SYNAPTIC PLASTICITY OF HYPOTHALAMIC NEURONS--ESTROGENS

描述：这些实验的长期目标是探索 15β-雌二醇对突触传递的双相效应 对促性腺激素释放激素的抑制和兴奋 (GnRH)神经元。我们的假设是长时间暴露在排卵前 雌激素水平增强兴奋性突触输入并减弱抑制作用 突触传入促性腺激素释放激素神经元，最终促进爆裂 活性和多肽释放。第一批实验将测试 假设雌激素会减少抑制性输入并增加 至少24小时后对GnRH神经元的兴奋性输入。 将从卵巢切除，雌激素和油处理的雌性在 治疗后1、24、36、40h。抑制性神经递质激动剂 (和拮抗剂)对Mu-阿片和GABAB受体的选择性将进行测试 关于POA神经元及其激活的潜在电导 用尖锐的电极记录来表征。兴奋性神经递质 选择性α1去甲肾上腺素能和谷氨酸的激动剂(和拮抗剂) 将对受体及其激活的潜在电导进行测试 以POA(GnRH)神经元为特征。局灶性电刺激 进入POA的传入通路将被用来识别抑制性和 用全细胞膜片记录兴奋性突触电流。第二 实验将检验这样一种假设，即排卵前的E2水平将 增加潜在的相位爆发活动的本征电导 促性腺激素释放激素神经元。组织将由卵巢切除，雌激素和 用油后42h处死雌性大鼠。钙离子的表达 T电流和小电导、钙依赖的K+(SK)电流将 用单电极电压钳和原位杂交法进行测量。 此外，超极化激活的表达， 非选择性阳离子电流(Ih)将用单电极测量 电压钳位。最后，将对注射了生物细胞素的神经元进行分析 组织化学技术结合共聚焦显微镜阐明 注射生物细胞素神经元的递质表型及其解剖 与其他神经元的相互作用。这些研究的结果将提供 关于雌激素改变心脏功能的机制的重要新信息 下丘脑(GnRH)神经元的反应性，以及雌激素一般如何 修改哺乳动物大脑中的突触可塑性。

DESCRIPTION: The long-term objectives of these experiments are to explore the biphasic effects of 15beta-estradiol (E2) on synaptic transmission that results in both inhibition and excitation of gonadotropin releasing hormone (GnRH) neurons. Our hypothesis is that prolonged exposure to preovulatory levels of E2 enhances excitatory synaptic input and attenuates inhibitory synaptic input onto GnRH neurons, which ultimately facilitates bursting activity and peptide release. The first experiments will test the hypothesis that E2 will decrease the inhibitory input and increase the excitatory input to GnRH neurons after a period of at least 24 h. Tissues will be prepared from ovariectomized, estrogen- and oil-treated females at 1, 24, 36, and 40 h after treatment. Inhibitory neurotransmitter agonists (and antagonists) selective for mu-opioid and GABAB receptors will be tested on POA neurons and the underlying conductances which they activate characterized using sharp electrode recording. Excitatory neurotransmitter agonists (and antagonists) selective for alpha1-noradrenergic and glutamate receptors will be tested and the underlying conductances which they activate characterized in POA (GnRH) neurons. Focal electrical stimulation of afferent pathways into the POA will be done to identify inhibitory and excitatory synaptic currents using whole-cell patch recording. The second experiments will test the hypothesis that preovulatory levels of E2 will increase the intrinsic conductances underlying phasic bursting activity in GnRH neurons. Tissues will be prepared from ovariectomized, estrogen- and oil-treated females at 42 h after treatment. The expression of calcium T-current and the small conductance, calcium-dependent K+ (SK) current will be measured using single-electrode voltage clamp and in situ hybridization. In addition, the expression of the hyperpolarization-activated, non-selective cation current (Ih) will be measured using single-electrode voltage clamp. Lastly, the biocytin-injected neurons will be analyzed using histochemical techniques combined with confocal microscopy to elucidate the transmitter phenotype of the biocytin-injected neurons and their anatomical interaction with other neurons. The results from these studies will provide important new information about the mechanism by which estrogen alters the responsiveness of hypothalamic (GnRH) neurons, and how estrogens in general modify synaptic plasticity in the mammalian brain.