Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Neuroscience. 2010 Sep 15;169(4):1651-61. doi: 10.1016/j.neuroscience.2010.06.011. Epub 2010 Jun 11.
Exposure to cannabis impairs cognitive functions reliant on the circuitry of the dorsolateral prefrontal cortex (DLPFC) and increases the risk of schizophrenia. The actions of cannabis are mediated via the brain cannabinoid 1 receptor (CB1R), which in rodents is heavily localized to the axon terminals of cortical GABA basket neurons that contain cholecystokinin (CCK). Differences in the laminar distribution of CB1R-immunoreactive (IR) axons have been reported between rodent and monkey neocortex, suggesting that the cell type(s) containing CB1Rs, and the synaptic targets of CB1R-IR axon terminals, may differ across species; however, neither the relationship of CB1Rs to CCK-containing interneurons, nor the postsynaptic targets of CB1R and CCK axon terminals, have been examined in primate DLPFC. Consequently, we compared the distribution patterns of CB1R- and CCK-IR structures, determined the proportions of CB1R and CCK neurons that were dual-labeled, and identified the synaptic types and postsynaptic targets of CB1R- and CCK-IR axon terminals in macaque monkey DLPFC. By light microscopy, CB1R- and CCK-IR axons exhibited a similar laminar distribution, with their greatest densities in layer 4. Dual-label fluorescence experiments demonstrated that 91% of CB1R-IR neurons were immunopositive for CCK, whereas only 51% of CCK-IR neurons were immunopositive for CB1R. By electron microscopy, all synapses formed by CB1R-IR axon terminals were symmetric, whereas CCK-IR axon terminals formed both symmetric (88%) and asymmetric (12%) synapses. The primary postsynaptic target of both CB1R- and CCK-IR axon terminals forming symmetric synapses was dendritic shafts (81-88%), with the remainder targeting cell bodies or dendritic spines. Thus, despite species differences in laminar distribution, CB1Rs are principally localized to CCK basket neuron axons in both rodent neocortex and monkey DLPFC. These axons target the perisomatic region of pyramidal neurons, providing a potential anatomical substrate for the impaired function of the DLPFC associated with cannabis use and schizophrenia.
大麻暴露会损害依赖背外侧前额叶皮质(DLPFC)回路的认知功能,并增加精神分裂症的风险。大麻的作用是通过大脑中的大麻素 1 受体(CB1R)介导的,在啮齿动物中,该受体主要位于含有胆囊收缩素(CCK)的皮质 GABA 篮状神经元的轴突末梢。据报道,在啮齿动物和猴子新皮层之间,CB1R-免疫反应(IR)轴突的层分布存在差异,这表明包含 CB1R 的细胞类型和 CB1R-IR 轴突末梢的突触靶标可能在不同物种之间存在差异;然而,CB1R 与 CCK 阳性中间神经元的关系,以及 CB1R 和 CCK 轴突末梢的突触后靶标,尚未在灵长类动物 DLPFC 中进行研究。因此,我们比较了 CB1R 和 CCK-IR 结构的分布模式,确定了双重标记的 CB1R 和 CCK 神经元的比例,并确定了灵长类动物 DLPFC 中 CB1R 和 CCK-IR 轴突末梢的突触类型和突触后靶标。通过光镜,CB1R 和 CCK-IR 轴突表现出相似的层分布,在第 4 层密度最大。双重荧光实验表明,91%的 CB1R-IR 神经元对 CCK 呈免疫阳性,而只有 51%的 CCK-IR 神经元对 CB1R 呈免疫阳性。通过电子显微镜,CB1R-IR 轴突末梢形成的所有突触均为对称突触,而 CCK-IR 轴突末梢形成的突触既有对称突触(88%),也有不对称突触(12%)。形成对称突触的 CB1R 和 CCK-IR 轴突末梢的主要突触后靶标是树突干(81-88%),其余则靶向胞体或树突棘。因此,尽管在层分布上存在种间差异,但在啮齿动物新皮层和猴子 DLPFC 中,CB1R 主要定位于 CCK 篮状神经元轴突。这些轴突靶向锥体神经元的胞体周围区域,为大麻使用和精神分裂症相关的 DLPFC 功能障碍提供了潜在的解剖学基础。