INHIBITION OF CA2+ CHANNEL CURRENTS IN HUMAN NEUROBLASTOMA (SH-SY5Y) CELLS BY NEUROPEPTIDE-Y AND A NOVEL CYCLIC NEUROPEPTIDE-Y ANALOG

Whole-cell Ca2+ 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 Ca2+ 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 Ca2+ channel currents. The effects of NPY were additive with nifedipine (at a supramaximal concentration of 5 mu M), suggesting that NPY predominantly inhibits N-type Ca2+ 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 mu M. 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.