Comparative Postnatal Cytoarchitecture of some non-cranial nerve nuclei in the African giant rat (Cricetomys gambianus).

This study postnally compared the cytoarchitecture of inferior olivary nucleus, dorsal and medial nuclei of corpus trapezoidium and; lateral nucleus of reticular formation in African giant rat (AGR). Thirty captive; apparently healthy AGRs consisting ten each of neonates, juveniles and adults were used. Following sedation, euthanasia was achieved by perfusion of 4% paraformaldehyde via left ventricle; head was cut and fixed for three days in 10% formaldehyde before harvesting the brain. Normal histological procedure was performed and tissues stained with Thionin and Haematoxylin-Eosin stains. The following were found: (a) The fibre shaft of inferior olivary nucleus was characterized by radial glial cells in neonates; neurons formed with undivided nucleus in juveniles; three major subnuclei of inferior olive principal, inferior olive dorsal, and inferior olive medial and two minor subnuclei of inferior olive ventrolateral protrusion and inferior olive Beta in adults. (b) The dorsal nucleus of corpus trapezoidium had oligodendrocytes in their nucleus and thick axons in neurons of all age groups. (c) There were numerous immature migrating neurons of radial glial fiber shaft within extracellular matrix of lateral nucleus of reticular formation in neonates, with numerous blood vessels in all age groups. (d) The medial trapezoid body was characterized by numerous giant pyramidal cells in adults. The relatively poor, improved and dominant acoustic structures in neonates, juveniles and adults respectively; with their visual structures generally poorly developed, though better in adults, is an indication that adults have better audition and vision followed by juveniles and lastly neonates.