Machín Raquel, Pérez-Cejuela César G, Bjugn Roger, Avendaño Carlos
Department of Anatomy, Histology and Neuroscience, Autonoma University, School of Medicine, Madrid, Spain, and Department of Pathology, Ullevål University Hospital, Oslo, Norway.
Brain Res. 2006 Aug 30;1107(1):104-10. doi: 10.1016/j.brainres.2006.05.096. Epub 2006 Jul 5.
Whisker trimming deprives the cortical barrel field from the patterned sensory input that derives from active touch but leaves passive tactile signals unaltered. We have studied in the rat barrel field, by stereological procedures, the effects of a sustained period of unilateral deprivation by whisker clipping during adolescence and early adulthood on (1) the surface density (SV) of asymmetric synapses, as determined from measuring the presynaptic membrane specializations, and (2) the numerical density of asymmetric synaptic profiles (NA), classified according to their postsynaptic target and their apparent curvature. Compared to control rats, the procedure did not change the overall volume of the region, the volume fraction occupied by each cortical layer, or the volume fraction occupied by unmyelinated axons and boutons. However, the deprived barrel cortex displayed an increase in SV in layers I and II, and an increase in NA in layer I and in the cortex as a whole, mainly due to an increase in profiles with a convex shape. Layer IV was the least affected by the deprivation. These results point to a net increase, rather than a decrease, of excitatory synapses in the deprived cortex, which could result from a deprivation-induced decrease in the rate of normal synapse loss. This effect occurs specifically in superficial layers, more involved in intracortical and cortico-cortical, rather than thalamo-cortical, processing.
修剪触须会使皮质桶状区失去源于主动触摸的模式化感觉输入，但不会改变被动触觉信号。我们通过体视学方法在大鼠桶状区研究了青春期和成年早期单侧持续剪须剥夺对以下两方面的影响：（1）不对称突触的表面密度（SV），通过测量突触前膜特化来确定；（2）不对称突触轮廓的数量密度（NA），根据其突触后靶点和明显曲率进行分类。与对照大鼠相比，该操作并未改变该区域的总体积、各皮质层所占的体积分数，或无髓鞘轴突和终扣所占的体积分数。然而，被剥夺的桶状皮质在I层和II层的SV增加，在I层和整个皮质中的NA增加，主要是由于凸形轮廓的增加。IV层受剥夺的影响最小。这些结果表明，被剥夺皮质中兴奋性突触的净增加而非减少，这可能是由于剥夺导致正常突触丢失率降低所致。这种效应特别发生在浅层，浅层更多地参与皮质内和皮质 - 皮质的处理，而非丘脑 - 皮质的处理。
