The 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 lines, 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.
Key words: African grasscutter, Brain derived neurotrophic factor, Main olfactory bulb, Mitral cells, Olfactory glomerulus
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