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GABA-induced currents and their modulation by neurosteroids in rat GnRH neurons

大鼠 GnRH 神经元中 GABA 诱导的电流及其神经类固醇的调节

基本信息

批准号：
16590180
负责人：
KATO Masakatsu
金额：
$ 2.3万
依托单位：
Nippon Medical School
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

Voltage-gated ionic channel currents and GABAA receptor current in rat GnRH neurons were analyzed. Under deep anesthesia, brains were excised from adult GnRH-EGFP transgenic rats. After dissection, brains were enzymatically dispersed and the neurons were plated on coverslips and cultured overnight. Then the neurons were applied for perforated patch-clamp experiment. GnRH neurons, identified with EGFP-fluorescnce, exhibited the voltage-gated calcium currents, which were composed with L-, N-, P/Q-, R- and T-types. The R-type contributed 30% for total calcium current. L-, N-, P/Q- and T-type contributed 25, 20, 12 and 13%, respectively (Kato et al., 2006). This expression pattern differs from those of neonatal GnRH neurons but is similar to those from pubertal neurons. Therefore, expression pattern of voltage-gated calcium channels in rat GnRH neurons are developmentally regulated and completed around puberty. To study the roles of these calcium channels, we investigated the calcium-activ … More ated potassium currents. Rat GnRH neurons showed two types of calcium activated potassium currents. They were calcium- and voltage-activated potassium current (BK) and calcium-activated slow afterhyperpolarization current. The latter was specifically inhibited by SK channel blocker apamin. This slow afterhyperpolarization current is, therefore, carried through the SK channels. Furthermore, this current contributed for persistent firing evoked by strong depolarization (Kato et al., 2005, Japan Neuroscience Meeting ; Kato et al., 2006). Finally, we analyzed GABA action on rat GnRH neurons by means of calcium imaging method. GABA acted on the GABAA receptor and elevated intracellular calcium concentration in more than 50% of GnRH neurons isolated from adult rats. This GABA-induced response was abolished by the removal of extracellular calcium and by blocking the chloride transporter NKCC1. Therefore, GABA depolarizes rat GnRH neurons by acting GABAA receptor, thereby activating the voltage-gated calcium channels (Tanaka et al. 2006, International Congress of Neuroendocrinology; Watanabe et al., 2006 in preparation). Less

分析了大鼠 GnRH 神经元中的电压门控离子通道电流和 GABAA 受体电流。在深度麻醉下，从成年 GnRH-EGFP 转基因大鼠中切除大脑。解剖后，用酶法分散大脑，并将神经元铺在盖玻片上并培养过夜。然后将神经元用于穿孔膜片钳实验。 EGFP荧光鉴定的GnRH神经元表现出电压门控钙电流，其由L型、N型、P/Q型、R型和T型组成。 R型占总钙电流的30%。 L型、N型、P/Q型和T型分别占25%、20%、12%和13%（Kato等，2006）。这种表达模式与新生儿 GnRH 神经元的表达模式不同，但与青春期神经元的表达模式相似。因此，大鼠 GnRH 神经元中电压门控钙通道的表达模式在青春期左右受到发育调节和完成。为了研究这些钙通道的作用，我们研究了钙激活钾电流。大鼠 GnRH 神经元表现出两种类型的钙激活钾电流。它们是钙和电压激活的钾电流（BK）和钙激活的慢后超极化电流。后者被 SK 通道阻断剂 apamin 特异性抑制。因此，这种缓慢的后超极化电流通过 SK 通道进行。此外，该电流有助于强去极化引起的持续放电（Kato 等人，2005，日本神经科学会议；Kato 等人，2006）。最后，我们通过钙成像方法分析了GABA对大鼠GnRH神经元的作用。 GABA 作用于 GABAA 受体，使成年大鼠分离的超过 50% 的 GnRH 神经元的细胞内钙离子浓度升高。这种 GABA 诱导的反应可通过去除细胞外钙和阻断氯离子转运蛋白 NKCC1 来消除。因此，GABA通过作用GABAA受体使大鼠GnRH神经元去极化，从而激活电压门控钙通道（Tanaka等人，2006年，国际神经内分泌学大会；Watanabe等人，2006年准备中）。较少的