Watson R E, Langub M C, Engle M G, Maley B E
Department of Anatomy and Neurobiology, University of Kentucky, Medical Center, Lexington 40536-0084, USA.
Brain Res. 1995 Aug 21;689(2):254-64. doi: 10.1016/0006-8993(95)00548-5.
The anteroventral periventricular nucleus (AVPv) in the rat preoptic area is a key site underlying control of the steroid dependent preovulatory gonadotropin surge. Estrogen and progesterone receptor-containing neurons in the preoptic/hypothalamic continuum, particularly those in the AVPv, are believed to transduce steroidal signals and, in turn convey this information to the LHRH system, which lacks steroid receptors. In addition to the influence of the gonadal steroids, the precise timing of the preovulatory gonadotropin surge is believed to be regulated by the hypothalamic suprachiasmatic nucleus (SCN). The SCN and peri-SCN neurons send efferent projections rostrally to the anterior preoptic area suggesting that circadian signals are communicated synaptically to steroid-responsive neurons in the AVPv. To test this hypothesis, ultrastructural double label immunocytochemistry was conducted to determine whether SCN efferents contact estrogen receptor-immunoreactive neurons in the AVPv. Brain sections with SCN injections of phaseolus vulgaris leucoagglutinin (PHA-L) were immunostained for estrogen receptors and PHA-L. Light and electron microscopic data show that the anterior preoptic area received robust PHA-L-immunoreactive efferents from SCN neurons and immediately adjacent subparaventricular zone. In particular, the AVPv contained abundant labeled fibers and terminal boutons. Ultrastructurally, SCN- and subparaventricular zone-derived terminals synaptically contacted the perikaryon of many estrogen receptor-immunoreactive neurons in the AVPv. The perikarya of unlabeled neurons were also contacted, but the majority of the labeled contacts were observed upon neuronal processes. These results demonstrate that estrogen responsive AVPv neurons are regulated by SCN efferents. Furthermore, the present data provide strong support to the idea of collective control of pituitary gonadotropin release by steroid sensitive and circadian signal neural pathways.
大鼠视前区的腹侧室周核（AVPv）是类固醇依赖性排卵前促性腺激素激增控制的关键部位。视前区/下丘脑连续区域中含有雌激素和孕激素受体的神经元，尤其是AVPv中的那些神经元，被认为可转导类固醇信号，并将此信息传递给缺乏类固醇受体的促性腺激素释放激素（LHRH）系统。除了性腺类固醇的影响外，排卵前促性腺激素激增的精确时间被认为受下丘脑视交叉上核（SCN）调节。SCN和SCN周围神经元向前发出传出投射至视前区前部，这表明昼夜节律信号通过突触传递给AVPv中的类固醇反应性神经元。为了验证这一假设，进行了超微结构双重标记免疫细胞化学实验，以确定SCN传出纤维是否与AVPv中雌激素受体免疫反应性神经元接触。对注射了菜豆白细胞凝集素（PHA-L）的SCN的脑切片进行雌激素受体和PHA-L免疫染色。光镜和电镜数据显示，视前区前部接收到来自SCN神经元和紧邻的室旁核下区的大量PHA-L免疫反应性传出纤维。特别是，AVPv含有丰富的标记纤维和终末小体。在超微结构上，源自SCN和室旁核下区的终末与AVPv中许多雌激素受体免疫反应性神经元的胞体形成突触联系。未标记神经元的胞体也有接触，但大多数标记接触见于神经元突起。这些结果表明，雌激素反应性AVPv神经元受SCN传出纤维调节。此外，目前的数据为类固醇敏感和昼夜节律信号神经通路对垂体促性腺激素释放的集体控制观点提供了有力支持。
