Analysis of the local neural circuit in the central nervous system

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1. Intracortical connections were examined by combining intracellular staining with Golgi-like retrograde labeling of corticofugal neurons. In the motor cortex, 15.2% or 3.8% of varicosities of axon collaterals of the reconstructed layer III pyramidal neurons were apposed to dendrites of corticospinal or corticothalamic neurons, respectively. On the other hand, corticospinal neurons received many collateral inputs from all the cortical layers, suggesting the convergence of information to produce motor output.2. We have developed adenovirus and Sindbis virus vectors, with which neurons were transduced to express membrane-targeted green fluorescent protein (pGFP). The infected neurons were visualized by fluorescence or immunocytochemistry in a Golgi-atain fashion.3. We developed a transgenic mouse line which produce pGFP under a control of Kv3.1 potassium channel promoter. We are now analyzing the specificity of expression in GABAergic and thalamic relay neurons.4. Antibodies to vesicula … More r glutamate transporters (VGluTs) were produced and applied to immunocytochemistry of the brain. VGluT1 and VGluT2 were used by cortical pyramidal neurons and thalamic relay neurons, respectively. Cortical and thalamic excitatory inputs were thus labeled with VGluT1 and VGluT2 selectively in the cerebral cortex and striatum. By combining this VGluT immunostaining with the viral labeling method described above, we are now investigating how many cortical and thalamic inputs enter a cortical or striatal neuron.5. We reported a third striatofugal pathway, which were characterized by the expression of neurokinin B and projection to the substantia innominata (SI). Some GABAergic SI neurons were found to project to the cerebral cortex and express receptor for neurokin B. Since neurokinin B released from striato-innominatal neurons induced facilitatory effects on the GABAergic innominatocortical neurons, the third pathway may control the cortical activity through those innominatocortical neurons. Less