Brain Morphology and Microscopic Studies on the Striato-Pallidal Nuclei of an African Rodent Species; Thryonomys swinderianus (African Grass Cutter)

Thryonomys swinderianus (African grasscutter, AGC) is a breeding species widely spread across Sub-Sahara Africa and recently reported as potential model in neuroscience researches. Striato-pallidal (caudate-putamen, CPu, and globus pallidus, GP) nuclei are subcortical structures that play critical roles including planned voluntary movements in mammals. Hence, elucidating certain regions of AGC brain is critical in understanding the neurobiology of the species. This study described the brain morphologic features and characterized striato-pallidal microscopic features of AGCs. Four AGCs were obtained from a farm in Zaria. AGCs were euthanized, fixed-perfused and the brains harvested for morphologic (brain features and dimensions) and microscopic examination (histological features using H&E stains, and Nissl substances using Cresyl fast violet stain) of striatopallidal regions. CPu was characterized into six-defined quadrants, and histometric features of the fascicules were analyzed. AGC brains were milky in color with sulcal depressions. AGC mean brain weight was greater than 11g and brain length (rostro-caudal) greater than 45mm. Microscopically, section through the cerebrum revealed a subcortical striatum with distinct CPu and GP. These nuclei revealed varying neuronal cells types and glial cells. CPu demonstrated pockets of white mater patches (fasciculi), with varying sizes and abundance across the quadrants. Histometric analysis of fasciculi within the characterized six quadrants showed difference (p<0.05) between quadrants, with higher values on the medial compartments when compared with lateral compartments of CPu. The brain morphologic and striato-pallidal microscopic features of the AGC is typical for a rodent species. These findings present AGC as a potential model in neuroscience related investigations.

Key Words: Brain dimension, Caudate-putamen, Globus pallidus, Histology, White-mater patches.