ROLE OF NEURAL PLASTICITY IN PUBERTY

这个项目的长期目标是了解触发人类青春期的机制。在人类和其他高等灵长类动物中，下丘脑GnRH脉冲产生系统在婴儿期起作用，该系统在成人中为垂体-性腺轴提供主要驱动。然而，在青春期前发育期间，控制灵长类性腺功能的神经内分泌轴的活动被下丘脑GnRH脉冲发生器的非性腺抑制所抑制并保持在长期的静止状态。因此，灵长类动物的青春期是由GnRH脉冲发生器活动的重新唤醒引发的。这种青春期控制系统似乎是人类、猿类和猴子所独有的。尽管青春期是人类发展的一个重要里程碑，它与行为、认知功能、前景以及在某些情况下与情感障碍的发病有关，但人们对这一发育阶段发病的基本神经生物学知之甚少。这个问题将在本提案中解决，使用雄性恒河猴，一个代表性的高等灵长类动物，作为实验范例。具体目的1 -验证以下假设：在青春期前发育过程中，中基底下丘脑（MBH） NPY张力的增加是抑制脉动性GnRH释放的关键组成部分；特异性目的2 -确定在从青少年到青春期过渡期间丢失的GnRH核周突触输入的表型；具体目的3 -确定除细胞体和树突外，GnRH网络在中隆起水平的结构重塑是否与青春期搏动性GnRH释放增加的开始有关；特异性目的4 -确定在青春期前发育阶段结束时抑制GnRH神经元网络中的结构重塑是否可以阻止青春期的发生。RNAse保护试验和原位杂交将用于跟踪NPY基因表达的发育变化。蛋白水平将通过免疫印迹法测定。NPY受体拮抗剂或脑室内注射的抗体可阻断NPY在MBH中的作用。NPY的合成会被反义寡脱氧核苷酸阻断。下丘脑的结构重塑将使用光镜和电子显微镜进行研究。标准的包埋前和包埋后免疫细胞化学程序将应用于量化GnRH核周、树突和轴突末梢突触输入和胶质鞘的变化。将尝试通过在青春期下丘脑注射或过度表达神经酰胺酶来阻断该区域GnRH网络的可塑性。

The long term goal of this project is to understand the mechanisms that are responsible for triggering the onset of puberty in our own species. In man and other higher primates, the hypothalamic GnRH pulse generating system, which, in the adult, provides the principal drive to the pituitary-gonadal axis, is functional during infancy. During prepubertal development, however, activity of the neuroendocrine axis governing primate gonadal function is arrested and held in a protracted state of quiescence by non-gonadal restraint of the hypothalamic GnRH pulse generator. Puberty in primates is thus triggered by a reawakening of GnRH pulse generator activity. Such a pubertal control system appears unique to man, apes and monkeys. Although puberty represents a major landmark in human development that is associated with dramatic changes in behavior, cognitive function, outlook, and, in some cases, with the onset of affective disorders, little is known about the fundamental neurobiology underlying the onset of this developmental stage. This problem will be addressed in the present proposal using the agonadal male rhesus monkey, a representative higher primate, as an experimental paradigm. The following Specific Aims Will be addressed: Specific Aim 1 - To test the hypothesis that an increase in NPY tone in the mediobasal hypothalamus (MBH) is a critical component of the restraint that is imposed upon pulsatile GnRH release during prepubertal development; Specific Aim 2 - To determine the phenotype of the synaptic input to GnRH perikarya that is lost during the transition from the juvenile to the pubertal state; Specific Aim 3 - To determine whether structural remodeling of the GnRH network at the level of the median eminence, in addition to that at the cell body and dendrites, occurs in association with the onset of the pubertal reaugmentation of pulsatile GnRH release; Specific Aim 4 - To determine whether inhibition of structural remodeling within the GnRH neuronal network at the end of the prepubertal phase of development prevents the onset of puberty. RNAse protection assays and in situ hybridization will be used to track developmental changes in NPY gene expression. Protein levels will be determined by Western blotting. The action of NPY in the MBH will be blocked using NPY receptor antagonists or antibodies administered intracerebroventricularly. Synthesis of NPY will be blocked with antisense oligodeoxynucleotides. Structural remodeling in the hypothalamus will be studied using both the light and electron microscope. Standard pre-embedding and post-embedding immunocytochemical procedures will be applied to quantitate changes in synaptic input and glial ensheathment of GnRH perikarya, dendrites and axonal terminals. Attempts will be made to block plasticity in the GnRH network of the pubertal hypothalamus by injecting or overexpressing endoneuraminidase in this region of the brain.