The Effect of Zinc and Melatonin Supplements on Spatial Learning and Memory in Streptozocin-induced Diabetic Rats

Background and Objective: Diabetes mellitus is a complicated metabolic disorder that can impair both spatial learning and memory. The aim of this study was to evaluate the effect of zinc and melatonin supplements on spatial learning and memory in diabetic rats. Materials and Methods: This experimental study was carried out on ۵ groups of male Wistar rats (n=۱۰ for each): the control animals (C) diabetic adult rats with a normal diet (D) diabetic animals receiving ۲۲۷ mg/l zinc in their water (D+Z) diabetic rats receiving ۱۵۰ mg/l melatonin in their water (D+M) and diabetic rats receiving both supplements (D+ZM). Supplementation was started ۵ days before induction of diabetes with streptozocin (۶۰ mg/kg, single dose). Twenty days later, the spatial learning was evaluated by Morris water maze (MWM) for ۵ consecutive days (۴ trials per day). The spatial memory retrieval was estimated on the last day. The serum levels of glucose and insulin were also measured. Results: Diabetic rats spent more time and traveled more distance to find the hidden platform than the controls in the learning stage (P<۰.۰۰۰۱). They also spent less time (P=۰.۰۰۴) and passed a shorter distance in the target quadrant over the probe trial. Supplementation with zinc and melatonin inhibits the spatial learning and memory impairment in diabetic animals. Conclusion: Zinc and melatonin Supplementation seem to reverse the induced impaired spatial learning and memory in diabetic rats.

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Keywords: Diabetes mellitus ، Streptozocin ، Maze learning ، Zinc ، Melatonin ، Rats