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

Abstract

Background and PurposeRaised 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 ApproachThird‐order mesenteric or intra‐septal arteries from male Wistar rats were assessed in wire myographs for isometric tension, VSM membrane potential and VSM intracellular Ca2+ events.Key ResultsNPY stimulated concentration‐dependent vasoconstriction in both RMA and RCA, which was augmented by blocking NO synthase or endothelial denudation in RMA. NPY‐mediated vasoconstriction was blocked by the selective Y1 receptor antagonist BIBO 3304 and Y1 receptor protein expression was 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 generation of action potential‐like spikes associated with intense vasoconstriction. This depolarization activated L‐type voltage‐gated Ca2+ channels, as nifedipine abolished NPY‐mediated vasoconstriction.Conclusions and ImplicationsThese data suggest that the Gβγ subunit, which dissociates upon Y1 receptor activation, initiates VSM membrane depolarization and Ca2+ mobilisation to cause vasoconstriction. This model may help explain the development of microvascular vasospasm during raised sympathetic nerve activity.

Asymmetric Dimethylarginine Enables Depolarizing Spikes and Vasospasm in Mesenteric and Coronary Resistance Arteries

“…Endothelium-dependent mesenteric artery vasorelaxation is mediated by the parallel action of both NO and EDH, the latter generated by dual activation of EC SK Ca and IK Ca channels. Subsequent block of EDH with 1 µmol/L NS6180 (blocks EC IK Ca channels, K Ca 3.2 22 ) combined with 0.1 µmol/L apamin (blocks endothelial SK Ca channels, K Ca 2.1) abolished EDH hyperpolarization and vasorelaxation in the presence of L-NAME. However, vasorelaxation persisted with ADMA and NS6180/apamin present, even though hyperpolarization was abolished (Figure 2 C through 2 F).…”