Neuropeptide Y elevates intracellular Ca2+ and evokes noradrenaline release in SH-SY5Y cells

EXPOSURE of human neuroblastoma SH-SY5Y cells to 300 nM neuropeptide Y (NPY) or 1 μM muscarine separately failed to evoke release of [H]noradrenaline ([H]NA). Both agonists, however, induced a modest rise in [Ca]i. When NPY and muscarine were applied simultaneously, the rise in [Ca]i was greater than the sum of the rises of either agonist applied alone, and also evoked [H]NA release. NPY evoked a rise in [Ca]i when applied during prolonged exposure to muscarine, although the peak level of [Ca]i was significantly lower (p < 0.05) than that reached following simultaneous application, and [H]NA release was not stimulated. Simultaneous exposure of SH-SY5Y cells to muscarine and NPY thus induces a greater than additive rise in [Ca]i exceeding a critical level required to evoke [H]NA release.