ROLE OF BDNF IN THE PHOTIC CONTROL OF CIRCADIAN RHYTHMS

拟议的研究的广泛目标是深入了解哺乳动物昼夜节律生物学的一个新领域：神经营养因子在SCN蝉功能中的作用。最近的研究表明，神经营养因子，脑源性神经营养因子（BDNF 0），增强在其他大脑区域的神经元信号。我们的中心假设是，BDNF在SCN中通过调节光输入及其对昼夜节律调解机制的影响发挥类似的作用。为了解决这一假设，拟议的研究将确定：无论支配SCN的视网膜下丘脑束（RHT）纤维还是接受RHT输入的细胞表达TrkB酪氨酸激酶受体，BDNF的同源受体，使用免疫组化和束示踪方法，以及BDNF和TrkB表达的改变或BDNF作用的抑制是否在啮齿动物SCN中产生可预测的时相变化，光对车轮运行行为的昼夜节律的影响。将进行实验以确定：1）通过电子和/或光学显微镜在RHT纤维或接受RHT神经支配的细胞上观察到腹侧SCN中TrkB受体免疫反应性的定位，并且在致盲后减弱; 2）将外源性BDNF输注到SCN中使得光能够在蝉和平使者通常对光不敏感的主观白天期间诱导相移; 3）杂合敲除小鼠中BDNF和TrkB表达的转基因缺陷（bdnf+/-和trkB+/-）减弱光在主观夜间的相移效应：4）向光的相移效应中注入酪氨酸激酶抑制剂K252 a; 5）施用清除内源性BDNF的TrkB-IgG融合蛋白类似地阻断光诱导的相移。这些研究将为BDNF在调节光对SCN和平使者的影响中的作用提供关键支持。鉴于它有可能促进我们对昼夜节律如何以时间依赖性方式受光调节的认识，本研究已应用相关性来制定治疗，诊断和理解人类心理健康和表现障碍的策略，这些障碍是由于身体过程的内部去极化导致的，包括情感障碍，痴呆和衰老期间的生理衰退。

The broad objective of the proposed research is to gain insight into a new area in mammalian circadian biology: the role of neurotrophins in SCN cicadian function. Recent findings indicate that the neurotrophin, brain- derived neurotrophic factor (BDNF0, enhances neuronal signaling in other brain regions. Our central hypothesis is that BDNF plays a comparable role in the SCN by regulating photic input and its effects on the circadian peacemaker mechanism. To address this hypothesis, the proposed studies will determine: whether retinohypothalamic tract (RHT) fibers innervating the SCN or cells receiving RHT input express TrkB tyrosine kinase receptors, the cognate receptor for BDNF, using imunochistochemical and tract tracing methods and whether alterations in BDNF and TrkB expression or inhibition of BDNF action in the rodent SCN produce predictable changes in the phase-shifting effect of light on the circadian rhythm of wheel-running behavior. Experiments will be conducted to determine whether: 1) localization of TrkB receptor immuno reactivity in the ventral SCN by electron and/or light microscopy is observed on RHT fibers or on cells receiving RHT innervation and is diminished after blinding; 2) infusion of exogenous BDNF into the SCN enables light to induce phase shifts during the subjective day when the cicadian peacemaker is normally insensitive to light; 3) transgenic deficits in BDNF and TrkB expression in heterozygous knock-out mice(bdnf+/- and trkB+/-) abate the phase-shifting effect of light during the subjective night; 4) infusion of the tyrosine kinase inhibitor, K252a, into the phase-shifting effect of light; 5) administration of TrkB-IgG fusion protein, which scavenges endogenous BDNF, similarly blocks light-induced phase shifts. These studies will purvey critical support of the role of BDNF in regulating the effects of light on the SCN peacemaker. In view of it's potential to advance our knowledge of how circadian rhythms are regulated by light in a time-dependent manner, this research has applied relevance for developing strategies in the treatment, diagnosis and understanding of disorders in human mental health and performance that result from internal desynchronization of body process, including affective disorders, dementia and physiological decline during aging.