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和Gt_2，但不能诱导IP激动剂U-46619和TP激动剂卡巴环素引起星形胶质细胞[Ca~(2+)]升高。星形胶质细胞的RT-PCR分析显示所有已知的8个PG受体mRNAs。为了阐明前列腺素(PG)调节神经元和内分泌细胞的确切细胞和分子机制，我们检测了膜电位、膜电流、胞浆钙浓度([Ca^&lt；2&gt；])和几种类型细胞的mRNAs。1)视上核(SON)神经元PGE_2和PGF_lt；2a和gt；2a&gt；引起动作电位放电、阳离子电流、催产素和血管紧张素释放和[Ca^&lt；这些作用可被选择性的EP_4激动剂ONO-AE1-329和FP激动剂氟前列烯醇所模拟，而EP_1激动剂OQ-DI-004、EP_2激动剂ONO-AE1-257和EP_3激动剂ONO-AE-248几乎没有作用。前列腺素E_2…更多而不是PGF_2a&gt；可在不影响幅度的情况下降低自发抑制突触后电流(IPSCs)的频率。EP3激动剂与之相似，而其他三种选择性EP激动剂的作用不明显。这些结果表明，在SON神经元突触前和突触后部位均存在PG受体：突触后EP_4和FP受体与非选择性阳离子通道偶联，激活非选择性阳离子通道，导致膜去极化和钙离子通过电压门控性钙通道进入；突触前EP_3受体抑制GABA释放，使SON神经元失去抑制作用。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神经元的调节中起重要作用。2)肾上腺嗜铬细胞PGE_2和ONO-DI-004诱导的Ca？？释放和Ca？进入培养的牛肾上腺嗜铬细胞。RT-PCR分析表明，大鼠肾上腺髓质表达EP_1、EP_3、EP_4受体mRNAs，提示EP1受体在嗜铬细胞中的作用。3)PGE_2和ONO-AE-248中的黑素营养细胞引起[Ca^&lt；2&gt；]降低。PGE_2抑制电压门控性钙通道电流，但对内向整流钾电流影响不大。4)背根神经节(DRG)神经元PGE_2、ONO-AE1-257和ONO-AE1-328诱导辣椒素敏感的小鼠背根神经节神经元[Ca^&lt；2&gt；]升高，表明EP_2和EP_4受体参与了痛觉。6)小鼠侧脑室注射四种选择性EP2受体激动剂中的任何一种对小鼠的饮酒和其他行为几乎没有影响。较少

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