Comparison of effects of four vasodilators on contractions induced by norepinephrine, KCI, and CaC12 in isolated rabbit aortic strips

The effects of phentolamine (Phe), papaverine (Pap), sodium nitroprusside (SNP), and verapamil (Ver) on contractions induced by norepinephrine (NE), KCI. and CaCl2 were compared in isolated rabbit aortic strips. The action potencies of the 4 vasodilators on contractions induced by NE I vmol/L and CaCl2 3 mmol/L were Phe> SNP> Ver> Pap. and Ver>Phe>SNP>Pap. respectively. The action of SNP on the contractions induced by NE, KCI, and CaCl2 were quite distinct from that of Pap. Phe markedly inhibited the contractions induced by KCI and CaCl2. Besides, Phe antagonized the contraction inducs by NE in a competitive way. It suggests that the action of Phe may be related to the blockade of calcium entry.