Effects of Ca antagonists on the norepinephrine release and contractile responses of isolated canine saphenous veins to transmural nerve stimulation.

摘要: Abstract Effects of verapamil, diltiazem and nicardipine on tritium overflow contraction evoked by transmural nerve stimulation (TNS) were evaluated using canine saphenous vein strips preincubated with [3H]norepinephrine. External Ca2+ was required for both TNS. All the Ca antagonists tested significantly increased spontaneous in a concentration-dependent manner no changes basal tension. Verapamil concentrations lower than 10−5 M enhanced TNS-evoked overflow, but reduced it at 3×10−5 M, while this drug 3×10−6–3×10−B concentration-dependently inhibited contraction. Verapamil, more strongly overflow. On other hand, higher 10−6 There significant difference between inhibitions either or nicardipine. Neither increase nor appeared to be related its phosphodiesterase inhibiting activity. These results suggest that may inhibit mainly Ca2+-dependent transmitter release from adrenergic endings, whereas verapamil restricting availability postsynaptic sites highest concentration used, additional inhibition release.