Mechanism of the potentiation of vasoconstriction by neuropeptide Y in arterioles from the submucosa of the guinea-pig small intestine

1. Neuropeptide Y (NPY; 3-100 nmol/L) caused a concentration-dependent potentiation of constriction in response to noradrenaline or the thromboxane mimetic U46619 in arterioles from the submucosa of the guinea-pig small intestine. 2. In arterioles permeabilized by exposure to the alpha-toxin of Staphylococcus aureus and maintained in Ca2+-buffered medium, NPY potentiated the contractile effects of Ca2+. The magnitude of the potentiation was the same as in intact arterioles. 3. Exposure of arterioles to 1 mu mol/L nifedipine to inhibit Ca2+ influx or to 20 mu mol/L cyclopiazonic acid to abolish Ca2+ uptake into internal stores had no effect on the potentiating action of NPY.