Does Puberty Affect the Ultrastructure of the Superior Colliculus in Male Albino Rats?

Background: Puberty is the changes in the period of adolescence. The Superior Colliculus (SC) is located in dorsal midbrain. In mammals, the SC formed of seven layers. These layers are classified into superficial and deep parts. g-ratio is the ratio between the axon diameter and the fiber Identification of the g-ratio is valuable for the functional brain studies. The change in the g-ratio may indicate change in the myelination. Aim of the work: The purpose of this study is to investigate the effect of puberty on the histological structure and ultrastructure of the superior colliculus, and the possible changes in the g-ratio, if present, between prepubertal and post pubertal male rats. Materials and Methods: Twenty male albino rats were divided into pre pubertal and post pubertal rats. Rats of each group were anaesthetized with Ketamine, the superior colliculi were dissected; one used for paraffin sections, the other used for semi thin and ultrathin sections. The diameter of the axons and thickness of myelin, then g-ratio, and synaptic density were measured. Results: The ultrastructural study showed that in post puberal group there is significant reduction in axon diameter and increased myelin thickness which disturbed the g-ratio. The synapses showed significant reduction in the post-pubertal group. Conclusion: The superior colliculus exhibited post-pubertal changes in the axon diameter, myelin thickness and g-ratio which might affect the nerve conduction velocity, and in turn, may affect its function in the visual pathway, and other cognitive functions.