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Mechanism of Catecholamine Synthesis Inhibition by Neuropeptide Y: Role of Ca 2+ Channels and Protein Kinases
Author(s) -
McCullough Laura A.,
Westfall Thomas C.
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67031090.x
Subject(s) - protein kinase c , depolarization , medicine , endocrinology , neuropeptide y receptor , protein kinase a , chelerythrine , chemistry , channel blocker , stimulation , biology , kinase , calcium , receptor , biochemistry , neuropeptide
We have previously demonstrated that neuropeptide Y (NPY) inhibits depolarization‐stimulated catecholamine synthesis in rat pheochromocytoma (PC12) cells differentiated to a sympathetic neuronal phenotype with nerve growth factor (NGF). The present study uses multiple selective Ca 2+ channel and protein kinase agonists and antagonists to elucidate the mechanisms by which NPY modulates catecholamine synthesis as determined by in situ measurement of DOPA production in the presence of the decarboxylase inhibitor m ‐hydroxybenzylhydrazine (NSD‐1015). The L‐type Ca 2+ channel blocker nifedipine inhibited the depolarization‐induced stimulation of DOPA production by ∼90% and attenuated the inhibitory effect of NPY. In contrast, the N‐type Ca 2+ channel blocker ω‐conotoxin GVIA inhibited neither the stimulation of DOPA production nor the effect of NPY. Antagonism of Ca 2+ /calmodulin‐dependent protein kinase (CaM kinase) greatly inhibited the stimulation of DOPA production by depolarization and prevented the inhibitory effect of NPY, whereas alterations in the cyclic AMP‐dependent protein kinase pathway modulated DOPA production but did not prevent the effect of NPY. Stimulation of Ca 2+ /phospholipid‐dependent protein kinase (PKC) with phorbol 12‐myristate 13‐acetate (PMA) did not affect the basal rate of DOPA production in NGF‐differentiated PC12 cells but did produce a concentration‐dependent inhibition of depolarization‐stimulated DOPA production. In addition, NPY did not produce further inhibition of DOPA production in the presence of PMA, and the inhibition by both PMA and NPY was attenuated by the specific PKC inhibitor chelerythrine. These results indicate that NPY inhibits Ca 2+ influx through L‐type voltage‐gated Ca 2+ channels, possibly through a PKC‐mediated pathway, resulting in attenuation of the activation of CaM kinase and inhibition of depolarization‐stimulated catecholamine synthesis.