of Prazosin, Yohimbine and Hydralazine In Isolated Canine Portal Vein

Phenylephrine, clonidine and potassium chloride (KCL) were used as contractive agents in this in vitro study conducted in the canine vena portal, and prazosin, yohimbine and hydralizine were tested to inhibit the contractions due to the specified drugs. Phenylephrine and clonidine administered in cumulative concentrations produced dose-dependent contractions and these responses were inhibited noncompetitively by prazosin (10-6M) and yohimbine (10-8M, 10-6M). KC1 (80 mM) caused a topical and phasic contraction, this response was reduced by hydralazine given at ktimllative concentration. The findings suggest that alpha1 and alpha2 - adrenergic receptor antagonists and direct acting vasodilator drugs can be used to eliminate vena porta vasoconstriction.