Brinton R D
Department of Molecular Pharmacology and Toxicology, University of Southern California Pharmaceutical Sciences Center, Los Angeles 90033.
J Neurosci. 1994 May;14(5 Pt 1):2763-74. doi: 10.1523/JNEUROSCI.14-05-02763.1994.
The neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha, 5 alpha-THP) acts as a potent allosteric modulator and a direct activator of the GABA-chloride channel complex. This neurosteroid has also been found to protect against seizures that arise from blockade of the GABA-chloride channel complex. Because 3 alpha,5 alpha-THP protects against excitotoxin-induced seizure activity and because seizure activity has been found to be associated with aberrant hippocampal nerve cell growth, the rapid effect of the neurosteroid 3 alpha,5 alpha-THP upon nerve cell growth was investigated using videomicroscopy of hippocampal neurons in culture. Within 40 min of exposure 3 alpha,5 alpha-THP induced a significant decrease in the area and length of neurites. A concomitant decrement in the number and length of filopodia decorating neuritic extensions also occurred within the 40 min of 3 alpha,5 alpha-THP exposure. Both rapid and slow retrograde movement of intracellular organelles was observed in 3 alpha,5 alpha-THP-treated neurons. 3 alpha,5 alpha-THP-induced regression of neuritic extensions occurred only in nerve cells that had not yet established contact with other nerve or glial cells in culture. Established structural connections between neurons or glia did not erode during 3 alpha,5 alpha-THP exposure. Neither the inactive stereoisomer 3 beta-hydroxy-5 beta-pregnan-20-one nor progesterone had a significant effect upon any of the morphological parameters assessed. In approximately 25% of the cells in which 3 alpha,5 alpha-THP had induced regression, subsequent exposure to 17 beta-estradiol induced profuse filopodial growth within 60 sec of exposure. In cultures similar in age to those used in the morphological studies, 3 alpha,5 alpha-THP induced a significant increase in 36Cl- uptake within 10 sec. The magnitude of 36Cl- uptake was comparable to that induced by exposure to 100 microM GABA. In older, more mature cultures in which the nerve cells had established structural connections, 3 alpha,5 alpha-THP protected cells from picrotoxin-induced nerve cell death. These results demonstrate that 3 alpha,5 alpha-THP can induce regression of neuronal morphology within a relatively rapid time frame. 3 alpha,5 alpha-THP induction of 36Cl- uptake within 10 sec suggests that activation of neurosteroid-regulated chloride channels is an initial step in the biochemical mechanism underlying the retraction induced by this progesterone metabolite steroid. In select instances, 17 beta-estradiol induced an extremely rapid reversal of the filopodial regression produced by 3 alpha,5 alpha-THP.(ABSTRACT TRUNCATED AT 400 WORDS)
神经甾体3α-羟基-5α-孕烷-20-酮（3α，5α-四氢孕酮）作为一种强效变构调节剂和GABA-氯离子通道复合物的直接激活剂。还发现这种神经甾体可预防因GABA-氯离子通道复合物阻断而引发的癫痫发作。由于3α，5α-四氢孕酮可预防兴奋性毒素诱导的癫痫活动，且已发现癫痫活动与海马神经细胞异常生长有关，因此利用培养的海马神经元视频显微镜技术研究了神经甾体3α，5α-四氢孕酮对神经细胞生长的快速作用。在暴露于3α，5α-四氢孕酮40分钟内，其可使神经突的面积和长度显著减小。在暴露于3α，5α-四氢孕酮的40分钟内，装饰神经突延伸的丝状伪足的数量和长度也随之减少。在3α，5α-四氢孕酮处理的神经元中观察到细胞内细胞器的快速和缓慢逆行运动。3α，5α-四氢孕酮诱导的神经突延伸消退仅发生在培养中尚未与其他神经或神经胶质细胞建立联系的神经细胞中。在3α，5α-四氢孕酮暴露期间，神经元或神经胶质之间已建立的结构连接并未受到破坏。非活性立体异构体3β-羟基-5β-孕烷-20-酮和孕酮对所评估的任何形态学参数均无显著影响。在约25%的3α，5α-四氢孕酮诱导消退的细胞中，随后暴露于17β-雌二醇可在暴露后60秒内诱导大量丝状伪足生长。在与形态学研究中所用培养物年龄相似的培养物中，3α，5α-四氢孕酮可在10秒内使36Cl摄取显著增加。36Cl摄取的幅度与暴露于100μM GABA所诱导的幅度相当。在神经细胞已建立结构连接的更成熟的老龄培养物中，3α，5α-四氢孕酮可保护细胞免受印防己毒素诱导的神经细胞死亡。这些结果表明，3α，5α-四氢孕酮可在相对较短的时间内诱导神经元形态消退。3α，5α-四氢孕酮在10秒内诱导36Cl摄取表明，神经甾体调节的氯离子通道激活是这种孕酮代谢物甾体诱导回缩的生化机制的初始步骤。在某些情况下，17β-雌二醇可极其迅速地逆转3α，5α-四氢孕酮引起的丝状伪足消退。（摘要截选至400字）
