The contraction of the isolated rabbit renal arteries induced by noradrenaline, high K+ & calcium could be relaxed by berbamine ( BA ). BA shifted dose-response curve of noradrenaline, high K+ snd calcium to the right, but the maximal response was reduced. The antagonistic parameter pD' 2 of berbamine on calcium contrac-tion was 4.76, which is similar to the verapamil (pD'2=5.68). Therefore berbamine can be considered as a non-competitive calcium antagonist.

The study showed that NMBA could inhibit the rabbit thoracic aorta contractions induced by KC1, CaCl2 and NA, and the pD' 2 values were 3.44, 3.67 and 3.73 respectively. NMBA could also antagonize the extracellular Ca2 + contraction of NA with no effect on the intra-cellular Ca2+ contraction. Comparing with verapamil, the mechanism of NMBA action was inferred to blocking Ca2+ influx during excitation. However, further study will be needed.