Munetomo Arisa, Ishii Hirotaka, Miyamoto Takenori, Sakuma Yasuo, Kondo Yasuhiko
Laboratory of Behavior Neuroscience, Faculty of Science, Japan Women's University, Tokyo 112-8681, Japan.
J Reprod Dev. 2016;62(1):17-27. doi: 10.1262/jrd.2015-046. Epub 2015 Oct 9.
In the rat, induction of maternal behavior depends on the parity of the female. For example, nulliparous (NP) females need longer exposure to pups than multiparous (MP) or lactating (L) females to exhibit similar maternal behavior. In this study, we investigated the role of brain oxytocin in the approaching behavior of these female rats. Olfactory preferences for pup odors were examined for 8 consecutive days. Each preference test was followed by direct overnight exposure to pups. On the 8th day, MP and L, but not NP females showed robust pup-odor preferences. After the behavioral test, half of the females were exposed to pups for 2 h, whereas the other half were not. The females were then sacrificed to analyze brain oxytocin (OXT) and vasopressin (AVP) activities by cFos immunohistochemistry and to quantify their receptor mRNA expression using real-time PCR. In the paraventricular nucleus (PVN), the percentage of cFos-positive OXT neurons was significantly larger in MP and L females than in NP females after pup exposure. No significant differences were found in cFos expression in OXT neurons of the supraoptic nucleus (SON) or in AVP neurons of either the PVN or SON. Expression of OXT receptor mRNA in the medial preoptic area and amygdala of the control groups was also higher in MP females than in NP females. Finally, we demonstrated that infusion of OXT into the lateral ventricle of NP females promoted preferences for pup odors. These results indicate that puerperal and parental experiences enhance the responsiveness of OXT neurons in the PVN to pup stimuli and establish olfactory preferences for these odors in a parity-dependent manner.
在大鼠中，母性行为的诱导取决于雌性的生育状态。例如，未生育（NP）的雌性大鼠需要比经产（MP）或正在哺乳（L）的雌性大鼠更长时间接触幼崽，才能表现出类似的母性行为。在本研究中，我们调查了脑内催产素在这些雌性大鼠接近行为中的作用。连续8天检测对幼崽气味的嗅觉偏好。每次偏好测试后，直接让其过夜接触幼崽。在第8天，MP和L组的雌性大鼠表现出强烈的幼崽气味偏好，而NP组的雌性大鼠则没有。行为测试后，一半的雌性大鼠接触幼崽2小时，而另一半则不接触。然后处死雌性大鼠，通过cFos免疫组织化学分析脑内催产素（OXT）和加压素（AVP）的活性，并使用实时PCR定量其受体mRNA表达。在室旁核（PVN）中，幼崽接触后，MP和L组雌性大鼠中cFos阳性OXT神经元的百分比显著高于NP组雌性大鼠。在视上核（SON）的OXT神经元或PVN和SON的AVP神经元的cFos表达中未发现显著差异。对照组中，MP组雌性大鼠内侧视前区和杏仁核中OXT受体mRNA的表达也高于NP组雌性大鼠。最后，我们证明向NP组雌性大鼠侧脑室注入OXT可促进对幼崽气味的偏好。这些结果表明，产后和育儿经历增强了PVN中OXT神经元对幼崽刺激的反应性，并以生育状态依赖的方式建立了对这些气味的嗅觉偏好。
