Abstract
The periarterial electrical nerve stimulation readily induced a double−peaked vasoconstriction in the isolated, perfused canine splenic artery.P2X−Purinoceptors have previously been shown to be involved mainly in the 1st−phase response and α1−adrenoceptors, mostly in the 2nd−one.The dose used of neuropeptide Y(NPY)(0.01−0.1μM)given into the preparation caused a slight but insignificant vasoconstriction.The treatment with NPY at concentrations of 0.01−0.1μM produced a parallel inhibition on the 1st− and 2nd−phase responses following nerve stimulation at the frequencies used(1−10 Hz)in a dose−dependent manner.The vasoconstrictor responses to administered ATP(0.01−1μmol)or noradrenaline(0.03−3 nmol)were slightly but not significantly potentiated by 0.1μM NPY.The results indicate that NPY predominantly exerts a prejunctionally inhibitory modulation on the purinergic and adrenergic transmission in peripheral sympathetic nerves innervating the canine splenic artery.
