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信州大学博士（医学）・学位論文・平成24年3月31日授与（甲第915号）・関口泰之, The lateral olfactory tract (LOT) is a central olfactory pathway, and efferent projections from the olfactory bulb are conveyed to the olfactory-related cortical structures via the LOT. The purpose of the present study is to determine the exact site of the LOT causing functional impairment in animals. After ablation of the right olfactory bulb, rats received rostrocaudal transection injuries on the left LOT at different levels between the olfactory bulb and the middle cerebral artery. Olfactory function of LOT-transected rats was studied by examining their olfactory ability to discriminate between the smell of water and cycloheximide solution, a strong repellent for rodents. Rats were divided into two groups based on their olfactory discriminative abilities. The olfaction positive (+) group achieved 83% +/- 1% correct responses and the distances of the LOT-transected sites from the middle cerebral artery of this group ranged between 0.8 and 2.4 mm (n = 8). The olfaction negative (-) group achieved 48% +/- 1% correct responses and the distances of the LOT-transected sites from the middle cerebral artery ranged between 2.5 and 4.2 mm (n = 10). From these data, we concluded that the site of the LOT critical for olfactory function is located approximately 2.5 mm from the middle cerebral artery. (c) 2012 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved., Article, NEUROSCIENCE RESEARCH. 73(1):17-23 (2012)

The structural features of calbindin-positive neurons were studied in the mouse main olfactory bulb (MOB). Calbindin-positive neurons were heterogeneous, including numerous periglomerular cells, a few granule cells, small to medium-sized interneurons in the external plexiform layer, and large short-axon cells located in the external plexiform layer, internal plexiform layer, granule cell layer and ependymal/subependymal layer. These large short-axon cells were also heterogeneous; some corresponded to classically identified short-axon cells such as Blanes cells, Golgi cells, horizontal cells and vertical cells, but some others appeared to be previously unidentified. A few faintly calbindin-positive presumed tufted cells were also encountered. Near the ependymal/subependymal layer of the MOB some calbindin-positive short-axon cells extended their dendritic processes more or less parallel to the sagittal plane, presumably corresponding to medullary cells named recently. In addition we encountered a few calbindin-positive horizontal cells in the internal plexiform layer extending their axons toward the lateral olfactory tract, one of which was confirmed to extend its axon into the lateral olfactory tract, indicating that they were presumed to be one of projection neurons. The present study revealed the diversity of calbindin-positive neurons in the mouse MOB and their particular structural properties hitherto unknown.