Long lasting increase in neuropeptide Y gene expression in rat adrenal gland with reserpine treatment: positive regulation of transsynaptic activation and membrane depolarization.

To elucidate how the neuropeptide Y (NPY) gene is regulated by physiological/pharmacological changes in neural functions, the expression and regulation of the NPY gene were studied by measuring changes in the abundances of NPY and NPY mRNA in the adrenal gland and brain regions of rats in vivo and in PC12 rat pheochromocytoma cells after reserpine treatment. Long term treatment with reserpine in vivo, which causes hypotension and increased splanchnic nerve activity, induced prolonged increases in the abundance of NPY mRNA and putative NPY pre-mRNA, with concomitant increases in NPY, in the adrenal gland in a tissue-dependent manner but caused no changes in the abundance of beta-actin mRNA. Transection of the splanchnic nerves almost completely (76%) prevented the reserpine-induced increases in the abundance of NPY mRNA and NPY pre-mRNA, but denervation alone did not affect their steady state levels. These results suggested that increased activity of the splanchnic nerves regulates NPY gene expression positively in the adrenal gland, probably at the level of transcription. In PC12 cells, reserpine decreased the abundance of NPY mRNA directly, but nicotinic receptor activation increased its abundance transiently and the persistent membrane depolarization increased its abundance markedly. Thus, NPY gene expression is positively regulated by membrane depolarization via increased transsynaptic activation with reserpine.