Kromkhum Pudcharaporn, Nagai Asa, Ichikawa Masumi, Saito Toru R, Yokosuka Makoto
Department of Comparative and Behavioral Medicine Nippon Veterinary and Life Science University 1-7-1 Kyonancho 180-8602 Musashino Tokyo Japan.
Department of Physiology Kasetsart University 109000 Bangkok Thailand.
Reprod Med Biol. 2009 Apr 25;8(2):79-84. doi: 10.1007/s12522-009-0013-1. eCollection 2009 Jun.
Elucidation of the neural mechanism of maternal behaviors is a medically and biologically important research task. The rat is the laboratory animal most extensively analyzed for maternal behaviors. However, the neural mechanism that maintains the motivation of postpartum rats for maternal behaviors has not yet been elucidated. In this study, we aimed to identify brain regions involved in the maintenance of motivation for maternal behaviors by detecting brain regions that exhibit changes in nerve activity when the mother rat is separated from her pups.
Lactating mother rats were separated from their pups on postpartum day 3 and kept away from the pups for a certain period of time, and brain regions that exhibited changes in nerve activity when the rats were separated from their pups and those that exhibited changes in nerve activity when the pups are returned were detected by immunohistochemistry using anti-c-Fos antibody, a marker for increased nerve activity.
Rats that were separated from their pups and with the pups returned later showed increases in the number of c-Fos immunoreactive (c-Fos-IR) cells in the medial preoptic area (MPA), the bed nucleus of the stria terminalis (BST), the caudal portion of posterior hypothalamic area (PH) and the supramamillary nucleus (SUM). In mother rats permanently separated from their pups, only the PH and SUM exhibited an increase in the number of c-Fos-IR cells.
In rats, the SUM is involved in aversive memory and changes in the postpartum anxiety level. The observed increase in the number of c-Fos-IR cells in the SUM of mother rats separated from their pups suggests that the nerve activity change in the SUM, which is involved in aversive memory and anxiety, is involved in the maintenance of maternal behaviors.
阐明母性行为的神经机制是一项具有医学和生物学重要意义的研究任务。大鼠是对母性行为进行最广泛分析的实验动物。然而，产后大鼠维持母性行为动机的神经机制尚未阐明。在本研究中，我们旨在通过检测当母鼠与其幼崽分离时神经活动发生变化的脑区，来确定参与维持母性行为动机的脑区。
在产后第3天将哺乳期母鼠与其幼崽分离，并使其在一段时间内远离幼崽，然后使用抗c-Fos抗体（一种神经活动增加的标志物）通过免疫组织化学方法检测当大鼠与幼崽分离时神经活动发生变化的脑区以及当幼崽返回时神经活动发生变化的脑区。
与幼崽分离后又让幼崽返回的大鼠，视前内侧区（MPA）、终纹床核（BST）、下丘脑后区（PH）尾侧部分和乳头体上核（SUM）中c-Fos免疫反应性（c-Fos-IR）细胞数量增加。在与幼崽永久分离的母鼠中，只有PH和SUM的c-Fos-IR细胞数量增加。
在大鼠中，SUM参与厌恶记忆和产后焦虑水平的变化。与幼崽分离的母鼠SUM中观察到的c-Fos-IR细胞数量增加表明，参与厌恶记忆和焦虑的SUM中的神经活动变化与母性行为的维持有关。
