Blockade of neuropeptide Y-induced potentiation of noradrenaline-evoked vasoconstriction by D-myo-inositol-1.2.6-trisphosphate (PP56) in rabbit femoral arteries.

Neuropeptide Y (NPY) potentiates noradrenaline (NA)-evoked constriction of circular segments of the rabbit femoral artery. The potentiation occurs exclusively in the lower concentration-range of the agonist NA (10(-8)-3 x 10(-7) M) without any change in maximum contractile effect. NPY per se is without contractile effect in the rabbit femoral artery. The recently developed substance, D-myo-inositol-1.2.6-trisphosphate (PP56), which is an isomer of inositol-1.4.5-trisphosphate, is without effect per se on the rabbit femoral artery, nor does it affect NA-induced contractions. However, it was found to completely antagonize NPY-induced potentiation of the NA concentration-response curve.