ROLE OF BDNF IN THE PHOTIC CONTROL OF CIRCADIAN RHYTHMS

这项拟议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。最近的发现表明，神经营养素，脑源性神经营养因子(BDNF0)，增强了大脑其他区域的神经元信号。我们的中心假设是，BDNF通过调节光输入及其对昼夜节律调和机制的影响，在SCN中发挥类似的作用。为了解决这一假说，拟议的研究将确定：支配SCN的视黄醇下丘脑束(RHT)纤维或接受RHT输入的细胞是否表达BDNF的同源受体TrkB酪氨酸激酶受体，使用免疫组织化学和束追踪方法，以及BDNF和TrkB表达的变化或抑制啮齿动物SCN中的BDNF作用是否会导致可预测的变化，光的相移效应对车轮运行行为的昼夜节律的影响。实验将被用来确定：1)通过电子和/或光学显微镜观察到TrkB受体在腹侧SCN的免疫反应性在RHT纤维或接受RHT神经支配的细胞上的定位，并在致盲后减弱；2)向SCN内注入外源BDNF使光在主观白天引起相移，而蝉的调和者通常对光不敏感；3)在杂合敲除小鼠(BDNF+/-和TrkB+/-)中BDNF和TrkB的转基因缺陷减弱了主观夜晚光的相移效应；4)向光的相移效应中注入酪氨酸激酶抑制剂K252a；5)给予TrkB-Ig G融合蛋白，清除内源性BDNF，类似地阻断光诱导的相移。这些研究将为BDNF在调节光对SCN和平缔造者的影响中所起的作用提供关键支持。鉴于它有可能提高我们对昼夜节律如何受光以时间依赖的方式调节的知识，这项研究已经应用于开发治疗、诊断和理解人类心理健康和表现障碍的策略，这些障碍是由身体过程的内部去同步引起的，包括情感障碍、痴呆症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.