Mode of steroid action involving in the behavioral regulation

鸟类的繁殖行为受雄激素的调节。为了确定与调节鸟类类固醇激素依赖的行为过程有关的神经肽。我们分离了三个阿片肽，即Met-和Leu-Enkephalins和Met-Enkephalin-Arg-Phe。这是首次直接证明阿片肽在鸟类大脑中的存在。这三个阿片肽都抑制了已知参与调节几种生殖行为的视前和下丘脑区域神经元亚群的自发放电活动。这种作用被纳洛酮完全阻断。阿片受体拮抗剂。阿片肽可能通过刺激抑制神经元活动的机制来调节某些生殖行为。众所周知，大脑是由外周类固醇生成腺供应的类固醇激素的靶点。然而，目前的生化实验表明，鸟类的大脑由胆固醇产生孕烯醇酮。孕烯醇酮在脑中的大部分积累可能不依赖于外周内分泌腺系统。为了了解参与孕烯醇酮合成的细胞的定位，用细胞色素P450和lt抗体进行了免疫组织化学研究。在禽脑中进一步发现了鳞状细胞癌。在端脑、间脑和中脑的几个区域都检测到了免疫反应阳性的细胞体。浦肯野细胞的胞体和延伸到小脑分子层的树突中有强烈的免疫反应。用P450scc抗体进行免疫印迹分析证实，这些脑区存在P450scc样物质。用胶质细胞的特异性标记蛋白进行免疫组织化学研究表明，神经元和神经胶质细胞在禽脑中都具有P450scc样物质。

Avian reproductive behaviors are under androgen regulation.To identify the neuropetides that are implicated in the regulation of steroid hormone dependent behavioral processes in birds.We have isolated three opioid peptides, i.e.Met-and Leu-enkephalins and Met-enkephalin-Arg-Phe.This is the first direct demonstration of the presence of opioid peptides in the avian brain.All of the three opioid peptides inhibited the spontaneous firing activities of subsets of neurons in the preoptic and hypothalamic areas that are known to be involved in the regulation of several reproductive behavior.Such an effect was completely blocked by naloxone, an opioid receptor antagonist.It may be possible that opioid peptides regulate some reproductive behavior through the mechanism that provokes the inhibition of neuronal activities.It is well known that the brain is a target site of steroid hormones supplied by peripheral steroidogenic glands.However, present biochemical experiments demonstrated that the avian brain produces pregnenolone from cholesterol.Most accumulation of pregnenolone in the brain may be independent of the peripheral endocrine gland system.To understand the localization of cells involving with pregnenolone synthesis, the immunohistochemical study with the antibody against cytochrome P450_<scc> was further undertaken in the avian brain.Clusters of immunoreactive cell bodies were detected in several telencephalic, diencephalic and mesencephalic regions.An intense immunoreaction was detected in somata of Purkinje cells and in the dendrites extending through the cerebellar molecular layr.Western immunoblot analysis with the P450scc antibody confirmed the presence of a P450scc-like substance in these brain regions.Immunohistochemistry using a specific marker protein of glial cells revealed that both neuronal and glial cells possess a P450scc-like substance in the avian brain.