Xiao–Ping Yang and Shigetoshi Chiba*
Department of Pharmacology, Shinshu University School of Medicine, Matsumoto 390–8621, Japan
*To whom correspondence should be addressed.
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 alpha1–adrenoceptors, mostly in the 2nd–one. The dose used of neuropeptide
Y (NPY) (0.01-0.1 microM) given into the preparation caused a slight but insignificant vasoconstriction. The treat–
ment with NPY at concentrations of 0.01-0.1 microM 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 (0.01-1 micromol) or noradrenaline (0.03-3 nmol) were slightly but
not significantly potentiated by 0.1 microM 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.
Keywords: Neuropeptide Y, Periarterial nerve stimulation, Sympathetic cotransmission