Effects in memory and learning in rats exposed to arsenic


Introduction: Arsenic (As) is a metalloid that has been found as a natural contaminant in water and by anthropogenic activities, the international standard sets a maximum limit in water of 0.010 mg/l. In Mexico, the Mexican Official Standard NOM-127 SSA January 1994 establishes a maximum allowable limit of 0.025 mg/l; although, it should be mentioned that in some towns of La Laguna, in Coahuila and Durango, Mexico, As concentrations exceed this limit. Different researches have shown health effects by chronic exposures to As, where mostly anthropogenic activities contribute to As levels in water. Only few studies about the effect of As on the memory and medium and long term learning have been developed. Therefore, an experimental model of exposure in rats to evaluate the effects on cognition tied to this contaminant is suggested. Objective: To evaluate the effect of the toxicity of As in memory and learning in Long Evans rats, developing a model of exposure to different concentrations of the metalloid. Materials and methods: Three groups of three rats each were used and exposed to the following concentrations of As, 0.025 mg/L, 0.050 mg/L, and 0.070 mg/L in 50 ml of purified water for four weeks in a five consecutive days of exposure and two days of rest protocol. Animals were subjected to the Morris Water Maze before and after (test–retest) the metalloid exposure. After applying
the Morris Water Maze shaped retest, animals were sacrificed by cervical dislocation. Then the brain was removed and inclusions were made with paraffin and then cuts in the frontal lobe, temporal lobe and hippocampus were done for histopathology analyses. Results: After applying the Morris Water Maze test for the second time (retest), the average of the control group (2.47) was lower than the group average DOS (3.25). With respect to the calculation of the Kaplan–Meier, both the survival function and the hazard function of understanding increased with increasing dose. Conclusions: Based on our results, we can conclude that there is a deterioration in the memory by the exposure to As. Histological analyses are in progress to complete the analysis.

2016 Effects in memory and learning in rats exposed to arsenic