EFFECTS OF VERAPAMIL ON [H-3]NOREPINEPHRINE RELEASE

  • 1 January 1984
    • journal article
    • research article
    • Vol. 6  (6) , 1060-1066
Abstract
If Ca2+ entry blocking drugs affect norepinephrine release, this may alter their cardiovascular action by modifying the activity of baroreceptor reflexes. The effect of verapamil on 3H-release was studied in [3H]norepinephrine-incubated rat arteries and guinea pig vas deferens. Superfusion of tail artery with verapamil (10-6-10-4 M) increased the 3H-overflow induced by transmural stimulation (1 Hz, 2 ms, 10 V) both in Wistar Kyoto and in spontaneously hypertensive rats. The effect was present also in vessels pretreated with cocaine to inhibit neuronal uptake or with yohimbine to block .alpha.2-adrenoceptors. The greatest increase in 3H-overflow.sbd.around 400% in the various groups.sbd.was observed after perfusion with 10-4 M verapamil. Verapamil also enhanced 3H-overflow from vessels not stimulated transmurally; this effect again was dose-related (P < 0.001). In the vas deferens of the guinea pig, 10-5 M verapamil increased spontaneous and electrical stimulation-induced 3H-release (P < 0.001), whereas superfusion of the tissue with 10-9 and 10-7 M verapamil was ineffective. Apparently, verapamil can act on sympathetic nerves to release norepinephrine.

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