Princeton Neuroscience Institute, Psychology Department, Princeton University, Princeton, NJ 08540, USA.
Princeton Neuroscience Institute, Psychology Department, Princeton University, Princeton, NJ 08540, USA.
Neurobiol Learn Mem. 2018 Nov;155:50-59. doi: 10.1016/j.nlm.2018.06.008. Epub 2018 Jun 23.
Increases in the number and/or the size of dendritic spines, sites of excitatory synapses, have been linked to different types of learning as well as synaptic plasticity in several brain regions, including the hippocampus, sensory cortex, motor cortex, and cerebellum. By contrast, a previous study reported that training on a maze task requiring the dorsal striatum has no effect on medium spiny neuron dendritic spines in this area. These findings might suggest brain region-specific differences in levels of plasticity as well as different cellular processes underlying different types of learning. No previous studies have investigated whether dendritic spine density changes may be localized to specific subpopulations of medium spiny neurons, nor have they examined dendritic spines in rats trained on a dorsolateral striatum-dependent maze task in comparison to rats exposed to the same type of maze in the absence of training. To address these questions further, we labeled medium spiny neurons with the lipophilic dye DiI and stained for the protein product of immediate early gene zif 268, an indirect marker of neuronal activation, in both trained and untrained groups. We found a small but significant increase in dendritic spine density on medium spiny neurons of the dorsolateral striatum after short-term intensive training, along with robust increases in the density of spines with mushroom morphology coincident with reductions in the density of spines with thin morphology. However, these results were not associated with zif 268 expression. Our findings suggest that short-term intensive training on a dorsolateral striatum-dependent maze task induces rapid increases in dendritic spine density and maturation on medium spiny neurons of the dorsolateral striatum, an effect which may contribute to early acquisition of the learned response in maze training.
树突棘数量和/或大小的增加与不同类型的学习以及包括海马体、感觉皮层、运动皮层和小脑在内的几个脑区的突触可塑性有关。相比之下，先前的一项研究报告称，在需要背侧纹状体的迷宫任务上进行训练对该区域的中型多棘神经元树突棘没有影响。这些发现可能表明大脑区域之间存在可塑性水平的差异，以及不同类型的学习所涉及的不同细胞过程。以前没有研究调查过树突棘密度的变化是否可能局限于中型多棘神经元的特定亚群，也没有研究过在没有训练的情况下接受相同类型迷宫暴露的大鼠与在背外侧纹状体依赖的迷宫任务上接受训练的大鼠相比，背外侧纹状体的树突棘。为了进一步解决这些问题，我们用亲脂性染料 DiI 标记中型多棘神经元，并对即时早期基因 zif 268 的蛋白质产物进行染色，zif 268 是神经元激活的间接标志物，在训练和未训练组中均进行了检测。我们发现，经过短期强化训练后，背外侧纹状体中型多棘神经元的树突棘密度略有但显著增加，同时蘑菇状形态的棘密度显著增加，而细形态的棘密度降低。然而，这些结果与 zif 268 的表达无关。我们的发现表明，在背外侧纹状体依赖的迷宫任务上进行短期强化训练会导致背外侧纹状体中型多棘神经元的树突棘密度和成熟度迅速增加，这一效应可能有助于在迷宫训练中早期获得学习反应。
