Postsynaptic structures of axon terminals of cortical double bouquet cells

Research Project

Project/Area Number	14580782
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Neuroscience in general
Research Institution	Okazaki National Research Institutes
Principal Investigator	KUBOTA Yoshiyuki Okazaki National Research Institutes, National Institute for Physiological Sciences, Division of Cerebral Circuitry, Associate Professor, 生理学研究所, 助教授 (90192567)
Project Period (FY)	2002 – 2003
Project Status	Completed (Fiscal Year 2003)
Budget Amount *help	¥3,600,000 (Direct Cost: ¥3,600,000) Fiscal Year 2003: ¥1,400,000 (Direct Cost: ¥1,400,000) Fiscal Year 2002: ¥2,200,000 (Direct Cost: ¥2,200,000)
Keywords	synapse / microcircuits / calcium binding protein / 3 dimensional / corticotrophin releasing factor / cerebral cortex / axon terminal / spine / カルレチニン / 主成分分析 / クラスター分析
Research Abstract	Cortical GABAergic nonpyramidal (NP) cells regulate activities of cortical pyramidal cells. We investigated synaptic connections made by double bouquet (DB) cells, a subtype of NP cells. Using the double immunohistochemistry, calretinin (CR) and corticotrophin releasing factor (CRF) were found in largely separate subgroups of DB cells in layers II/III. Thus, CR-and CRF-positive DB cells may be considered as different cell subtypes. We further studied postsynaptic structures of these two subtypes of DB cells to see differences in their target structures. NP cells were identified in isolated slices of young rat frontal cortex by whole cell, current-clamp recording, followed by intracellular injection of biocytin. After immunostaining with antisera against CR and CRF, the cells were stained with DAB. The postsynaptic structures were reconstructed three-dimensionally from serial ultra-thin sections of the intracellulary-stained axon terminals of one chemically unidentified DB cell, two CR-DB cells and two CRF-DB cells. The unidentified cell and two CR-DB cells showed similar results. They innervated dendritic shafts (50-68%), spines (19-47%) and rarely somata (2-9%). The target spines usually had an asymmetrical input. This may indicate the DB cell specifically inhibits this excitatory input. Some target dendrites (30-37%) received many asymmetrical synapses on their shafts, which indicated dendrites of NP cells. The rest of the target dendrites (17-31%) were of both pyramidal and NP cells. The innervation targets of CRF-DB cells were slightly different. The dendritic shafts (63-73%) and spines (27-37%) were the major targets, but no somata were observed. The dendrites with many asymmetrical inputs were observed less (10-18%) and vertically elongated dendrites were identified frequently (20-30%). These observations indicated CR-and CRF-DB cell subtypes may be involved in distinct functions in cortical microcircuit.