Wingfield John C, Wacker Douglas W, Bentley George E, Tsutsui Kazuyoshi
Department of Neurobiology Physiology and Behavior, University of California, Davis, Davis, CA, United States.
Division of Biological Sciences, School of STEM, University of Washington Bothell, Bothell, WA, United States.
Front Endocrinol (Lausanne). 2018 Jun 18;9:270. doi: 10.3389/fendo.2018.00270. eCollection 2018.
Biological steroids were traditionally thought to be synthesized exclusively by the adrenal glands and gonads. Recent decades have seen the discovery of neurosteroid production that acts locally within the central nervous system to affect physiology and behavior. These actions include, for example, regulation of aggressive behavior, such as territoriality, and locomotor movement associated with migration. Important questions then arose as to how and why neurosteroid production evolved and why similar steroids of peripheral origin do not always fulfill these central roles? Investigations of free-living vertebrates suggest that synthesis and action of bioactive steroids within the brain may have evolved to regulate expression of specific behavior in different life history stages. Synthesis and secretion of these hormones from peripheral glands is broadcast throughout the organism the blood stream. While widespread, general actions of steroids released into the blood might be relevant for regulation of morphological, physiological, and behavioral traits in one life history stage, such hormonal release may not be appropriate in other stages. Specific and localized production of bioactive steroids in the brain, but not released into the periphery, could be a way to avoid such conflicts. Two examples are highlighted. First, we compare the control of territorial aggression of songbirds in the breeding season under the influence of gonadal steroids with autumnal (non-breeding) territoriality regulated by sex steroid production in the brain either from circulating precursors such as dehydroepiandrosterone or local central production of sex steroids from cholesterol. Second, we outline the production of 7α-hydroxypregnenolone within the brain that appears to affect locomotor behavior in several contexts. Local production of these steroids in the brain may provide specific regulation of behavioral traits throughout the year and independently of life history stage.
传统上认为生物类固醇仅由肾上腺和性腺合成。近几十年来，人们发现了神经类固醇的产生，其在中枢神经系统内局部起作用，影响生理和行为。这些作用包括，例如，对攻击行为的调节，如领地行为，以及与迁徙相关的运动活动。于是就出现了一些重要问题，即神经类固醇的产生是如何以及为何进化的，以及为什么外周来源的类似类固醇并不总是发挥这些中枢作用？对自由生活的脊椎动物的研究表明，大脑中生物活性类固醇的合成和作用可能已经进化，以调节不同生命史阶段特定行为的表达。这些激素从外周腺体的合成和分泌通过血液循环遍布整个生物体。虽然释放到血液中的类固醇的广泛、一般作用可能与一个生命史阶段的形态、生理和行为特征的调节有关，但这种激素释放可能在其他阶段并不合适。大脑中生物活性类固醇的特异性和局部产生，但不释放到外周，可能是避免此类冲突的一种方式。文中突出了两个例子。首先，我们比较了在繁殖季节性腺类固醇影响下鸣禽的领地攻击行为的控制，与秋季（非繁殖期）由大脑中由循环前体如脱氢表雄酮产生的性类固醇或由胆固醇局部中枢产生的性类固醇调节的领地行为。其次，我们概述了大脑中7α-羟基孕烯醇酮的产生，它似乎在多种情况下影响运动行为。大脑中这些类固醇的局部产生可能全年独立于生命史阶段对行为特征进行特异性调节。
