The effect of lead, restraint stress or their co-exposure on the movement disorders incidence in male mice

Lead is known as an environmental contaminant with neurotoxic properties. In addition, people experience different types of chronic stress, especially in developing countries. It has been established that lead or stress causes structural and physiological damages to the neural pathway like dopaminergic connections. Nevertheless, the effect of lead and restraint stress on movement behaviors when are experienced together has not been studied yet. In this study, male albino mice were randomly divided into different groups (n = 6). Lead acetate was daily injected at 15 mg/kg intraperitoneally for 2, 4, or 6 weeks. Restraint stress (6 h in a day) was applied alone or in combination with lead acetate for 2, 4, or 6 weeks. The catalepsy, akinesia, and the balance of animals were measured by bar test, elevated beam device, and rotarod to evaluate the movement disorders. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a known neurotoxin causes movement disorders, was used as positive control group. The results showed that exposure to the lead or stress or their combination for 6 weeks caused catalepsy, akinesia, and imbalance in the animals, while exposure for 2 or 4 weeks didn’t affect the movement items indices. The combination of lead and stress did not show any significant difference compared to the exposure to each of them individually. From the findings, Lead, stress, and their combination caused movement disorders in a time dependent manner. Short time exposure did not change movement behavior. The co-exposure to the lead and stress did not show additive or synergistic effects.