Postnatal development of the albino rat superior colliculus

ABSTRACT

The emergence of laminar organization and the developmental changes in cellular and fibrous components of the layers of the superior colliculus of the newborn five, ten, twenty and sixty-day-old-albino rats [Wester Strain] were studied by using three staining techniques; the gallocyanine- chrom alum method for Nissl bodies, nuclei and nucleoli, the Golgi-Cox method for cell bodies and their processes and Holm's method for axons. The superior colliculus of the newborn rat appeared as a large collection of densely packed cells without any evidence of lamination. At the age of five days, a definite pattern of stratification started to appear transforming it into a six-layered structure. At ten days age, there were certain structural changes in the superficial layers of the colliculus, while the intermediate and deep layers showed no additional structural changes except the increase in the layers' thickness. At twenty days age onwards, there were no additional structural changes except the increase in cellular size and laminar thickness in all layers. It was concluded that the intermediate and deep layers of the superior colliculus reached their maturity earlier than the superficial layers. This could be explained as the intermediate and deep layers were involved in connections controlling the adaptive behaviors essential for the still closed-eyes animal, while the superficial layers responsible for controlling visual reflexes and eye movements were delayed in maturation till the animal's eyes start to open