Cytochemical and cell biological study on the mechanism of synthesis and action of neurosteroids in the olfactory bulb.

本研究旨在阐明神经类固醇在大鼠和小鼠嗅球中的合成和作用机制，并了解神经类固醇在该器官中的生理作用。结果如下：1)6种类固醇合成酶(P450scc、3β-HSD、17β-HSD、P450c17、芳香酶、5α-还原酶)和雌激素受体(ER)免疫细胞化学定位于嗅球。2)RT-PCR、Northern-blotting和Western-blotting结果表明，上述酶和ER在嗅球的DNA、mRNA和蛋白水平均有表达。3)嗅球中存在P450scc、17β-HSD和5α-还原酶的活性。4)雌激素可抑制嗅球中P450scc、P450c17、3β-HSD和芳香化酶的表达。5)嗅鞘细胞是嗅球内主要的5α-还原酶免疫阳性细胞。而在嗅球的另一层，5α-还原酶免疫阳性细胞为星形胶质细胞和少突胶质细胞。6)为了比较结果，在小脑和海马区进行了免疫组织化学染色。结果表明，5α-还原酶也存在于这些脑区的星形胶质细胞和少突胶质细胞中。7)雌激素或孕酮处理后，小鼠嗅球中P450c17和芳香化酶的mRNAs减少，而二氢睾酮处理则增加。8)本研究结果表明，性激素合成所需的所有酶都存在于嗅球中，这些酶的表达受性类固醇的调控。

This study aims to clarify the mechanism of synthesis and action of neurosteroid in the rat and mouse olfactory bulbs, and to know the physiological roles of neurosteroids in this organ. The results obtained are as follows :1)Steroid synthesixzing enzymes (P450scc, 3beta-HSD, 17beta-HSD, P450c17, aromatase, 5alpha-reductase) and estrogen receptor (ER) were immunocytochemically localized in the olfactory bulb. The enzymes except 5alpha-reductase and ER were present in neurons but 5alpha-reductase was present in glial cells.2)The results of RT-PCR, Northern-blotting, and Western-blotting showed the presence of the enzymes and ER at the DNA, mRNA and pretein level in the olfactory bulb.3)The enzyme actibvities of P450scc, 17beta-HSD and 5alpha-reductase were demonstrated in the olfactory bulb.4)Whe mice were administered with estradiol, the ecpressions of P450scc, P450c17, 3beta-HSD and aromatase were suppressed in the olfactory bulb. However, the expression of the other enzymes and ER did not change.5)Olfactory ensheathing cells were themain 5alpha-reductase immunopositive cells in the olfactory nerve layer of the olfactory bulb. However, in the other layer of the olfactory bulb, the 5alpha-reductase immunopositive cells were astrocytes and oligodendorcytes.6)In order to compare the results, immunohisitochemistry was achieved in the cerebellum and hippocampus. The results showed that 5alpha-reductase was present in astrocytes and oligodendrocytes in these brain areas, too.7)When mice were treated with estradiol or progesterone, mRNAs of P450c17 and aromatase in the olfactory bulb were decreased, but they were increased by the treatment with dihydorotestosterone.8)The present results showed that all the enzymes required for the sex-steroid synthesis were present in the olfactory bulb, and that the expression of the enzymes was controlled by sex-steroids.