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Abstract Summary and Conclusion.The present study is mainly concerned with the study of the postnatal development of the optic nerve “representing the CNS” in diabetic and in control rats. To achieve this objectives diabetes mellitus was induced in neoborn Wistar rat pups by intraperitoneal injection of streptozotocin (STZ) at dose of “90 mg/Kg” for P2 rats. STZ injection produced tri-phasic change in the blood glucose level, first the blood glucose rose rapidly reaching a peak at P12 then rapidly fall down (initial phase of severe hyperglycemia). By the end of third week it returned to a level close to that of age matched controls and remained in normoglycemic state up to the seventh week, (phase of normoglycemia). After that it started to rise again gradually and steadily (phase of mild hyperglycemia.Complete computerized morphometric analysis was then applied to electron microscopic micrographs obtained from different age groups in both control and diabetic rats at different age groups during early and late phase of postnatal development and up to adulthood. It revealed the following results.The optic nerve loses about 50 % This process of elimination seems not affected by diabetic state except during the third week (severe hyperglycemic phase). • The myelinated axons were first detected at P8 in both control and diabetic rats. The number of myelinated axons gradually and significantly increased with age with a maximum rate between 2nd and 4th weeks. The number of myelinated axons was significantly decreased in diabetic animals compared to control in all examined ages. |