Motherhood entails changes in behavior with increased motivation for pups, induced in part by pregnancy hormones acting upon the brain. This work explores whether this alters sensory processing of pup-derived chemosignals. To do so, we analyse the expression of immediate early genes (IEGs) in the vomeronasal organ (VNO; Egr1) and centers of the olfactory and vomeronasal brain pathways (cFos) in virgin and late-pregnant females exposed to pups, as compared to buttons (socially neutral control). In pup-exposed females, we quantified diverse behaviors including pup retrieval, sniffing, pup-directed attack, nest building and time in nest or on nest, as well as time off nest. Pups induce Egr1 expression in the VNO of females, irrespective of their physiological condition, thus suggesting the existence of VNO-detected pup chemosignals. A similar situation is found in the accessory olfactory bulb (AOB) and posteromedial part of the medial bed nucleus of the stria terminalis (BSTMPM). By contrast, in the medial amygdala and posteromedial cortical amygdala (PMCo), responses to pups-vs-buttons are different in virgin and late-pregnant females, thus suggesting altered sensory processing during late pregnancy. The olfactory system also shows changes in sensory processing with pregnancy. In the main olfactory bulbs, as well as the anterior and posterior piriform cortex, buttons activate cFos expression in virgins more than in pregnant females. By contrast, in the anterior and especially posterior piriform cortex, pregnant females show more activation by pups than buttons. Correlation between IEGs expression and behavior suggests the existence of two vomeronasal subsystems: one associated to pup care (with PMCo as its main center) and another related to pup-directed aggression observed in some pregnant females (with the BSTMPM as the main nucleus). Our data also suggest a coactivation of the olfactory and vomeronasal systems during interaction with pups in pregnant females.

孕育需要改变行为，增加幼仔的动力，这部分是由作用在大脑上的妊娠激素引起的。这项工作探讨了这是否会改变幼犬衍生的化学信号的感觉处理。为此，我们分析了暴露于幼崽的处女和晚期孕妇在鼻息肉器官（VNO; Egr1）中的早期早期基因（IEG）的表达以及嗅觉和犁鼻脑通路（cFos）的中心，按钮（社会中性控制）。在暴露于幼崽的雌性中，我们量化了各种行为，包括幼崽的取回，嗅探，针对幼犬的攻击，筑巢以及筑巢或筑巢的时间以及筑巢的时间。幼犬无论其生理状况如何，均可在雌性VNO中诱导Egr1表达，因此表明存在VNO检测到的幼犬化学信号。在末梢纹状体内侧床核的副嗅球（AOB）和后内侧部分（BSTMPM）中也发现了类似情况。相比之下，在内侧杏仁核和后内侧皮层杏仁核（PMCo）中，初生和晚期孕妇对小白鼠对纽扣的反应不同，因此提示妊娠后期感觉过程改变。嗅觉系统还显示出怀孕后感觉过程的变化。在主要的嗅球以及梨状肌的前部和后部，纽扣在处女中激活cFos的表达比怀孕女性更多。相比之下，在梨形前皮层，尤其是后侧的梨形皮层中，与按钮相比，怀孕的雌性幼崽表现出更多的激活作用。IEGs表达与行为之间的相关性表明存在两个犁鼻子系统：一个与幼仔护理有关（以PMCo为主要中心），另一种与某些孕妇（以BSTMPM为主要核）中观察到的针对幼犬的侵略有关。我们的数据还表明，在与怀孕女性的幼崽互动期间，嗅觉和犁鼻系统会共同激活。