LOCAL SYNAPTIC INTERACTIONS AMONG HYPOTHALAMIC NEURONS

在激素分泌增加的情况下(例如，在 生殖功能)，下丘脑的神经分泌神经元 室旁核(PVN)形成特征性模式 电活动和神经激素释放。这些模式 激活也是由固有的电特性决定的 如激素分泌细胞的突触组织。本地 突触电路是产生图案化电流的关键 活性，但对局部突触调节知之甚少 神经分泌神经元。这项研究的长期目标是 从生理学和解剖学的角度描述局部突触 室旁核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和 下丘脑室旁核神经元的激素/突触输出。这样做的具体目的是 建议1)确定药理学特征并绘制地形图 从室旁核外的细胞向室旁核神经元的局部突触输入，2)到 确定PVN大细胞和小细胞神经元是否 突触偶联和调节这些的递质或激素 相互作用，以及3)确定PVN的解剖学细胞群 它们接受局部突触输入。在这个过程中 实验中，我们将确定局部突触输入对 已鉴定的PVN细胞的电活动。实验将是 在大鼠下丘脑脑片上使用细胞内、全细胞 PVN细胞的膜片钳和细胞外记录。单元格将是 根据其特征暂时识别为巨细胞或细小细胞 细胞内的电特性。谷氨酸微应用 将被用来有选择地刺激局部神经元以用于地形 包含提供以下功能的细胞的PVN内和外区域的映射 对记录的下丘脑室旁核神经元的抑制性和/或兴奋性突触输入。 PVN细胞与局灶性突触偶联的确凿证据 中间神经元(PVN和非PVN)将通过配对完成 动作电位和突触的记录及其相互关系 活动。将应用特定的拮抗剂来确定 介导这些局部突触的递质和递质受体 互动。激活局部突触传入对大鼠脑电活动的影响 下丘脑室旁核细胞的图案化活动(例如，加压素的时相激发 细胞)将被分析。所有细胞内/膜片钳记录的细胞 将被细胞内标记并通过免疫组织化学鉴定 针对一般神经内科药物的抗体(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。这些组合的电生理- 解剖学研究将阐明局部突触组织。 下丘脑室旁核，并将提供有关生理数据的调节 通过局部突触输入输出的室旁核细胞。

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.