Analysis of prostaglandig-mediated regulatory mechanisms in the neuronal and endocrine systems

5)星形胶质细胞PGE_2， PGD_2, PGF_<2a>，但IPagonist U-46619和TP激动剂carbacyclin均未诱导[Ca?？]，在培养大鼠星形胶质细胞中。星形胶质细胞的RT-PCR分析显示了所有已知的8种PG受体mrna。这些多种PG受体可能通过PG参与中枢神经系统的信号转导。为了阐明前列腺素（PG）介导的神经元和内分泌细胞调节的精确细胞和分子机制，我们研究了几种类型细胞的膜电位、膜电流、胞质Ca^<2+>浓度（[Ca^<2+>]）和mrna。1)视上核（SON）神经元PGE_2和PGF_<2a>引起动作电位放电、阳离子电流、垂体后叶催产素和加压素释放及Ca^<2+>升高。EP_4选择性激动剂ONO-AE1-329和FP激动剂氟前列腺醇均能模拟上述作用，而EP_1激动剂ONQ-DI-004、EP_2激动剂ONO-AE1-257和EP_3激动剂ONO-AE-248的作用不大。PGF_<2a>对自发性抑制性突触后电流（IPSCs）的频率有明显的抑制作用，但对IPSCs的振幅没有影响。EP_3激动剂具有类似的作用，但其他3种选择性EP_3激动剂作用不大。这些结果表明PG受体同时存在于SON神经元的突触前和突触后：突触后EP_4和FP受体偶联于非选择性阳离子通道，其激活导致膜去极化和Ca^<2+>通道通过电压门控Ca^<2+>通道进入；GABA神经元突触前EP_3受体抑制GABA释放，导致SON神经元去抑制。这些由突触前和突触后PG受体介导的多种兴奋机制可能在PG对SON神经元的调控中发挥重要作用。2)肾上腺染色质细胞PGE_2和ONO-DI-004诱导Ca?？释放和Ca?？进入培养的牛肾上腺嗜铬细胞。RT-PCR分析显示，大鼠肾上腺髓质表达EP_1、EP_3、EP_4受体mrna，提示ep1受体在嗜铬细胞中发挥作用。3)垂体部间质PGE_2和ONO-AE-248的黑色素瘤导致[Ca^<2+>]降低。PGE_2抑制电压门控Ca^<2+>通道电流，但对内整流K^+电流影响不大。EP_3受体mRNA在pars中间组织中表达，表明EP_3受体与电压门控Ca^<2+>通道选择性偶联。4)背根神经节（DRG）神经元PGE_2、ONO-AE1-257和ONO-AE1-328诱导辣椒素敏感小鼠DRG神经元[Ca^<2+>]升高，表明EP_2和EP_4受体参与了伤害感受。6)在小鼠的全动物实验中，在脑室内注射四种选择性EPagonists中的任何一种对饮酒和其他行为的影响都很小。少

5) Astrocytes PGE_2, PGD_2, PGF_<2a>, but neither IPagonist U-46619 nor TP agonist carbacyclin, induced a rise in [Ca??], in cultured rat astrocytes. RT-PCR analysis of astrocytes revealed all known 8 PG receptor mRNAs. These multiple PG receptors may be involved in signal transduction via PGs in the CNS.To elicidate the precise cellular and molecular mechanisms involved in the prostaglandin (PG)-mediated regulation of neuronal and endocrine cells, we have examined membrane potentials, membrane currents, cytosolic Ca^<2+> concentration ([Ca^<2+>]) and mRNAs in several types of cells.1) Supraoptic nucleus (SON) neurons PGE_2 and PGF_<2a> caused an increase in the action potential discharge, cationic currents, somatodendritic release of oxytocin and vasopressin and in [Ca^<2+>]. These effects were mimicked by the selective EP_4 agonist ONO-AE1-329 and the FP agonist fluprostenol, while EP_1 agonist ONQ-DI-004, EP_2 agonist ONO-AE1-257 and EP_3 agonist ONO-AE-248 had little effect. PGE_2 … More but not PGF_<2a> reduced the frequency of spontaneous inhibitory postsynaptic currents (IPSCs) without affecting the amplitude. This was mimicked by the EP_3 agonist but other three selective EPagonist had little effect. These results indicate that PG receptors are present both at the pre- and post-synaptic sites of SON neurons : postsynaptic EP_4 and FP receptors are coupled to non-selective cation channels, activation of which results in membrane depolarization and Ca^<2+> entry through voltage-gated Ca^<2+> channels ; and presynaptic EP_3 receptors in GABA neurons suppress GABA release, which results in disinhibition of SON neurons. These multiple excitatory mechanisms mediated by pre- and postsynaptic PG receptors may play important roles in the regulation of SON neurons by PGs.2) Adrenal chromaffin cells PGE_2 and ONO-DI-004 induced Ca?? release and Ca?? entry in cultured bovine adrenal chromaffin cells. RT-PCR analysis revealed that the adrenal medulla of rats express EP_1, EP_3, EP_4 receptor mRNAs, suggesting a role of EP1receptors in the chromaffin cells.3) Melanotrophs of the pituitary pars intermedia PGE_2, and ONO-AE-248 caused a reduction in [Ca^<2+>]. PGE_2 suppressed voltage-gated Ca^<2+> channel currents, but had little effect on inwardly rectifying K^+ currents. EP_3 receptor mRNA was detected in the pars intermedia tissue, suggesting EP_3 receptors are selectively coupled with voltage-gated Ca^<2+> channels.4) Dorsal root ganglion (DRG) neurons PGE_2, ONO-AE1-257 and ONO-AE1-328 induced a rise in [Ca^<2+>], in capsaicin-sensitive mouse DRG neurons, indicating EP_2 and EP_4 receptors are involved in nociception.6) Whole-animal experiments with mice Intracerebroventricular injection of any of the four selective EPagonists had little effect on drinking and other behaviors. Less