Gβγ subunit signalling underlies neuropeptide-Y-stimulated vasoconstriction in rat mesenteric and coronary arteries.

BACKGROUND AND PURPOSE: Raised serum concentrations of the sympathetic co-transmitter neuropeptide Y (NPY) are linked to cardiovascular diseases. However, the signalling mechanism for vascular smooth muscle (VSM) constriction to NPY is poorly understood. Therefore, the present study investigated the mechanisms of NPY-induced vasoconstriction in rat small mesenteric (RMA) and coronary (RCA) arteries. EXPERIMENTAL APPROACH: Third order mesenteric or intra-septal arteries from male Wistar rats were assessed in wire myographs for isometric tension, VSM membrane potential, VSM intracellular Ca2+ events. KEY RESULTS: NPY stimulated concentration-dependent vasoconstriction in both RMA and RCA, which was augmented by blocking NO synthase or denuding the endothelium in RMA. NPY-mediated vasoconstriction was blocked by the selective Y1 receptor (Y1 R) antagonist BIBO 3304, and Y1 R protein expression detected in both the VSM and endothelial cells in RMA and RCA. The selective Gβγ subunit inhibitor gallein and the PLC inhibitor U-73122 attenuated NPY-induced vasoconstriction. Signalling via the Gβγ-PLC pathway stimulated VSM Ca2+ waves and whole-field synchronised Ca2+ flashes in RMA, and increased the frequency of Ca2+ flashes in myogenically-active RCA. Furthermore, in RMA, the Gβγ pathway linked NPY to VSM depolarization and the generation of action potential-like spikes associated with intense vasoconstriction. This depolarization activated L-type voltage-gated Ca2+ channels, as NPY-mediated vasoconstriction was abolished by nifedipine. CONCLUSIONS AND IMPLICATIONS: The present data suggest that the Gβγ subunit, which dissociates upon Y1 R activation, initiates VSM membrane depolarization and Ca2+ mobilization to cause vasoconstriction. This model may help explain the development of microvascular vasospasm during raised sympathetic nerve activity.