NEUROPEPTIDE-Y ELEVATES INTRACELLULAR CA2-SY5Y CELLS( AND EVOKES NORADRENALINE RELEASE IN SH)

EXPOSURE of human neuroblastoma SH-SY5Y cells to 300 nM neuropeptide Y (NPY) or 1 mu M muscarine separately failed to evoke release of [H-3] noradrenaline ([H-3]NA). Both agonists, however, induced a modest rise in [Ca2+](i). When NPY and muscarine were applied simultaneously, the rise in [Ca2+](i) was greater than the sum of the rises of either ago nist applied alone, and also evoked [H-3]NA release. NPY evoked a rise in [Ca2+](i) when applied during prolonged exposure to muscarine, alt hough the peak level of [Ca2+](i) was significantly lower (p<0.05) tha n that reached following simultaneous application, and [H-3]NA release was not stimulated. Simultaneous exposure of SH-SY5Y cells to muscari ne and NPY thus induces a greater than additive rise in [Ca2+](i) exce eding a critical level required to evoke [H-3]NA release.