Expression levels of brain nicotinic acetylcholine receptor mRNA and protein in coal-burning type of fluorosis rats

Abstract

：Objective To observe thelearning and memory changes in coal-burning type of fluorosis rats, detect the expressionsof neuronal nicotinic acetylcholine receptor(nAChR) at mRNA and protein levels in ratbrains and to reveal the mechanism of changed learning and memory ability. MethodsTwenty-four healthy SD rats, weighting 100 - 120 g, were randomly divided into threegroups(8 in each). Control group was fed with normal diet, and low- and high-dose fluoridegroups were fed with corn polluted with high fluoride (fluoride were 11.30,104.20 mg/kg,respectively) during drying processes with local burning-coal from the areas of endemicfluorosis to established rat model of chronic fluorosis. After exposed to fluoride for 6months, behavioral changes were measured by Morris water maze. Animals were sacrificed,the brain was taken, after homogenizing the fluoride content of brain tissue wasdetermined by fluoride ion selective electrode. The α3, α4 andα7 nAChR subunits at mRNA and protein levels were analyzed by real-time PCR andWestern blotting, respectively. Results For rats in low- and high-fluoride groups, theescape latency time[(12.42 ± 8.03),(17.48 ± 8.05)s] was significantly longer than thatin the control[(7.04 ± 3.29)s, all P 0.05).Furthermore, the protein levels of α3, α4 and α7 nAChR subunits in rat brains ofhighfluoride group(0.58 ± 0.13,0.16 ± 0.03,1.41 ± 0.38) and low-fluoride group(0.56 ±0.23,0.08 ± 0.02,0.51 ± 0.16) were significantly lower than those of controls( 1.48 ±0.42,0.57 ± 0.21,2.56 ± 0.26, P<0.05 or < 0.01). Conclusions Decreased ability oflearning and memory in coal-burning type of fluorosis rats may be associated with declinedexpressions of nAChR at proteins and mRNA levels, which might be the main mechanism of thebehavior change. Key words: Fluoridepoisoning;  Brain;  Nicotinic acetylcholine receptors;  Learning;  Memory