Wall Nicholas R, De La Parra Mauricio, Sorokin Jordan M, Taniguchi Hiroki, Huang Z Josh, Callaway Edward M
Systems Neurobiology Laboratories, Salk Institute for Biological Studies, La Jolla, California 92037, Neurosciences Graduate Program, University of California, San Diego, La Jolla, California 92093.
Systems Neurobiology Laboratories, Salk Institute for Biological Studies, La Jolla, California 92037.
J Neurosci. 2016 Apr 6;36(14):4000-9. doi: 10.1523/JNEUROSCI.3967-15.2016.
Cortical inhibition is mediated by diverse inhibitory neuron types that can each play distinct roles in information processing by virtue of differences in their input sources, intrinsic properties, and innervation targets. Previous studies in brain slices have demonstrated considerable cell-type specificity in laminar sources of local inputs. In contrast, little is known about possible differences in distant inputs to different cortical interneuron types. We used the monosynaptic rabies virus system, in conjunction with mice expressing Cre recombinase in either parvalbumin-positive, somatostatin-positive (SST+), or vasoactive intestinal peptide-positive (VIP+) neurons, to map the brain-wide input to the three major nonoverlapping classes of interneurons in mouse somatosensory cortex. We discovered that all three classes of interneurons received considerable input from known cortical and thalamic input sources, as well as from probable cholinergic cells in the basal nucleus of Meynert. Despite their common input sources, these classes differed in the proportion of long-distance cortical inputs originating from deep versus superficial layers. Similar to their laminar differences in local input, VIP+ neurons received inputs predominantly from deep layers while SST+ neurons received mostly superficial inputs. These classes also differed in the amount of input they received. Cortical and thalamic inputs were greatest onto VIP+ interneurons and smallest onto SST+ neurons.
These results indicate that all three major interneuron classes in the barrel cortex integrate both feedforward and feedback information from throughout the brain to modulate the activity of the local cortical circuit. However, differences in laminar sources and magnitude of distant cortical input suggest differential contributions from cortical areas. More input to vasoactive intestinal peptide-positive (VIP+) neurons than to somatostatin-positive (SST+) neurons suggests that disinhibition of the cortex via VIP+ cells, which inhibit SST+ cells, might be a general feature of long-distance corticocortical and thalamocortical circuits.
皮质抑制由多种抑制性神经元类型介导，这些神经元凭借其输入源、内在特性和支配靶点的差异，在信息处理中各自发挥独特作用。先前在脑片上的研究已证明局部输入的层状来源具有相当大的细胞类型特异性。相比之下，对于不同皮质中间神经元类型的远距离输入可能存在的差异知之甚少。我们使用单突触狂犬病病毒系统，结合在小白蛋白阳性、生长抑素阳性（SST+）或血管活性肠肽阳性（VIP+）神经元中表达Cre重组酶的小鼠，来绘制小鼠体感皮层中三类主要不重叠中间神经元的全脑输入图谱。我们发现，这三类中间神经元均从已知的皮质和丘脑输入源以及梅纳特基底核中可能的胆碱能细胞接收大量输入。尽管它们有共同的输入源，但这些类别在源自深层与浅层的远距离皮质输入比例上存在差异。与它们在局部输入中的层状差异类似，VIP+神经元主要接收来自深层的输入，而SST+神经元大多接收浅层输入。这些类别在接收的输入量上也存在差异。皮质和丘脑输入到VIP+中间神经元的量最大，到SST+神经元的量最小。
这些结果表明，桶状皮层中的所有三类主要中间神经元整合了来自全脑的前馈和反馈信息，以调节局部皮质回路的活动。然而，远距离皮质输入的层状来源和大小的差异表明皮质区域的贡献不同。血管活性肠肽阳性（VIP+）神经元比生长抑素阳性（SST+）神经元接收更多输入，这表明通过抑制SST+细胞的VIP+细胞对皮质的去抑制可能是远距离皮质-皮质和丘脑-皮质回路的一个普遍特征。
