DIOXINS AND HYPOTHALAMIC APPETITE NEUROPEPTIDES

这个小补助金的主要假设是，发育暴露（即围产期）多氯芳烃（PCAH）或PCAH的混合物破坏了中央控制的喂养行为。 多氯二苯并对二恶英（PCDDs）、联苯（PCBs）和二苯并呋喃（PCDFs）等多环芳烃是一类广泛分布的异生物质，具有较长的生物半衰期和生物累积潜力。他们丰富的人乳和强大的神经发育毒性，包括生长迟缓，在围产期暴露于PCAH的混合物的儿童被记录。 毒性最大的PCAH是（2，3，7，8-四氯二苯并对二恶英）或TCDD。TCDD是一种非常有效的促生长剂和致瘦剂;在动物研究中，PCAH暴露的一个标志是“消耗综合征”，包括生长速度下降和摄食量减少。PCAH对摄食行为的抑制作用的潜在毒性机制和作用部位尚不清楚。我们提出的假设，在控制摄食行为的下丘脑中心的神经肽的动态平衡的破坏，发育暴露于PCAH，是PCAH诱导的食欲减退的机制。 我们将首先测量在妊娠期间或在妊娠和哺乳期间给予TCDD对下丘脑两种刺激性神经肽（神经肽Y（NPY）和黑色素浓集激素（MCH））和两种抑制性神经肽（α-黑色素细胞刺激激素（α-MSH）和促肾上腺皮质激素释放激素（CRH））表达的影响。 如果我们没有观察到单独的TCDD对妊娠或妊娠加哺乳实验中提出的一种或多种下丘脑神经肽的影响，我们将测试由2，3，7，8-TCDD、2，3，7，8-TCDF、1，2，3，7，8-PeCDD、1，2，3，7，8-PeCDF、2，3，4，7，8-PeCDF、OCDF组成的PCAH混合物的影响，以及在妊娠期或妊娠期和哺乳期给予的PCBs 77、126和169。 我们将测量其他参与食物摄入调节的下丘脑神经肽的表达，如甘丙肽、刺豚鼠相关肽和食欲素。我们将通过北方和狭缝印迹分析和放射免疫分析来测量PCAH对显微解剖的下丘脑区域中神经肽表达的影响。 如果我们发现下丘脑神经肽的表达水平的变化并不构成PCAH治疗期间PCAH诱导的食欲减退的基础，我们将检验另一种假设，即PCAH破坏下丘脑NPY、食欲素和α-MSH受体的表达。 我们的目的是证明参与下丘脑摄食行为控制的神经肽或神经肽受体的稳态改变是PCAH的厌食作用的一种机制。

The primary hypothesis for this small grant is that developmental exposure (ie, perinatal) to PolyChlorinated Aromatic Hydrocarbons (PCAHs) or to mixtures of PCAHs disrupts the central control of feeding behavior. PCAHs, such as polychlorinated dibenzo-rho-dioxins (PCDDs), biphenyls (PCBs) and dibenzofurans (PCDFs) represent a diverse group of widespread xenobiotics with long biological half lives and potential for bioaccumulation. Their abundance in human milk and potent neurodevelopmental toxicity, including growth retardation, in children exposed perinatally to mixtures of PCAHs is documented. The most toxic of the PCAHs is (2,3,7,8-tetrachlorodibenzo-rho-dioxin) or TCDD. TCDD is an exceedingly potent anorexic and leptogenic agent; a hallmark of PCAH exposure in animal studies is the " wasting syndrome" which includes depressed growth rates and hypophagia. The underlying mechanism(s) of toxicity and site of action for the inhibitory action of PCAHs on feeding behavior is not known. We propose the hypothesis that disruption in the homeostasis of neuropeptides in hypothalamic centers that control ingestive behavior, by developmental exposure to PCAHs, is a mechanism for PCAH-induced hypophagia. We will initially measure the effects of TCDD given either during gestation or during both gestation and lactation on hypothalamic expression of two stimulatory neuropeptides: neuropeptide Y (NPY) and melanin-concentrating hormone (MCH) and of two inhibitory neuropeptides: alpha-melanocyte-stimulating hormone (alpha-MSH) and corticotrophin-releasing hormone (CRH). If we do not observe an effect(s) of TCDD alone on one or more of the of hypothalamic neuropeptides as proposed in either the gestation or gestation plus lactation experiments, we will then test the effects of a mixture of PCAHs composed of 2,3,7,8-TCDD, 2,3,7,8-TCDF,1,2,3,7,8-PeCDD, 1,2,3,7,8-PeCDF, 2,3,4,7,8-PeCDF, OCDF, and PCBs 77, 126 and 169 given either during gestation or during gestation and lactation. We will measure expression of other hypothalamic neuropeptides involved in regulation of food intake such as galanin, agouti-related peptide and the orexins. We will measure the effects of PCAHs on neuropeptide expression in micro-dissected hypothalamic regions by means of Northern and slot blotting analyses and by radioimmunoassays. If we find that changes in expression levels of hypothalamic neuropeptides do not underlie the PCAH-induced hypophagia during PCAH treatment, we will test an alternate hypothesis that PCAHs disrupt hypothalamic expression of receptors for NPY, orexins and alpha-MSH. We intend to demonstrate that alteration in the homeostasis of neuropeptides or of neuropeptide receptors involved in hypothalamic control of feeding behavior is a mechanism underlying the anorectic action of PCAHs.