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Introduction: The study described the lamina organization and immunolocalisation of brain-derived neurotrophic factor in the cerebellar cortex of the African grasscutter, at defined postnatal periods. Materials and Method: Brain samples extracted from African grasscutter neonates on postnatal day 3, juveniles on postnatal day 72 and adults on postnatal day 450 were prepared for routine histology and immunohistochemistry, using antibody specific to brain-derived neurotrophic factor. Results: On postnatal day 3, all the laminae typical of the concentric lamina organisation of the mammalian cerebellar cortex were evident, but, and external germinal layer was also observed. On postnatal day 72, and thereafter, the external germinal layer was no more evident. On postnatal day 3, the tree-like arrangement (Arbor vitae) of the cerebellum was not very striking, as the interlobular fissures were incomplete. On postnatal day 72, the Arbor vitae were better presented, as more lobules had been completely separated by interlobular fissures; although, there were some incompletely separated lobules, presented with interlobular fissural lines. On postnatal day 450, the lobules were distinct as the interlobular fissures separated all the vermal and hemispheric lobules. In all the postnatal periods, the granule cell layer was the most populated, while the Purkinje layer was a single cell line of Purkinje neurones. At all postnatal periods, strong immunoreactivity to brain-derived neurotrophic factor was observed in the Purkinje layer; the cell bodies and dendrites of all Purkinje neurones were immunoreactive; while the nuclei in neonate Purkinje neurons where not immunoreactive, the nuclei in the adults were immunoreactive. The cerebellar granule cells were not brain-derived neurotrophic factor immunoreactive, suggestive of their non-synthesis or loss of the synthesized protein, by anterograde axonal transport, to paracrine function. Conclusion: These findings and others were related to some behaviours of the African grasscutter, and compared with similar report in other rodents.

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Key words:African grasscutter, Brain derived neurotrophic factor, Main olfactory bulb, Mitral cells, olfactory glomerulusThe present study has provided some novel findings on the structure of the olfactory bulb in the African grasscutter, by basic neuro-anatomical technique and immunhistochemical technique, using antibody specific to brain-derived neurotrophic factor. Brain samples extracted from neonates on postnatal day 3, juveniles on postnatal day 72 and adults on postnatal day 450 were utilised for the study. There was a consistent increase in the relative weight of the olfactory bulb with advancement in age, but a significant (P < 0.05) decrease in the relative length from 20.81 ± 0.37 on postnatal day 3 to 17.75 ± 0.45 on postnatal day 72. The concentric lamina organization of the olfactory bulb was evident on postnatal day 3, but the glomerular layer was completely absent. The layer was evident on postnatal days 72 and 450. The mean diameters of each glomerulus on postnatal days 72 and 450 were 86.82 ± 0.25 µm and 117.14 ± 0.32 µm, respectively. The difference was significant (P < 0.05). The zones of the external plexiform layer were undifferentiated on postnatal day 3. There was a decrease in the number of mitral cell layer, but increase in size of each mitral cell, with advancement in age. Brain-derived neurotrophic factor was moderately immunolocalised in the olfactory nerve layer on postnatal day 3, but negative on postnatal days 72 and 450. Cell bodies of the periglomerular short-axon neurones mildly expressed brain-derived neurotrophic factor on postnatal days 72 and 450. The granule cells did not express brain-derived neurotrophic factor on all postnatal periods. The functional significance of the results was discussed.

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