Abbas Farishta Reza, Robert Céline, Turcot Olivier, Thomas Sébastien, Vanni Matthieu P, Bouchard Jean-François, Casanova Christian
Laboratoire des Neurosciences de la Vision École d'optométrie, Université de Montréal, Montréal, Québec, Canada.
Laboratoire de Neuropharmacologie, École d'optométrie, Université de Montréal, Québec, Canada.
Invest Ophthalmol Vis Sci. 2015 Dec;56(13):7697-707. doi: 10.1167/iovs.15-17690.
The endocannabinoids (eCBs) and their receptors are expressed in the cortex of developing animals where they act as a neuromodulating system during critical stages of brain development such as cell proliferation and migration, and axon guidance. Little is known on the impact of the cannabinoid system on cortical map formation and receptive field properties of cortical sensory neurons. The present study evaluates in vivo the functional organization of the primary visual cortex (V1) of mice lacking cannabinoid CB1R receptor (cnr1-/-).
Using optical imaging of intrinsic signals, azimuth, and elevation maps of cnr1-/- mice were compared with their wild-type littermates (cnr1+/+).
Topographic maps were affected in mutant mice as they exhibited narrower visual field and changes in the shape of V1. CB1R exerted its action in an axis dependent manner as all changes were observed in the azimuth axis. Spatial frequency and contrast sensitivity were also compared between the two groups. Both properties were affected by the chronic lacking of CB1R as mutant mice exhibited a significantly lower contrast sensitivity as well as lower spatial frequency selectivity.
Taken together, these results suggest an important role for CB1R in cortical map formation. Our results also clearly demonstrate the impact of CB1R in the development of visual properties of primary visual cortex neurons. Because psychoactive effects of cannabis consumption on visual experience are mediated mainly through CB1R, our results could possibly explain neuronal mechanisms involved in those perceptual changes.
内源性大麻素（eCBs）及其受体在发育中动物的皮质中表达，在大脑发育的关键阶段，如细胞增殖、迁移和轴突导向过程中，它们作为一种神经调节系统发挥作用。关于大麻素系统对皮质图谱形成和皮质感觉神经元感受野特性的影响，目前所知甚少。本研究在体内评估了缺乏大麻素CB1R受体（cnr1-/-）的小鼠初级视觉皮质（V1）的功能组织。
利用内在信号的光学成像，将cnr1-/-小鼠的方位和仰角图谱与其野生型同窝小鼠（cnr1+/+）进行比较。
突变小鼠的地形图受到影响，因为它们的视野变窄且V1形状发生改变。CB1R以轴依赖性方式发挥作用，因为所有变化都出现在方位轴上。还比较了两组之间的空间频率和对比敏感度。由于突变小鼠表现出显著更低的对比敏感度以及更低的空间频率选择性，这两种特性都受到CB1R长期缺乏的影响。
综上所述，这些结果表明CB1R在皮质图谱形成中起重要作用。我们的结果还清楚地证明了CB1R对初级视觉皮质神经元视觉特性发育的影响。由于大麻消费对视觉体验的精神活性作用主要通过CB1R介导，我们的结果可能解释了这些感知变化所涉及的神经元机制。
