Structure of the Main Olfactory Bulb and Immunolocalisation of Brain-Derived Neurotrophic Factor in the Olfactory Layers of the African Grasscutter (Thryonomys swinderianus - Temminck, 1827)

Abstract

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.

Species Specific Structural Differences of the Main Olfactory Bulbs in Dog (Canis Familiaris) and Goat (Capra Hircus)

“…MOBs were obviously seen at ventrolateral and ventral brain views in dog and goat, respectively. These findings are similar to those described in a previously published study [24] that the adult African grass cutter olfactory bulbs were visible on the dorsal brain view but the elephant olfactory bulbs were hidden under the frontal lobes [25].…”

Gross Morphology of the Cerebrum and Brainstem of the Adult African Grasscutter (Thryonomys Swinderianus—Temminck, 1827)

“…Gross morphological studies of the corpora quadrigemina [11], cerebellum [4,15] and olfactory bulbs [14] of the African grasscutter are available in extant literature. Conversely, no detailed account of the cerebrum and brainstem is available and the purpose of this article is to provide descriptive information to fill this gap.…”

Histological Features of Olfactory Bulb Layers in the African Striped Ground ‎Squirrel (Xerus erythropus)‎

“…In the present study, the six layers Cytoarchitecture of the OB in the adult ASGS is in line with the findings of Olude et al (2014) in Africa giant rat (AGR). Conversely, 5 layers were reported in African grass cutter (Ibe et al, 2018) and four (4) layers in African giant rat (Nzalak et al, 2005). Comparatively, previous studies have also revealed up to eight (8) layers in Elephant and other vertebrates (Shoshani et al, 2006;Smitka et al, 2009) to include the ependymal layer and external granular layer.…”