LOCAL SYNAPTIC INTERACTIONS AMONG HYPOTHALAMIC NEURONS

在激素分泌增加的条件下（例如，期间 生殖功能），下丘脑神经分泌神经元 室旁核（PVN）发展的特征模式， 电活动和神经激素释放。 这些模式 激活也是由本征电性质决定的 就像分泌突触的细胞一样。 当地 突触回路对于产生模式化的电 活动，但对局部突触调节知之甚少 神经分泌神经元。 本研究的长期目标是 从生理学和解剖学上表征局部突触 PVN大细胞和小细胞神经元的组织，以及 确定局部突触输入如何调节电活动， PVN神经元的激素/突触输出。 具体目标是 建议是：（1）描述地形特征并绘制地形图 从PVN外的细胞到PVN神经元的局部突触输入，2） 确定PVN大细胞和小细胞神经元是否 突触耦合和递质或激素介导这些 相互作用，以及3）在解剖学上识别PVN的细胞群 接收局部突触输入。 在此期间， 实验中，我们将确定局部突触输入对 识别的PVN细胞的电活动。 实验将 在大鼠下丘脑切片中使用细胞内、全细胞 PVN细胞的膜片钳和细胞外记录。 细胞将被 根据它们的大小， 细胞内电特性 谷氨酸微量应用 将用于选择性刺激局部神经元， 包含细胞的PVN内和PVN外区域的映射， 抑制性和/或兴奋性突触输入到记录的PVN神经元。 结论性证明PVN细胞和局部神经元之间的突触耦联 中间神经元（PVN和非PVN）将通过配对 动作电位和突触的记录和互相关 活动 将应用特异性拮抗剂来确定 递质和递质受体介导这些局部突触 交互. 激活局部突触输入对神经元突触活动的影响 PVN细胞的模式化活性（例如，加压素时相放电 细胞）进行分析。 所有细胞内/膜片钳记录细胞 将被细胞内标记，并用 针对一般神经垂体后叶素的抗体（以区分 大细胞和小细胞神经元），催产素，加压素或 促肾上腺皮质激素释放激素。 这些结合了电生理学- 解剖学研究将阐明局部突触组织的 下丘脑PVN，并将提供有关调节的生理数据 PVN细胞的输出由局部突触输入。

Under conditions of increased hormone secretion (e.g., during reproductive functions), neurosecretory neurons in the hypothalamic paraventricular nucleus (PVN) develop characteristic patterns of electrical activity and neurohormone release. These patterns of activation are determined by the intrinsic electrical properties as well as by the synaptic organization of the hormone-secreting cells. Local synaptic circuits are crucial for the generation of patterned electrical activity, yet very little is known about the local synaptic regulation of neurosecretory neurons. The long-term objectives of this study are to characterize physiologically and anatomically the local synaptic organization of PVN magnocellular and parvocellular neurons, and to determine how local synaptic inputs regulate the electrical activity and hormonal/synaptic output of PVN neurons. The specific aims of this proposal are 1) to characterize pharmacologically and map topographically local synaptic inputs to PVN neurons from cells outside the PVN, 2) to determine whether PVN magnocellular and parvocellular neurons are synaptically coupled and the transmitters or hormones which mediate these interactions, and 3) to identify anatomically cell populations of the PVN which receive local synaptic inputs. During the course of these experiments, we will determine the effects of local synaptic inputs on the electrical activity of identified PVN cells. Experiments will be performed in rat hypothalamic slices using intracellular, whole-cell patch-clamp and extracellular recordings of PVN cells. Cells will be identified provisionally as magnocellular or parvocellular by their intracellular electrical characteristics. Glutamate microapplication will be used to stimulate selectively local neurons for topographic mapping of intra- and extra-PVN regions containing cells which provide inhibitory and/or excitatory synaptic inputs to recorded PVN neurons. Conclusive demonstration of synaptic coupling between PVN cells and local interneurons (PVN and non-PVN) will be accomplished with paired recordings and cross-correlation of action potentials and synaptic activity. Specific antagonists will be applied to determine the transmitters and transmitter receptors which mediate these local synaptic interactions. The effect of activation of local synaptic inputs on the patterned activity of PVN cells (e.g., phasic firing of vasopressin cells) will be analyzed. All intracellular/patch-clamp-recorded cells will be intracellularly labeled and immunohistochemically identified with antibodies directed against general neurophysin (to distinguish between magnocellular and parvocellular neurons), oxytocin, vasopressin or corticotropin-releasing hormone. These combined electrophysiological- anatomical studies will elucidate the local synaptic organization of the hypothalamic PVN, and will provide physiological data on the regulation of PVN cell output by local synaptic inputs.