Behavioral response of chicks exposed to manganese by drinking water and mobilization of body manganese burden by EDTA

Abstract

Muna H.I. Al-Zubaidy, Fouad K. Mohammad

Manganese (Mn) is a neurotoxicant in various animal species including the chicks. The present study examines the effect of Mn on the behavioral response of chicks, plasma and tissue Mn levels and the effect of the metal chelating agent disodium EDTA in reducing high levels of the metal in the plasma and some vital organs. Day old chicks were provided with either deionized water (control group) or with Mn at 1 g/L of deionized water as the drinking water for 14 days. On treatment days 7 and 14, all chicks were individually monitored for 3-min open-field activity and then they were subjected to tonic immobility test. On days 7 and 14, the concentrations of Mn in the plasma, whole brain, liver and kidney were determined by atomic absorption spectrometry. Seven or eight day-old chicks were treated intramuscularly (i.m.) with either saline at 5 ml/kg (control), Mn at 20 mg/kg followed 30 min later with saline, or with Mn at 20 mg/kg followed 30 min later with EDTA at 50 mg/kg. The concentrations of Mn in the plasma, whole brain, liver and kidney were determined two hours after the Mn injection by atomic absorption spectrometry. Mn increased the general locomotor activity of the chicks in the open-field arena (lines crossed) and decreased the duration of tonic immobility response of the chicks on treatment day 14 in comparison with the control group. The administration of Mn in the drinking water at 1 g/L increased Mn concentrations in the plasma, whole brain, liver and kidney of the chicks on days 7 and 14 in comparison with the control values. Higher levels of Mn were attained on day 14 compared with those of day 7. Injection of Mn at 20 mg/kg significantly increased the metal concentrations in the plasma, whole brain, liver and kidney of the chicks. The highest concentration of Mn appeared in the kidney followed by the liver, whole brain and the plasma. Injection of EDTA at 50 mg/kg significantly reduced Mn concentrations in the plasma and whole brain when compared with those of the saline-treated group. The data suggest that Mn is well absorbed and distributed into the tissues after exposure of young chicks via the drinking water or i.m. Mn changed the behavioral performance of the chicks and EDTA effectively reduced acute Mn overload in the body. These results further support and expand previous studies concerning the experimental use of young chicks as a potential model of acute Mn neurotoxicity.