Morissette M, Garcia-Segura L M, Bélanger A, Di Paolo T
School of Pharmacy, Laval University, Ste-Foy, Québec, Canada.
Neuroscience. 1992 Aug;49(4):893-902. doi: 10.1016/0306-4522(92)90365-9.
It is well documented that sex steroids affect striatal dopamine systems. However, the mechanism(s) of these hormonal effects in the striatum is still not well understood. We now report that gonadal steroid hormones during the estrous cycle affect the morphology and steroid hormone content of the rat striatum. Rats displaying at least two consecutive estrous cycles were included in this study as well as a group of female rats ovariectomized two weeks before being killed. The striatum was dissected from one half of each brain and used for morphological studies. From the other half of each brain, the striatum was dissected and steroid hormone concentrations in striatum and the remainder of the brain were determined. Tissues and serum concentrations of 17 beta-estradiol, progesterone and prolactin were measured by specific radioimmunoassays. Serum 17 beta-estradiol and prolactin concentrations peaked in proestrus, while progesterone was high in diestrus and proestrus. 17 beta-Estradiol levels were higher in the striatum than in the rest of the brain; both were also shown to fluctuate during the estrous cycle and with a pattern similar to that observed in serum. Progesterone serum levels showed a similar pattern of changes during the estrous cycle to progesterone concentrations in the striatum and the rest of the brain. The ultrastructure of the striatal dendritic membranes was studied by freeze-fracture. A significant difference in the content of intramembranous particles in dendritic shafts, which are mainly contacted by dopaminergic synapses, was found during the estrous cycle. The numerical density of large (greater than 10 nm) intramembranous particles was increased in diestrus I and II and in the afternoon of proestrus compared to estrus, the morning of proestrus and ovariectomized rats. In contrast, the numerical density of small (less than 10 nm) intramembranous particles was decreased in cycling animals compared to ovariectomized rats and fell in the afternoon of proestrus and then progressively increased in the following days to peak in the morning of proestrus. A negative correlation between steroid concentrations and small intramembranous particle density was observed, while the correlation was positive for large particles. No changes were observed in the membranes of dendritic spines, the main postsynaptic target for cortical afferents. In summary, this is the first report that concentrations of 17 beta-estradiol and progesterone in the striatum fluctuate during the estrous cycle. This is associated with estrous cycle-dependent changes of intramembranous particle density of striatal dendritic membranes. Our data therefore indicate that the striatum is a brain region hormonally modulated under physiological conditions.
有充分的文献记载表明，性类固醇会影响纹状体多巴胺系统。然而，这些激素在纹状体中的作用机制仍未得到充分理解。我们现在报告，发情周期中的性腺类固醇激素会影响大鼠纹状体的形态和类固醇激素含量。本研究纳入了至少经历两个连续发情周期的大鼠，以及一组在处死前两周进行卵巢切除的雌性大鼠。从每只大脑的一半中分离出纹状体用于形态学研究。从每只大脑的另一半中分离出纹状体，并测定纹状体和大脑其余部分的类固醇激素浓度。通过特异性放射免疫测定法测量组织和血清中17β - 雌二醇、孕酮和催乳素的浓度。血清17β - 雌二醇和催乳素浓度在动情前期达到峰值，而孕酮在动情后期和动情前期含量较高。纹状体中的17β - 雌二醇水平高于大脑其余部分；两者在发情周期中也呈现波动，且模式与血清中观察到的相似。血清孕酮水平在发情周期中的变化模式与纹状体及大脑其余部分的孕酮浓度相似。通过冷冻蚀刻研究纹状体树突状膜的超微结构。发现在发情周期中，主要与多巴胺能突触接触的树突干中膜内颗粒含量存在显著差异。与发情期、动情前期早晨及卵巢切除的大鼠相比，在动情后期I和II以及动情前期下午，大（大于10 nm）膜内颗粒的数量密度增加。相反，与卵巢切除的大鼠相比，处于发情周期的动物中小（小于10 nm）膜内颗粒的数量密度降低，且在动情前期下午下降，随后在接下来的几天中逐渐增加，在动情前期早晨达到峰值。观察到类固醇浓度与小膜内颗粒密度之间呈负相关，而与大颗粒呈正相关。在树突棘膜（皮质传入的主要突触后靶点）中未观察到变化。总之，这是首次报道纹状体中17β - 雌二醇和孕酮浓度在发情周期中波动。这与纹状体树突状膜膜内颗粒密度的发情周期依赖性变化相关。因此，我们的数据表明纹状体是在生理条件下受激素调节的脑区。
