Brain Science Institute, RIKEN, Wako 351-0198, Japan, Department of Genetic and Behavioral Neuroscience, Graduate School of Medicine, Gunma University, Maebashi 371-8511 Japan.
J Neurosci. 2010 Oct 20;30(42):14261-72. doi: 10.1523/JNEUROSCI.2979-10.2010.
The developmental period when neuronal responses are modified by visual experience is reported to start and end earlier in layer 4 than in layer 2/3 of the visual cortex, and the maturation of GABAergic inhibitory circuits is suggested to determine the timing of this period. Here, we examine whether the laminar difference in such timing corresponds to a difference in the time course of the functional maturation of GABAergic synaptic transmission to star pyramidal and pyramidal cells in layers 4 and 2/3, respectively, of the mouse visual cortex and whether the development of the strength of GABAergic transmission is affected by visual deprivation in a laminar-specific manner. Our analysis of developmental changes in inhibitory postsynaptic currents of star pyramidal and pyramidal cells evoked by electrical stimulation of afferents or action potentials of fast-spiking GABAergic neurons revealed that there was a sequential maturation of GABAergic function from layers 4 to 2/3. The maturation of inhibition in layer 4 occurred at postnatal week 3, which preceded by 1 week that of layer 2/3. Visual deprivation by dark rearing arrested the functional development of GABAergic transmission in layer 2/3, whereas dark rearing was not so effective in layer 4. GABAergic synapses in layer 2/3 were sensitive to an agonist for cannabinoid type 1 receptors and not normally matured in receptor knock-out mice, whereas those in layer 4 were not so. These results suggest laminar-specific maturation of inhibition and susceptibility to visual deprivation, which may be related to the laminar difference in sensitivity to endocannabinoids.
神经元反应受视觉经验影响的发育阶段据报道在视皮层的第 4 层比在第 2/3 层开始和结束得更早，并且 GABA 能抑制性回路的成熟被认为决定了这段时期的时间。在这里，我们研究了这种时间上的分层差异是否对应于 GABA 能突触传递到视皮层第 4 层和第 2/3 层的星形锥体细胞和锥体细胞的功能成熟时间进程的差异，以及 GABA 能传递的发展是否受到视觉剥夺的分层特异性影响。我们分析了通过刺激传入纤维或快速放电 GABA 能神经元的动作电位诱发的星形锥体细胞和锥体细胞的抑制性突触后电流的发育变化，结果表明 GABA 能功能从第 4 层到第 2/3 层依次成熟。第 4 层的抑制成熟发生在出生后第 3 周，比第 2/3 层早 1 周。暗饲养导致 GABA 能传递的功能发育在第 2/3 层受阻，而暗饲养在第 4 层效果不那么明显。第 2/3 层的 GABA 能突触对大麻素 1 型受体激动剂敏感，并且在受体敲除小鼠中不能正常成熟，而第 4 层的则不然。这些结果表明抑制的分层特异性成熟和对视觉剥夺的敏感性，这可能与内源性大麻素敏感性的分层差异有关。
