Department of Biology and Neuroscience and Cognitive Sciences Program, University of Maryland, College Park, MD 20740, USA.
Department of Bioengineering and Biomedical Engineering, University of Maryland, College Park, MD 20740, USA.
Int J Mol Sci. 2022 Feb 23;23(5):2438. doi: 10.3390/ijms23052438.
The deletion of matrix metalloproteinase MMP9 is combined here with chronic monocular deprivation (cMD) to identify the contributions of this proteinase to plasticity in the visual system. Calcium imaging of supragranular neurons of the binocular region of primary visual cortex (V1b) of wild-type mice revealed that cMD initiated at eye opening significantly decreased the strength of deprived-eye visual responses to all stimulus contrasts and spatial frequencies. cMD did not change the selectivity of V1b neurons for the spatial frequency, but orientation selectivity was higher in low spatial frequency-tuned neurons, and orientation and direction selectivity were lower in high spatial frequency-tuned neurons. Constitutive deletion of MMP9 did not impact the stimulus selectivity of V1b neurons, including ocular preference and tuning for spatial frequency, orientation, and direction. However, MMP9 mice were completely insensitive to plasticity engaged by cMD, such that the strength of the visual responses evoked by deprived-eye stimulation was maintained across all stimulus contrasts, orientations, directions, and spatial frequencies. Other forms of experience-dependent plasticity, including stimulus selective response potentiation, were normal in MMP9 mice. Thus, MMP9 activity is dispensable for many forms of activity-dependent plasticity in the mouse visual system, but is obligatory for the plasticity engaged by cMD.
这里将基质金属蛋白酶 MMP9 的缺失与慢性单侧眼剥夺（cMD）相结合，以确定这种蛋白酶对视觉系统可塑性的贡献。对野生型小鼠初级视觉皮层（V1b）的双眼区域的超颗粒神经元进行钙成像显示，在睁眼时开始的 cMD 显著降低了剥夺眼对所有刺激对比度和空间频率的视觉反应强度。cMD 并没有改变 V1b 神经元对空间频率的选择性，但在低空间频率调谐神经元中，方向选择性更高，而在高空间频率调谐神经元中，方向和方向选择性更低。MMP9 的组成性缺失不会影响 V1b 神经元的刺激选择性，包括眼偏好和对空间频率、方向和方向的调谐。然而，MMP9 小鼠对 cMD 引起的可塑性完全不敏感，以至于由剥夺眼刺激引起的视觉反应的强度在所有刺激对比度、方向、方向和空间频率下都保持不变。MMP9 小鼠中的其他形式的经验依赖性可塑性，包括刺激选择性反应增强，是正常的。因此，MMP9 活性对于小鼠视觉系统中的许多形式的活动依赖性可塑性是可有可无的，但对于 cMD 引起的可塑性是必需的。
