Neuropeptide Y increases intracellular calcium in rat pinealocytes

The pineal gland is mainly innervated by sympathetic fibres containing nora drenaline (NA) and neuropeptide Y (NPY), NA released at night stimulates me latonin synthesis via a beta(1)-adrenergic-induced increase in cyclic adeno sine monophosphate (cAMP) concentration potentiated by an alpha(1)-adrenerg ic-induced increase in Ca2+ concentration. We previously showed that NPY ac ted on presynaptic Y2 receptors inhibiting NA release and on postsynaptic Y 1 receptors stimulating melatonin synthesis. Here we used Fura-2 imaging to assess the effect of NPY on the intracellular Ca2+ concentration, [Ca2+](i ), in cultured rat pineal cells. In 84% of cells, on average, 10 nM NPY ind uced a progressive rise of [Ca2+](i) from its basal value of 102 +/- 3 nM t o a plateau of 180 +/- 6 nM (n = 467 cells), which lasted the time of NPY a pplication. This effect of NPY appeared dependent on extracellular Ca2+.