Department of Psychology, Macquarie University, North Ryde, NSW, Australia.
Centre for Emotional Health, Macquarie University, North Ryde, NSW, Australia.
J Neuroendocrinol. 2020 Jun;32(6):e12861. doi: 10.1111/jne.12861. Epub 2020 Jun 3.
The early postnatal period is a time of tremendous change for the dam and her offspring. During this time, environmental insults such as repeated stress exposure can have detrimental effects. In research that has focused on the effect of postnatal stress exposure on the dams, conflicting changes in maternal care and anxiety-like behaviour have been reported. Additionally, changes to hypothalamic neuropeptides that are crucially involved in the transition to motherhood and stress regulation, namely oxytocin and corticotrophin-releasing factor (CRF), have not been examined. Accordingly, the present study aimed to determine (i) whether repeated postpartum stress increases engagement in maternal care behaviours and anxiety-like behaviour and (ii) whether these behavioural changes correspond with changes to CRF- or oxytocin-immunoreactive (-IR) cells in the paraventricular nucleus (PVN) of the hypothalamus. A non-lactating group was also included to control for the effects of lactation on anxiety and the hypothalamic neuroendocrine system. Following the birth of their litters, Long-Evans dams were separated from their pups from postnatal day (PND) 1 to PND21 for either 15 minutes (maternal separation [MS]15) or 6 hours (MS360). Maternal behaviours were recorded for 30 minutes on select PNDs following the separation. On PND22, dams were exposed to the elevated plus maze, brains were collected, and immunofluorescence analysis of PVN oxytocin- and CRF-IR cells was conducted. Our findings demonstrate that prolonged maternal separation altered typical maternal behaviours and reduced anxiety relative to MS15 dams. At the cellular level, oxytocin-IR cells in the caudal PVN were reduced in MS360 dams to a level similar to that in non-lactating controls, and PVN CRF-IR cells were reduced relative to both MS15 and non-lactating controls. Taken together, these data reveal the behavioural and neuronal changes that occur in the mother dam following repeated postnatal stress exposure.
产后早期是母鼠及其后代发生巨大变化的时期。在此期间，环境刺激如反复应激暴露可能会产生有害影响。在专注于产后应激暴露对母鼠影响的研究中，报道了母性行为和焦虑样行为发生冲突性变化。此外，尚未研究对产后应激暴露后下丘脑神经肽发生的变化，这些神经肽对向母亲身份的转变和应激调节至关重要，即催产素和促肾上腺皮质素释放因子（CRF）。因此，本研究旨在确定：（i）反复产后应激是否会增加母性行为和焦虑样行为的参与度；（ii）这些行为变化是否与下丘脑室旁核（PVN）中的 CRF-或催产素免疫反应（IR）细胞的变化相对应。还纳入了非哺乳期组以控制哺乳期对焦虑和下丘脑神经内分泌系统的影响。长爪沙鼠分娩后，从产后第 1 天（PND1）到第 21 天（PND21），将母鼠与其幼崽分开 15 分钟（母体分离 [MS]15）或 6 小时（MS360）。在分离后的特定 PND 日，记录 30 分钟的母性行为。在 PND22 日，将母鼠暴露于高架十字迷宫中，收集大脑，并对 PVN 催产素和 CRF-IR 细胞进行免疫荧光分析。我们的研究结果表明，与 MS15 母鼠相比，长时间的母体分离改变了典型的母性行为，并降低了焦虑水平。在细胞水平上，MS360 母鼠的尾侧 PVN 中的催产素-IR 细胞减少到与非哺乳期对照组相似的水平，而 PVN 的 CRF-IR 细胞则与 MS15 和非哺乳期对照组相比减少。综上所述，这些数据揭示了产后应激反复暴露后母鼠发生的行为和神经元变化。
