Department of Physiology and Program in Neuroscience, University of Maryland-Baltimore, MD 21201, USA.
Horm Behav. 2010 Sep;58(4):575-81. doi: 10.1016/j.yhbeh.2010.07.010. Epub 2010 Aug 3.
Maternal licking in rats affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Reduced maternal licking results in decreased motoneuron number, size, and dendritic length in the adult SNB, as well as deficits in adult male copulatory behavior. Our previous findings that licking-like tactile stimulation influences SNB dendritic development and upregulates Fos expression in the lumbosacral spinal cord suggest that afferent signaling is changed by differences in maternal stimulation. Oxytocin afferents from the hypothalamus are a possible candidate, given previous research that has shown oxytocin is released following sensory stimulation, oxytocin modulates excitability in the spinal cord, and is a pro-erectile modulator of male sex behavior. In this experiment, we used immunofluorescence and immediate early gene analysis to assess whether licking-like tactile stimulation of the perineum activated parvocellular oxytocinergic neurons in the hypothalamus in neonates. We also used enzyme immunoassay to determine whether this same stroking stimulation produced an increase in spinal oxytocin levels. We found that stroking increased Fos immunolabeling in small oxytocin-positive cells in the paraventricular nucleus of the hypothalamus, in comparison to unstroked or handled control pups. In addition, 60s of licking-like perineal stimulation produced a transient 89% increase in oxytocin levels in the lumbosacral spinal cord. Together, these results suggest that oxytocin afferent activity may contribute to the effects of early maternal care on the masculinization of the SNB and resultant male copulatory behavior.
母鼠舔舐会影响脊髓球海绵体神经核（SNB）的发育，SNB 是一种性二态运动核，控制与交配相关的阴茎反射。母鼠舔舐减少会导致成年 SNB 的运动神经元数量、大小和树突长度减少，以及成年雄性交配行为缺陷。我们之前的研究发现，类似舔舐的触觉刺激会影响 SNB 树突发育，并在上位脊髓上调 Fos 表达，这表明母体刺激的差异会改变传入信号。来自下丘脑的催产素传入纤维可能是一个候选者，因为之前的研究表明，感觉刺激会引发催产素释放，催产素调节脊髓兴奋性，并且是雄性性行为的促勃起调制器。在这项实验中，我们使用免疫荧光和即时早期基因分析来评估新生儿外阴部的类似舔舐触觉刺激是否会激活下丘脑的小细胞催产素能神经元。我们还使用酶联免疫吸附测定来确定相同的刺激是否会增加脊髓催产素水平。我们发现，与未刺激或处理对照组的幼鼠相比，刺激会增加下丘脑室旁核中小催产素阳性细胞的 Fos 免疫标记。此外，60 秒的类似舔舐外阴刺激会使腰骶段脊髓中的催产素水平短暂增加 89%。这些结果表明，催产素传入活动可能有助于早期母体照顾对 SNB 雄性化和随后的雄性交配行为的影响。
