Crispino M, Stone D J, Wei M, Anderson C P, Tocco G, Finch C E, Baudry M
Neuroscience Program, University of Southern California, Los Angeles, California, 90089-2520, USA.
Exp Neurol. 1999 Oct;159(2):574-83. doi: 10.1006/exnr.1999.7186.
Periodic changes in ovarian steroid levels during fertility cycles affect learning both in humans and in rats in parallel with electrophysiological and morphological fluctuations in selective neuronal populations. In particular, during the estrous cycle of the female rat, hippocampal CA1 region undergoes cyclic modifications in synaptic density. To investigate the molecular mechanisms involved in synaptic remodeling during the estrous cycle, we analyzed the expression of three presynaptic markers, synaptotagmin I, synaptotagmin IV, and synaptophysin, in the female adult rat brain by in situ hybridization. Relative abundance in mRNA for these three markers was quantified at four phases of the estrous cycle: diestrus, proestrus (AM and PM), and estrus. mRNA levels for syt1 exhibited cyclic variations in pyramidal neurons of the CA3 region of hippocampus during the estrous cycle, while mRNA levels for syt4 and SYN were relatively invariant in this or other regions of the hippocampus. Because CA3 pyramidal neurons make synaptic contacts in CA1, modulation of syt1 expression in CA3 may participate in the changes in synaptic density observed in CA1 during the estrous cycle. Furthermore, both syt1 and SYN mRNA varied cyclically in layer II, but not in layer III of entorhinal cortex, while syt4 remained unchanged throughout the cycle. These data suggest that regular variations in steroid hormone levels during fertility cycles may alter the properties of several networks involved in information processing and learning and memory through altered levels of presynaptic proteins.
在生育周期中，卵巢甾体激素水平的周期性变化会影响人类和大鼠的学习能力，同时选择性神经元群体也会出现电生理和形态学波动。特别是在雌性大鼠的发情周期中，海马CA1区的突触密度会发生周期性变化。为了研究发情周期中突触重塑所涉及的分子机制，我们通过原位杂交分析了成年雌性大鼠脑中三种突触前标志物（突触结合蛋白I、突触结合蛋白IV和突触素）的表达。在发情周期的四个阶段（间情期、动情前期上午和下午、动情期）对这三种标志物的mRNA相对丰度进行了定量。在发情周期中，海马CA3区锥体细胞中syt1的mRNA水平呈现周期性变化，而syt4和SYN在海马的该区域或其他区域的mRNA水平相对不变。由于CA3锥体细胞与CA1区形成突触联系，因此CA3区syt1表达的调节可能参与了发情周期中CA1区观察到的突触密度变化。此外，syt1和SYN的mRNA在内嗅皮层II层呈周期性变化，但在III层则没有，而syt4在整个周期中保持不变。这些数据表明，生育周期中甾体激素水平的规律性变化可能通过改变突触前蛋白水平来改变参与信息处理以及学习和记忆的多个神经网络的特性。
