Effects of Chronic Administration of Nickel on Memory Function, Hippocampal Neuronal Morphology and Oxidative Stress Factors in Male Adult Rats

Introduction: Nickel (Ni) is a toxic heavy metal that can damage the brain structure, especially the hippocampus which is an important complex brain structure with a major role in memory and learning. Recent studies showed that heavy metals can alter some brain functions and disrupt hemostasis in central nervous system (CNS). The role of chronic Ni administration on memory and leaning, survival of neurons in CA1 hippocampus and the level of oxidative stress marker in rats. Materials and Methods: In total 24 rats (n=6) were allocated to four groups: Group (I): vehicle received intraperitoneal (IP) normal saline (0.9% NaCl), Group (II, III ,IV): received 0.25 mg/kg, 0.5 mg/kg and 1 mg/kg IP NiCl2 for eight weeks, respectively. During this timespan, the rats were examined in the Morris water maze and novel object recognition test to evaluate memory and learning. Finally, the hippocampus of the rats was extracted and survived neurons were evaluated by Nissl staining; oxidative stress was determined using malondialdehyde (MDA) level and catalase enzyme activity. Results: Results showed that dose-dependent Ni administration decreased memory and leaning in behavioral studies and caused degenerative and morphological changes in neurons by elevating MDA and catalase enzyme activity as the most important oxidative stress markers. Conclusion: Ni induces changes in the structure of hippocampal neurons and disrupts memory and learning function in hippocampus in adult rats by an increase in oxidative markers.