Department of Psychology, University of Toronto at Mississauga, 3359 Mississauga Rd N, Mississauga, ON, Canada L5L 1C6.
Horm Behav. 2011 Nov;60(5):632-43. doi: 10.1016/j.yhbeh.2011.08.016. Epub 2011 Sep 22.
Postpartum rats that had been previously raised in an artificial rearing (AR) apparatus, without their mothers or siblings during the preweaning period, show altered maternal responses towards their own offspring in adulthood. In mother-reared (MR) rats, nucleus accumbens (NAC) dopamine (DA) responses to pups evoke a robust sustained rise during the postpartum period and following treatment with estrogen/progesterone parturient-like hormones (Afonso et al., 2009). These MR females had siblings that received AR rearing with varying amounts of preweaning tactile stimulation (ARmin; ARmax). The present study examined NACshell DA responses to pup and food stimuli in these AR rats, and statistically compared them to their MR siblings. Microdialysis samples were collected from adult (90 days postnatal) AR females in different parity states (cycling vs. postpartum, Exp. 1), or after ovariectomy with different hormone treatments (sham vs. hormone, Exp. 2. After basal sample collection, pup and then food stimuli were individually presented to the females in the dialysis chamber. As with their MR siblings, basal DA concentrations were lower and pup-evoked DA responses greater in hormonally-primed AR females than in non-primed AR controls. Compared to their postpartum MR sisters (Exp. 1), AR rats had increased basal DA levels, reduced pup related DA elevations, and disrupted maternal behavior. The postpartum AR impairment in pup-evoked DA was reversed by additional pre-weaning tactile stimulation. Exogenous hormones (Exp. 2) eliminated AR impairments on pup-evoked DA responses. Although MR and AR siblings had comparable DA responses to food stimuli, upon reanalyzing MR data it was found that only postpartum dams had DA responses to pups greater than to food. These data suggest that that the hormonally induced suppression of basal DA levels may reflect saliency of pups which was greater in MR than in AR dams. Preweaning tactile stimulation could partially reverse these effects only in naturally cycling or parturient animals.
在哺乳期前，曾被置于人工养育（AR）设备中、没有与母亲或兄弟姐妹接触的产后大鼠，其成年后对自身幼崽的母性行为会发生改变。在经母体养育（MR）的大鼠中，伏隔核（NAC）中的多巴胺（DA）对幼崽的反应在产后期间以及在接受雌激素/孕激素分娩样激素治疗后会出现强烈且持续的上升（Afonso 等人，2009）。这些 MR 雌性大鼠有其兄弟姐妹，这些兄弟姐妹在哺乳期前接受了不同程度的 AR 养育和触觉刺激（ARmin；ARmax）。本研究检测了这些 AR 大鼠的 NAC 壳 DA 对幼崽和食物刺激的反应，并将其与 MR 兄弟姐妹进行了统计学比较。在不同的产仔状态（发情周期对产后，实验 1）或卵巢切除术后接受不同激素处理（假手术对照对激素，实验 2）下，从成年（产后 90 天）AR 雌性大鼠中收集微透析样本。在收集基础样本后，将幼崽和食物刺激分别呈现在透析室中的雌性大鼠面前。与 MR 姐妹一样，经激素预处理的 AR 雌性大鼠的基础 DA 浓度较低，对幼崽的 DA 反应较大，而未经激素预处理的 AR 对照大鼠则相反。与产后的 MR 姐妹（实验 1）相比，AR 大鼠的基础 DA 水平升高，对幼崽相关的 DA 升高反应降低，且母性行为受到破坏。额外的哺乳期前触觉刺激可以逆转产后 AR 大鼠幼崽诱发的 DA 损伤。外源性激素（实验 2）消除了 AR 对幼崽诱发的 DA 反应的损伤。尽管 MR 和 AR 姐妹对食物刺激的 DA 反应相似，但重新分析 MR 数据发现，只有产后的母鼠对幼崽的 DA 反应大于对食物的反应。这些数据表明，激素诱导的基础 DA 水平抑制可能反映了幼崽的显著性，而在 MR 母鼠中比在 AR 母鼠中更为显著。在自然发情或分娩的动物中，哺乳期前的触觉刺激可能部分逆转这些影响。
