Histology and Brain Derived Neurotrophic Factor immunoreaction of the neurons in the corpora quadrigemina of the African grasscutter (Thryonomys swinderianus – Temminck, 1827)

The African grasscutter is the second largest rodent in Africa, thus, a key component of the minilivestock industry. The study described the histological features and probed the distribution of Brain Derived Neurotrophic Factor (BDNF) in the corpora quadrigemina of the African grasscutter at foetal and postnatal developmental periods. Brain samples from foetuses explanted on foetal days 60 (F60) and 90 (F90) and extracted from 3 and 6-days-old pups (P3 and P6, respectively), 72-days-old juveniles (P72) and 450-days-old adults (P450) were used. They were prepared for histology and immunohistochemistry. Three laminae were distinct in the rostral colliculi at the foetal and postnatal periods; an outermost stratum zonale, middle stratum griseum superficiale and an inner stratum griseum profundum. Stratum griseum intermediale and stratum medullarium were not distinct. On F60 and F90, the stratum zonale was made of immature neurons, devoid of neurites; the central nucleus of the caudal colliculus was also made of immature migrating neurons. On P3, the neurons were already mature. The stratum zonale was made of medium-sized neuronal cells and thick processes. The thickness of this layer decreased with age. On P3, the caudal colliculus was made of all the components typical of a developed caudal colliculus. There was no BDNF immunoreactive cell in the stratum zonale at any postnatal period; a moderate BDNF-immunoreactivity in the stratum griseum superficiale on P3, a mild immunoreactivity on P6, none reactivity on P72 and mild on P450. The dorsal and lateral cortices of the caudal colliculus were none reactive to BDNF at any postnatal period. The results suggest a better auditory than visual capacity in the rodent.