Expression of muscarinic acetylcholine receptors in the brain of rats with chronic fluorosis / 中华地方病学杂志

ABSTRACT

Objective To detect the expression of muscarinic acetylcholine receptors (mAChRs) at mRNA and protein levels in the brain of rats with chronic fluorosis and to reveal the role of the receptors in brain injury and learning and memory deficits.Methods Sixty healthy SD rats were divided into two groups (30 rats in each group,half males and half females) by random number table method according to body weight.In the control group,the rats were fed with drinking water containing no more than 0.5 mg/L fluoride; in the fluoride group,the rats were fed with high doses of sodium fluoride in drinking water (50.0 mg/L).Each group was fed with normal diet (6.2 mg/kg).After being exposed to fluoride for 10 months,behavioral performance was measured with Morris water maze,including the escape latency time and the numbers of crossing platforms.After being sacrificed,rat brains were taken and weighted.M1 and M3 subunits at mRNA and protein levels were detected by real-time PCR and Western blotting,respectively; the correlation between protein levels of the receptor subunits and the ability of learning and memory was analyzed.Results In fluoride group,the escape latency time [(21.68 ± 2.90)s] was significantly longer than that of control group [(6.14 ± 1.71)s,t =0.289,P ＜ 0.05]; and the number of crossing platforms [(11.62 ± 2.26)times] was significantly decreased as compared to that of control group [(19.00 ± 3.69)times,t =0.352,P ＜ 0.05].Furthermore,the mRNA expression [(17.07 ± 6.89)％,(12.25 ± 5.03)％] and the protein levels [(71.07 ± 6.89)％,(32.25 ± 4.66)％] of M1 and M3 receptors in rat brains were significantly lower as compared to those of controls [(100.00 ± 3.00)％,(100.00 ± 2.15)％ and (100.00 ± 9.01)％,(100.00 ± 10.33)％,t =0.210,0.157,0.095,0.296,all P ＜ 0.05].The escape latency and M1,M3 protein levels were negatively correlated (r =-0.683,-0.700,all P ＜0.05),and the number of space exploration and M1,M3 protein levels were positively correlated (r =0.867,0.837,all P ＜ 0.05).Conclusion Declined expression of mAChRs at mRNA and protein levels have been detected in the brain of rats with chronic fluorosis,which may be one of the main mechanism concerning the learning and memory deficits.