MECHANISM OF ELECTRICAL STIMULATION-INDUCED SUBSENSITIVITY OF VASCULAR SMOOTH-MUSCLE

  • 1 January 1981
    • journal article
    • research article
    • Vol. 218  (2) , 382-389
Abstract
Direct electrical stimulation (DES) of the smooth muscle in the wall of the rabbit ear artery results in decreased responsiveness to subsequent exposure to norepinephrine, histamine and serotonin, but not K. DES had no effect on the transient contraction in ear arteries to histamine that were exposed to Ca-free Krebs'' solution for 5 min. Ca added in the continued presence of histamine elicited decreased tonic contractions in directly stimulated tissues. Directly stimulated everted vessels removed from surgically denervated or normal rabbits responded to norepinephrine or histamine with initial transient contractions identical to that of their respective rested everted controls. The 2nd phase tonic responses were depressed. The subsensitivity was almost completely prevented by DES in the presence of KCl or papaverine. When histamine, norepinephrine or sympathetic nerve stimulation were applied concomitantly with the DES, similar levels of subsensitivity were found. Prior electrical stimulation may decrease responsiveness by reducing the effectiveness of coupling between the agonist-receptor activation of increased Ca permeability.