Loach (Misgurnus anguillicaudatus) is an essential commercial fish in China. We aimed to give some notes on brain histology of loach fish and characterize the sites
of stem cells in the brain. As well as, we showed the sites of proliferating cells with detection of their glial property. To this end, we histologically observed the
structure of the brain via hematoxylin and eosin stain. We also used fluorescent in situ hybridization to evaluate the localization of Msi1, Bmi1, and Sox2. They are
essential genes expressed in brain stem cells of loach. Proliferating cells were evaluated by PCNA immunofluorescence. As well as GFAP immunofluorescence was
used for detection of the gial property of proliferating cells. Our results indicated that the neural stem cells were located in the granular cell layer of the cerebellum,
vagal lobe, facial lobe, optic tectum, and beside the third ventricle because these sites exhibited expression of Sox2. There were several areas of the brain that
contained proliferating cells, including the cerebrum, in the torus longitudinalis, and in between the optic tectum and cerebellum. In the cerebellum, the proliferating
cells were present in the molecular cell layer, around the intracerebellar ventricle, in the lobus caudalis cerebella, in the eminentia granularis, and around the
rhombencephalic ventricle. Proliferating cells were also observed in the three layers of the vagal lobe and throughout the facial lobe. These proliferating cells were all
negative for GFAP. The present study provides valuable insight into neural stem cells in loach brain, and these findings can be used to guide future studies.