The Effects of Chronic Oral Cobalt Exposure on Passive Avoidance Performance in the Adult Rat

Abstract

Adult rats were tested for step-down passive avoidance following exposure to either water contaminated with CoCl₂ (Group Co) or uncontaminated distilled water (Group X). Behavioral analysis included acquisition and retention performance data and a test for analgesic tolerance. determinations of tissue co levels were also made following termination of the behavioral analyses. Exposure to 20 mg Co/kg body weight/day, for 60 days, produced significantly greater step-down passive avoidance latencies compared to controls during retention testing. Analyses of passive avoidance acquisition data, hot-plate test results and body weights taken just prior to testing produced no group differences. Significant accumulations of Co were found in blood, brain and testes of treated animals. Contrary to previous findings using an equivalent exposure regimen in the food, no testicular atrophy or morphological disruption was found. Behavioral perturbations are discussed in terms of emotionality and possible depletion of gamma-aminobutyric acid reserves in the CNS.