Magnetic resonance imaging (MRI) is a noninvasive measurement that is widely used for diagnoses of the brain. MRI also applied to experimental animals in recent years. MRI can time-dependently detect the morphological changes induced by brain injury on the same animal. Methylmercury (MeHg) is an environmental pollutant, and a potent neurotoxin. Acute toxicity of MeHg induces behavioral impairments, such as Coordinated movement, and morphological alteration of brain on mammals. The purpose of this study is to investigate the acute effect of MeHg administration on the morphological changes in mouse brain using MRI.
Methyl mercury chloride (10 mg mercury / kg body weight) was orally administered to ICR male mice at the age of 8 week, daily for 7 days. Coordinated movement was detected by rotarod test every day. T1-weighted images (T1WI) were obtained before and 2, 4, and 7 days after the MeHg administration with 0.156mm tick slice using the MRmini (1.5T) instrument.
The body weights of the MeHg-treated mice were significantly decreased from the 2nd day of the MeHg administration. Falling latency on the rotarod was significantly decreased from the 3rd day of the MeHg administration. The T1WI showed that the lateral and third ventricles expaneded in a time dependent manner from the 2nd day of the MeHg administration. However no significant difference was observed in fourth ventricle volume between the MeHg treated and control mice.
This study demonstrated that morphological changes in the brain induced by MeHg were detected earlier than the impairment of coordinated movement. Therefore morphological observation by MRI can be a potent method to detect the initial effect of MeHg on the brain.