Diabetes mellitus type 1 induces dark neuron formation in the dentate gyrus: a study by Gallyas' method and transmission electron microscopy.

BACKGROUND Diabetes mellitus type 1 is a chronic endogenous stressor. We investigated the effects of a diabetes mellitus type 1 on dark neuron formation in granular layer of dentate gyrus. MATERIALS AND METHODS Diabetes was induced by a single intraperitoneal (IP) injection of streptozotocin (STZ) at a dose of 60 mg/kg dissolved in saline. Control animals were received only saline. In the end of eight weeks, the brains were removed and hippocampi studied by Gallyas' method and transmission electron microscopy. RESULTS The comparison between the rate of dark neurons in diabetic group (223 ± 25) and of control (5.75 ± 4.34) showed significant level of difference (p<0.05). Ultrastructurally dark neurons showed apoptotic death criteria namely: dark and electron dense appearance, chromatin condensation, margination and clumping. CONCLUSIONS Present results suggest that STZ-induced diabetes accelerates dark neuron formation with apoptotic criteria in granule layer of dentate gyrus.