NPY AND ATP COTRANMISSION IN CHROMAFFIN CELLS

神经肽Y（NPY）发挥多种作用，包括增加血压和食物摄入量以及减少焦虑。血压的升高与共存的递质如ATP和去甲肾上腺素有关。 本实验室的长期研究目标是揭示神经肽产生生理变化的机制。 牛嗜铬细胞提供了一个有用的模型，研究神经肽的作用，因为这些细胞合成和分泌神经肽Y的刺激与尼古丁。 目前建议的目标是深入了解NPY作为ATP共递质的生理作用。 NPY结合Y1亚型的嗜铬细胞受体并抑制毛喉素刺激的腺苷酸环化酶活性。 我们的初步数据表明，它不改变嗜铬细胞内Ca 2+浓度（[Ca 2 +]i）或肌醇磷酸的形成，除非ATP加入到培养基沿着与NPY。 NPY可显著增强ATP刺激的磷酸肌醇形成和[Ca ~（2+）]i的增加。 嗜铬细胞对这种作用的反应尚不清楚，但可能包括神经递质合成的调节，因为磷酸肌醇形成和[Ca 2 +]i增加可能已被证明导致酪氨酸羟化酶合成增加。 此外，[Ca 2 +]i的增加可以刺激酪氨酸羟化酶活性急剧增加，由于CaM激酶II介导的酶磷酸化。 我们的假设是，NPY和ATP是嗜铬细胞中的共递质，其通过增加磷酸肌醇的形成来增加[Ca 2 +]i，从而增加儿茶酚胺生物合成。 具体目的是表征NPY对ATP刺激的磷酸肌醇形成的增强作用，鉴定介导InsP形成刺激和[Ca 2 +]i增加的ATP受体亚型，确定NPY的ATP增强作用的特异性，并发现嗜铬细胞对细胞内Ca 2+增加的反应。 这些研究将进一步加深我们对神经肽的生理作用及其参与共传递的理解。将提供可能导致改善疾病治疗的信息，特别是涉及儿茶酚胺传递异常的疾病，癫痫厌食酗酒和高血压

Neuropeptide Y (NPY) exerts a variety of effects including increased blood pressure and food intake and decreased anxiety. The increase in blood pressure occurs in conjunction with co- existing transmitters such as ATP and norepinephrine. The long- term objective of research in this laboratory is to reveal the mechanism(s) by which neuropeptides produce physiological changes. Bovine chromaffin cells provide a useful model with which to study neuropeptide action since these cells synthesize and secrete NPY in response to stimulation with nicotine. The goal of the current proposal is to gain insight into the physiological role of NPY as a co-transmitter with ATP. NPY binds to chromaffin cell receptors of the Y1 subtype and inhibits forskolin stimulated adenylate cyclase activity. Our preliminary data show that it does not alter chromaffin cell intracellular Ca2+ concentration ([Ca2+]i) or inositol phosphate formation unless ATP is added to culture media along with NPY. NPY can significantly enhance both the ATP stimulated increase in inositol phosphate formation and [Ca2+]i. The chromaffin cell response to this action is unknown but may include the regulation of neurotransmitter synthesis since increased inositol phosphate formation and [Ca2+]i could have been shown to result in increased tyrosine hydroxylase synthesis. In addition, an increase in [Ca2+]i could stimulate tyrosine hydroxylase activity acutely due to increased enzyme phosphorylation mediated by CaM kinase II. Our hypothesis is that NPY and ATP are co- transmitters in chormaffin cells that serve to increase [Ca2+]i by increasing inositol phosphate formation with the resultant effect of increased catecholamine biosynthesis. The specific aims are to characterize the enhancing effect of NPY on ATP- stimulated inositol phosphate formation, identify the ATP receptor subtype mediating the stimulation of InsP formation and increased [Ca2+]i, determine the specificity of the ATP potentiating effect of NPY and discover the response of the chromaffin cell to increased intracellular Ca2+. These studies will further our understanding of the physiological role of neuropeptides and their involvement in co-transmission. Information will be provided which may lead to improved therapy of diseases particularly involving aberrations in transmission by catecholamines e.g., epilepsy, anorexia, alcoholism, and hypertension.