CELLULAR CORRELATES OF AXONAL SPROUTING

哺乳动物下丘脑大细胞神经分泌神经元 系统(MN)表现出异常旺盛的再生能力。它有 多年来一直知道它们可以再生被切断的轴突 脑垂体柄切片，这个实验室最近证明了 未受损伤的MNS神经元的轴突终末也将经历强大的 成年大鼠的代偿性发芽。在毁掉一半之后 经单侧下丘脑的下丘脑-神经垂体束 损伤，完整的对侧MNS神经元的轴突长出萌芽 使神经叶(NL)轴突数量恢复到接近正常水平 在90天内。该项目的长期目标是确定 跨国公司的哪些特点为这一点提供了基础 可塑性。 这一建议是基于我们最近的发现：(A)后叶加压素 下丘脑室旁核(VP)和催产素(OT)神经元在 发芽反应与α1和βII微管蛋白表达增加 同种异构体；以及(B)在下丘脑核发生了短暂的胶质细胞激活 紧接在萌发开始之前，同时连续 血管生成伴随着萌芽。这项建议的具体目的 是：(1)检验神经元活动增加的假设 促进侧支的萌发，而活动减少则抑制侧支的萌发。 这将通过关联神经活动来实现，由 VP和OT基因表达、神经分泌和细胞的测量 幼年和成年大鼠的代谢与轴突萌发程度的关系 在不同的渗透条件下会改变神经分泌活动； (2)验证MNS神经元侧枝萌发假说 需要上调α1、βII和βIII微管蛋白mRNAs。这 将使用原位杂交(ISHH)来关联 MRNA池的相对变化与侧枝萌发的程度； 以及(3)检验假设碱性成纤维细胞生长因子(BFGF)， 由MNS中不同类型的细胞产生并作用于该细胞，用于 刺激和协调轴突萌发和相关的血管生成 民族解放阵线。这将使用ISHH和ICC技术来实现 碱性成纤维细胞生长因子及其高亲和力受体的表达 轴突萌发过程中的MN和相关的血管生成。履行 这些目标将提供对基本细胞机制的新见解 用中枢肽能确定侧支发芽的程度 神经元。因为几乎所有的神经紊乱都涉及到某种程度的 组织退化，增加了对潜在细胞生物学的了解 对中枢神经系统损伤的代偿性反应对于最终的 设计有效的治疗方法。

The neurons of the mammalian hypothalamic magnocellular neurosecretory system (MNS) exhibit unusually vigorous regenerative capabilities. It has been known for many years that they can regenerate axons severed by pituitary stalk section, and this laboratory has recently demonstrated that the axon terminals of uninjured MNS neurons will also undergo robust compensatory sprouting in the adult rat. Following destruction of one half of the hypothalamo-neurohypophysial tract via a unilateral hypothalamic lesion, axons of intact contralateral MNS neurons grow sprouts which return the axon population of the neural lobe (NL) to near normal levels within 90 days. The long-term objective of this project is to determine what special characteristics of the MNS provide the basis for this plasticity. This proposal builds upon our recent findings that (a) both vasopressin (VP) and oxytocin (OT) neurons appear to be hyperactivated during the sprouting response and increase expression of alpha1 and betaII tubulin isoforms; and (b) that transient glial activation occurs in the NL immediately prior to the initiation of sprouting, while continuous angiogenesis accompanies sprouting. The Specific Aims of this proposal are: (1) to test the hypothesis that increased neuronal activity facilitates collateral sprouting, whereas decreased activity inhibits it. This will be accomplished by correlating neuronal activity estimated by measures of VP and OT gene expression, neurosecretion, and cellular metabolism with the extent of axonal sprouting in juvenile and adult rats under different osmotic conditions known to alter neurosecretory activity; (2) to test the hypothesis that collateral sprouting by MNS neurons requires upregulation of alpha1, betaII, and betaIII tubulin mRNAs. This will be accomplished using in situ hybridization (ISHH) to correlate relative changes in mRNA pools with the extent of collateral sprouting; and (3) to test the hypothesis that basic Fibroblast Growth Factor (bFGF), produced by and acting upon different cell types in the MNS, serves to stimulate and coordinate axonal sprouting and associated angiogenesis in the NL. This will be accomplished using ISHH and ICC techniques to detect expression of bFGF and its high affinity receptor FGF-R by cells of the MNS during axonal sprouting and correlated angiogenesis. Fulfillment of these aims will provide new insights into basic cellular mechanisms which determine the extent of collateral sprouting by central peptidergic neurons. Since virtually all neural disorders involve some degree of tissue degeneration, increased knowledge of the cell biology underlying compensatory responses to injury of the CNS is crucial for the ultimate design of effective therapies.