Mode of steroid action involving in the behavioral regulation

鸟类的生殖行为受雄激素的调节，为了鉴定参与调节鸟类类固醇激素依赖性行为过程的神经肽，我们分离了三种阿片肽，即Met-和Leu-脑啡肽和Met-脑啡肽-Arg-这是第一次直接证明阿片肽在鸟类脑中的存在。所有三种阿片肽都抑制了视前区和下丘脑区的神经元，已知它们参与几种生殖行为的调节。这种作用被纳洛酮完全阻断，阿片受体拮抗剂。阿片肽可能通过引起神经元活动抑制的机制来调节某些生殖行为。众所周知，脑是外周提供的类固醇激素的靶部位。为了进一步了解脑内参与甾体烯醇酮合成的细胞的定位，本研究用抗细胞色素P450的抗体对脑内参与甾体烯醇酮合成的细胞进行了免疫组织化学研究。结果表明，脑内的甾体烯醇酮主要由胆固醇合成。脑内甾体烯醇酮的积累可能不依赖于外周内分泌腺系统<scc>。在几个端脑，P450 SCC抗体的Western免疫印迹分析证实了P450 SCC的存在，P450 SCC的免疫反应主要发生在小脑分子层的浦肯野细胞胞体和树突中。使用神经胶质细胞的特异性标记蛋白的免疫组织化学显示，神经元和神经胶质细胞都具有P450 SCC-1。就像鸟类大脑中的物质一样

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.