Lenz Kathryn M, Graham M Dean, Parada Mayte, Fleming Alison S, Sengelaub Dale R, Monks D Ashley
Program in Neuroscience, Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA.
Dev Neurobiol. 2008 Mar;68(4):542-57. doi: 10.1002/dneu.20608.
Maternal licking of rat pups affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Maternal licking influences SNB motoneurons, with reductions in licking producing decreased SNB number, size, and dendritic length in adulthood. Reduced maternal licking also produces deficits in adult male copulatory behavior. In this experiment, we used an artificial rearing paradigm to assess the potential role of tactile stimulation in mediating the effects of maternal licking on the SNB neuromuscular system. During artificial rearing, pups were stroked with a paintbrush to mimic maternal licking, receiving low, medium, or high levels of daily stimulation. In adulthood, ex copula penile reflex behavior was tested and the morphology of SNB motoneurons assessed. SNB motoneurons were retrogradely labeled with cholera toxin-conjugated HRP and dendritic arbor was reconstructed in three dimensions. Animals that received low levels of stimulation showed deficits in penile reflexes relative to maternally reared controls, including a longer latency to erection, fewer cup erections, and fewer erection clusters. SNB dendritic morphology was also shaped by stimulation condition, with animals that received low or medium levels of stimulation showing an average 27% reduction in dendritic length. In addition, several reflex behaviors were significantly correlated with dendritic length, including latency to first erection, percent of cup erections, and number of erection clusters. These results suggest that tactile stimulation provided by maternal licking mediates some of the effects of maternal care on the development of male copulatory behavior.
母鼠对幼鼠的舔舐会影响球海绵体肌脊髓核（SNB）的发育，SNB是一个具有性别差异的运动核，控制着与交配相关的阴茎反射。母鼠的舔舐会影响SNB运动神经元，舔舐减少会导致成年后SNB的数量、大小和树突长度减少。母鼠舔舐减少还会导致成年雄性交配行为出现缺陷。在本实验中，我们采用人工饲养范式来评估触觉刺激在介导母鼠舔舐对SNB神经肌肉系统影响方面的潜在作用。在人工饲养期间，用画笔轻抚幼鼠以模拟母鼠的舔舐，使其接受低、中、高三种不同水平的每日刺激。成年后，测试离体阴茎反射行为并评估SNB运动神经元的形态。用霍乱毒素结合的辣根过氧化物酶对SNB运动神经元进行逆行标记，并对树突分支进行三维重建。与由母鼠抚养的对照组相比，接受低水平刺激的动物阴茎反射存在缺陷，包括勃起潜伏期延长、杯状勃起次数减少和勃起簇数量减少。SNB的树突形态也受刺激条件的影响，接受低水平或中等水平刺激的动物树突长度平均减少27%。此外，一些反射行为与树突长度显著相关，包括首次勃起潜伏期、杯状勃起百分比和勃起簇数量。这些结果表明，母鼠舔舐提供的触觉刺激介导了母性关怀对雄性交配行为发育的部分影响。
