Inhibition of Ca 2+channel currents in human neuroblastoma (SH-SY5Y) cells by neuropeptide Y and a novel cyclic neuropeptide Y analogue

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Whole-cell Ca 2+channel currents were recorded in human neuroblastoma (SH-SY5Y) cells, using conventional and perforated-patch techniques. Neuropeptide Y (NPY, 10–1000 nM) caused concentration-dependent inhibition of Ca channel current amplitudes which was pertussis toxin-sensitive, voltage-dependent and associated with slowing of channel activation kinetics, regardless of which recording configuration was used. Inhibition was observed in all cells tested. Similar current inhibitions were observed with NPY(18–36) and peptide YY, but not with [Leu 31, Pro 34]NPY, indicating that the effects were mediated by Y 2 receptors. Pancreatic polypeptide (100 nM) was without effect on Ca 2+ channel currents. The effects of NPY were additive with nifedipine (at a supramaximal concentration of 5 μM), suggesting that NPY predominantly inhibits N-type Ca 2+ channels present in these cells, and not L-type. The effects of NPY were mimicked by a novel, cyclic analogue of NPY which is 40-fold more selective for Y 2 receptors than other commonly used Y 2-selective peptides. The cyclic analogue was also more potent than NPY itself, causing maximal current inhibition at approx 300 nM, whereas the response to NPY was not fully saturated at 1 μM. Our results indicate that SH-SY5Y cells represent an excellent model system for studying the coupling of Y 2 receptors to N-type channel inhibition. Furthermore, in the absence of selective antagonists for NPY receptor subtypes, the highly selective Y 2 agonist cyclic NPY derivative may prove a useful tool for probing the various roles of Y 2 receptors in the nervous system.