Résumé
The hypothesis that neuropeptide Y (NPY) potentiates noradrenaline (NA)-induced vascular force development by increasing free intracellular Ca 2+ ([Ca 2+ ] i ) was tested in rat mesenteric resistance arteries. NPY (100 nM) alone was not able to increase either the contraction or [Ca 2+ ] i . However, pretreatment of mesenteric resistance arteries with 100 nM NPY potentiated both [Ca 2+ ] i and active stress induced by 1.5 µM NA. Addition of 100 nM NPY to vessels that had been precontracted with NA (1.5 µM) elicited a large increase in [Ca 2+ ] i and an increase in active stress development. In Ca 2+ -free medium containing 2 mM ethylene glycol-bis(β-aminoethyl ether) NNN’N’-tetraacetic acid, the potentiating effect of NPY on the NA-induced contraction was prevented, and readdition of Ca 2+ resulted in a large increase in both [Ca 2+ ] i and active stress development. It is concluded that NPY potentiates NA-induced contraction in the isolated mesenteric resistance artery by inducing a rise in [Ca 2+ ] i through an influx of Ca 2 from the extracellular source.