Antagonistic effects of changrolin on the contraction of rabbit aortic rings evoked by norepinephrine, potassium and calcium

Changrolin(CRL),4{-3’,5’-bis[(N-pyrrolidinyl) methyl]-4’-hydroxyanilino}-quinazline, is a new anti-arrhythmic drug developed in this Institute.The antagonistic effects of changrolin were examined on the isolated rabbit aortic rings evoked by norepinephrine(0.01-10 Nm), KCl(14.7-84.7 Mm) and CaCl2(0.1-3 Mm). Papsverine,verapamil and phentolamine were used as reference.CRL shifted the cumulative concentration-response curves for norepinephrine. KCl and CaCl2 to right, and depressed their maximal responses with an IC50 of 0.25,0.4 and 0.2 mM, respectively. As shown by the –logIC50,CRL was similar to papaverine but different from phentolamine and verapamil.It is suggested that CRL is not a calcium channel blocker.