The modulatory effects of neuropeptide Y (NPY) on ATP-induced increases in cytosolic free-calcium concentration ([Ca2+]i) were investigated in the CHP-234 human neuroblastoma cell line. Pretreatment of cells with 100 nM NPY potentiated the increase in [Ca2+]i evoked subsequently by 20 ƁM ATP, compared with initial application of ATP in a control experiment, whereas a similar pretreatment with 1 ƁM NPY attenuated the subsequent response to ATP. Both actions of NPY were completely blocked by H-89 {N-[2-((3-(4-bromo-phenyl)-2-propenyl)-amino)-ethyl]-5 isoquinoline sulphonamide dihydrochloride}, a selective antagonist of protein kinase A. The effects of 100 nM NPY were mimicked by H-89, while forskolin and 8-Br-cAMP mimicked the effects of 1 ƁM NPY. Both basal and forskolin-stimulated cAMP levels were inhibited by 100 nM NPY and by 100 nM NPY(13-36), a selective agonist of the NPY Y2-receptor subtype. In contrast, at 1 ƁM such inhibition was not observed for either NPY or NPY(13-36). It is concluded that NPY has a biphasic modulatory effect on increases in [Ca2+]i produced by ATP, which probably involves the cAMP/protein kinase A cascade.
Y2 receptors for neuropeptide Y are coupled to three intracellular signal transduction pathways in a human neuroblastoma cell line.
