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  • Title: The alpha 1-agonist phenylephrine inhibits voltage-gated Ca2(+)-channels in vascular smooth muscle cells of rabbit ear artery.
    Author: Declerck I, Himpens B, Droogmans G, Casteels R.
    Journal: Pflugers Arch; 1990 Sep; 417(1):117-9. PubMed ID: 1963492.
    Abstract:
    The effects of the alpha 1-agonist phenylephrine on the voltage-gated Ca2(+)-entry in vascular smooth muscle cells has been studied by measuring the agonist-induced changes of [Ca2+]i in K(+)-depolarized tissues. These changes have been estimated from the changes in fluorescence of the Ca2(+)-indicator fura-2, or have been assessed from the changes in 86Rb-efflux rate through Ca2(+)-activated K(+)-channels. Phenylephrine increases the force development in K(+)-depolarized tissues, but reduces [Ca2+]i and inhibits the 86Rb-efflux rate. However, in the presence of the Ca2(+)-entry blocker verapamil, phenylephrine increases both force development and [Ca2+]i. It is concluded that phenylephrine inhibits voltage-gated Ca2(+)-channels, and also induces an influx of calcium by activating a verapamil-insensitive pathway.
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