Porkka-Heiskanen T, Urban J H, Turek F W, Levine J E
Department of Physiology, University of Helsinki, Finland.
J Neurosci. 1994 Sep;14(9):5548-58. doi: 10.1523/JNEUROSCI.14-09-05548.1994.
Gene expression in luteinizing hormone-releasing hormone (LHRH) neurons was analyzed during the periovulatory period to (1) characterize temporal patterns of LHRH gene expression and their relationship(s) to gonadotropin surges, and (2) determine if any such changes are uniform or dissimilar at different rostrocaudal levels of the basal forebrain. The number of neurons expressing mRNA for the decapeptide, and the relative degree of expression per cell were analyzed using in situ hybridization and quantitative image analysis. Rats were killed at 1800 hr on metestrus (Met), 0800 hr, 1200 hr, 1800 hr, and 2200 hr on proestrus (Pro), or 0200 hr, 0800 hr, and 1800 hr on estrus (E; n = 5-6 rats/group). All sections were processed for LHRH mRNA in a single in situ hybridization assay. Sections were atlas matched and divided into four rostrocaudal groups for analysis: vertical limb of the diagonal band of Broca (DBB), rostral preoptic area/organum vasculosum of the lamina terminalis (rPOA/OVLT), medial preoptic area (mPOA), and suprachiasmatic/anterior hypothalamic area (SCN/AHA). Plasma LH and FSH levels from all animals were analyzed by RIA. The labeling intensity per cell was similar among all time points at all four rostrocaudal levels. The number of cells expressing LHRH mRNA, however, varied as a function of time of death during the estrous cycle, and this temporal pattern varied among the four anatomical regions. At the level of the mPOA, the number of cells was highest at 1200 hr on Pro, and then declined and remained low throughout the morning of E. At the level of the rPOA/OVLT, the greatest number of LHRH neurons was noted later in Pro, at 1800 hr, dropping rapidly to lowest numbers at 2200 hr. No significant changes in LHRH cell number occurred at the DBB or SCN/AHA levels. At all anatomical levels, the secondary surge of FSH was unaccompanied by any change in the number of neurons expressing LHRH mRNA. These data demonstrate that (1) the number of detectable LHRH mRNA-expressing cells fluctuates during the periovulatory period and (2) peak numbers of LHRH-expressing cells are attained in the mPOA before the onset of the LH surge and before peak LHRH cell numbers are seen at more rostral levels. A model is proposed in which gene expression in this subpopulation of LHRH neurons may be activated by preovulatory estrogen secretion and acutely reduced following the proestrous surge of progesterone.
在排卵期前后分析促黄体生成素释放激素（LHRH）神经元中的基因表达，目的是：（1）描绘LHRH基因表达的时间模式及其与促性腺激素激增的关系，以及（2）确定在基底前脑不同的前后水平上，此类变化是一致的还是不同的。使用原位杂交和定量图像分析，分析表达十肽mRNA的神经元数量以及每个细胞的相对表达程度。在动情后期（Met）的18:00、动情前期（Pro）的08:00、12:00、18:00和22:00，或发情期（E）的02:00、08:00和18:00处死大鼠（每组n = 5 - 6只大鼠）。所有切片在一次原位杂交实验中进行LHRH mRNA处理。将切片与图谱匹配，并分为四个前后组进行分析：布罗卡斜角带垂直支（DBB）、终板前视区/终板血管器（rPOA/OVLT）、视前内侧区（mPOA）和视交叉上核/下丘脑前区（SCN/AHA）。通过放射免疫分析法分析所有动物的血浆LH和FSH水平。在所有四个前后水平的所有时间点，每个细胞的标记强度相似。然而，表达LHRH mRNA的细胞数量在发情周期中随死亡时间而变化，并且这种时间模式在四个解剖区域中有所不同。在mPOA水平，细胞数量在Pro的12:00最高，然后下降，并在E的整个上午保持较低水平。在rPOA/OVLT水平，在Pro后期的18:00观察到最多的LHRH神经元，在22:00迅速降至最低数量。在DBB或SCN/AHA水平，LHRH细胞数量没有显著变化。在所有解剖水平，FSH的第二次激增并未伴随表达LHRH mRNA的神经元数量的任何变化。这些数据表明：（1）在排卵期前后，可检测到的表达LHRH mRNA的细胞数量波动；（2）在LH激增开始之前以及在更靠前的水平出现LHRH细胞数量峰值之前，mPOA中达到表达LHRH细胞的峰值数量。提出了一个模型，其中该亚群LHRH神经元中的基因表达可能由排卵前雌激素分泌激活，并在动情前期孕酮激增后急剧减少。
