Department of Anesthesiology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan.
Synapse. 2019 Mar;73(3):e22076. doi: 10.1002/syn.22076. Epub 2018 Nov 3.
Allopregnanolone, an active metabolite of progesterone, has been reported to exhibit neuroprotective activity in several preclinical models. Considering that the excitotoxicity caused by excessive glutamate is implicated in many brain disorders, the effect of allopregnanolone on glutamate release in rat cerebrocortical nerve terminals and possible underlying mechanism were investigated. We observed that allopregnanolone inhibited 4-aminopyridine (4-AP)-evoked glutamate release, and this inhibition was prevented by chelating the extracellular Ca ions and the vesicular transporter inhibitor. Allopregnanolone reduced the elevation of 4-AP-evoked intrasynaptosomal Ca levels, but did not affect the synaptosomal membrane potential. In the presence of N-, P/Q-, and R-type channel blockers, allopregnanolone-mediated inhibition of 4-AP-evoked glutamate release was markedly reduced; however, the intracellular Ca -release inhibitors did not affect the allopregnanolone effect. Furthermore, allopregnanolone-mediated inhibition of 4-AP-evoked glutamate release was completely abolished in the synaptosomes pretreated with inhibitors of Ca /calmodulin, adenylate cyclase, and protein kinase A (PKA), namely calmidazolium, MDL12330A, and H89, respectively. Additionally, the allopregnanolone effect on evoked glutamate release was antagonized by the GABA receptor antagonist SR95531. Our data are the first to suggest that allopregnanolone reduce the Ca influx through N-, P/Q-, and R-type Ca channels, through the activation of GABA receptors present on cerebrocortical nerve terminals, subsequently suppressing the Ca -calmodulin/PKA cascade and decreasing 4-AP-evoked glutamate release.
别孕烯醇酮，孕酮的一种活性代谢物，已被报道在几种临床前模型中具有神经保护活性。由于过量谷氨酸引起的兴奋性毒性与许多脑部疾病有关，因此研究了别孕烯醇酮对大鼠大脑皮质神经末梢谷氨酸释放的影响及其潜在机制。我们观察到别孕烯醇酮抑制 4-氨基吡啶（4-AP）诱导的谷氨酸释放，这种抑制作用可通过螯合细胞外 Ca 离子和囊泡转运抑制剂来预防。别孕烯醇酮降低了 4-AP 诱导的突触体内 Ca 水平的升高，但不影响突触体膜电位。在存在 N、P/Q 和 R 型通道阻滞剂的情况下，别孕烯醇酮介导的 4-AP 诱导的谷氨酸释放抑制明显减少；然而，细胞内 Ca 释放抑制剂不影响别孕烯醇酮的作用。此外，在经 Ca/钙调蛋白、腺苷酸环化酶和蛋白激酶 A（PKA）抑制剂预处理的突触体中，别孕烯醇酮介导的 4-AP 诱导的谷氨酸释放抑制完全被消除，这些抑制剂分别为氯氮卓、MDL12330A 和 H89。此外，GABA 受体拮抗剂 SR95531 拮抗了别孕烯醇酮对诱发谷氨酸释放的作用。我们的数据首次表明，别孕烯醇酮通过激活存在于大脑皮质神经末梢上的 GABA 受体，减少 N、P/Q 和 R 型 Ca 通道的 Ca 内流，随后抑制 Ca-钙调蛋白/PKA 级联反应，降低 4-AP 诱导的谷氨酸释放。
