Neuropeptide Y (NPY) participates in the control of several functions in the nervous system. NPYergic neurons present in brain areas involved in cognitive processes are linked to ascending projections of the cholinergic system, a finding that suggests a role for acetylcholine in the control of these cells. In the present study, the effect of the activation of cholinergic muscarinic receptors on the expression of the human NPY gene was assessed. The SH-SY5Y neuroblastoma cell line was used as an in vitro model of human neurons; NPY mRNA levels were evaluated by Northern blot analysis. The results indicate that: (a) the expression of the human NPY gene in SH-SY5Y cells is stimulated by the cholinergic muscarinic agonist, carbachol; (b) this effect is mediated by the M3 muscarinic receptor subtype, as indicated by the inhibitory effect of the M3 antagonist 4-DAMP; (c) protein kinase C (PKC) activation plays an important role in the induction of NPY gene expression in this system, as suggested by experiments with the PKC activator, TPA, and the PKC inhibitor, GF 109203X; (d) the stimulation of NPY mRNA levels by TPA and by carbachol in SH-SY5Y cells requires de novo synthesis of RNA and protein. In conclusion, the present study shows that the activation of PKC-coupled muscarinic receptors as the M3 subtype positively modulates the expression of the human NPY gene in SH-SY5Y neuroblastoma cells, via PKC-related mechanisms.
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