Objective: To observe the influence of coal burning fluorosis on learning and memory ability in rats and reveal its possible mechanisms. Methods: Healthy 48 SD rats were divided into control, low-fluoride and high-fluoride group. All rats in fluoride exposed groups were fed with the com polluted by drying processes with burning coal containing high level of fluoride obtained from the endemic fluorosis area to produce the animal model of fluorosis. The experiment period were 3,6 mouths, respectively. The ability of leaning and memory was measured by Morris test and cholinesterase activity detected by photometric method at 3 or 6 month after experiment, respectively. Results: Fluoride contents significantlly influenced the escape latency, the numbers of crossing the platforms and the time of staying the platforms(the value of F was 29.29,6.47,6.50, respectively, P < 0.01). In addition, the numbers of crossing the platforms and the time of staying the platforms were influenced by the exposed time(the value of F was 16.11,45.59, P < 0.01). Furthermore, the fluoride contents and the exposed time had an interaction between the numbers of crossing the platforms and the time of staying the platforms (the value of F was 4.67,5.68, P < 0.05 or < 0.01). Three months after the experiment, the mean values of escape latency [(14.71 ± 4.85)s] of rats in highly fluoride exposed group were significantly prolonged as compared with controls [(9.28 ± 4.22)s]; 6 month after the experiment, the mean values of escape latency[(12.42 ± 8.03)s, (17.48 ± 8.05)s] of rats in both groups exposed to fluoride were significantly prolonged as compared to controls [(7.04 ± 3.29)s, P < 0.05]. The decreased numbers of crossing the platforms[(1.62 ± 0.87)number] and the declined time of staying the platforms[(16.70 ± 5.02)s] were found in the rats exposed to high fluoride as compared to controls [(3.53 ± 1.67)number, (23.33 ± 5.35)s, P < 0.05]. The fluoride contents obviously influenced the activities of acetylcholinesterase and butylcolinesterase(the value of F was 12.83,13.27, P < 0.01). On the other hand, the times of breeding also influnced the activities of butylcolinesterase(the value of F was 16.26, P < 0.01). In 3 months of the experiment, the activities of butylcolinesterase [(0.55 ± 0.12)kU/g] in low fluoride exposed group were significantly decreased in comparison with controls[(0.73 ± 0.10)kU/g, P < 0.05]. The activities of acetylcholinesterase[(0.62 ± 0.42)kU/g] and butylcolinesterase[(0.58 ± 0.10)kU/g] in high fluoride group were significantly decreased as compared to controls [(1.41 ± 0.52), (0.73 ± 0.10)kU/g, P < 0.05]. The correlation analysis showed that there was a negative correlation between the cholinesterase and the escape latency (r = - 0.68, P < 0.01), and a positive correlation between the cholinesterase and the time of staying the platforms (r = 0.57, P< 0.01). Conclusions: The ability of learning and memory in rats with coal buring fluorosis was decreased, which might be connected to the decreased activity of cholinesterase in a dose-effect correlation.

SD rats (6 Months)

HAWC