| Objective To detect the expressions of muscarinic acetylcholinereceptors（mAChRs）at mRNA and protein levels in the brain of adult and offspringrats with chronic fluorosis，and to reveal the action of the oxidative stress. Toinvestigate the mechanism of the receptors with brain injury and the ability oflearning and memory reduced. Methods Ninety healthy Sprague Dawley (SD) ratswere divided randomly into three groups (30in each, half male and half female). Inthe control group, the rats were fed with drinking water containing no more than0.5mg/L fluoride; in the fluoride group, the rats were fed with high doses of sodiumfluoride in drinking water (50mg/L) and the VitE antagonitic group with the samecontent of fluoride in drinking as the fluoride group，but adding VitE (50mg/kg) byintragastric administration once a day. All rats were fed with normal diet (＜1mgNaF/kg)，and exposure to fluoride for10months. Choose50pups which were bornwith adult SD rats with every group, each newborn offspring rats were breastfeedingwith the each group females. The feeding conditions were the same as each group ofadult rats after21days, and selected with ages of1,7,14,21and28day in thesenewborn offspring rats. Behavioral changes wre measured by Morris water maze inthe adult and28days of offspring rats and the dental fluorosis of the rats wasexamined. After the animals were sacrificed, taken the brains and measured theweight of brains, while the fluoride content in urine and bone tissues determined byfluoride ion selective electrode. Observed the histological structure and the Nissl’sBody in the nerve cells with Nissl staining in brain of rats under light microscopes.The M1and M3subunits at mRNA and protein levels were detected by real-time PCR,western blotting and immunohistochemistry, while the activities of superoxidedismutase (SOD)and glutathione peroxidase (GSH-Px), the level of malonaldehyde (MDA) and the levels of OH-, H2O2and O2·-in rat serum and/or brain tissues weredetected by biochemical methods. Results In the rats of the fluoride group, the dentalfluorosis with different degrees were observed, the contents in urine and bone tissueswere significantly higher (P＜0.05) and the weight of brains were significantly lowerthan the control(P＜0.05); The escape latency was siginificantly delayed (P＜0.01),the numbers of crossing was decrease platforms (P＜0.01) and the time of staying theplatforms was obviously shortened (P＜0.01)as compared with that control; Under thelight microscope, the neurons in cortex and hippocampal area of the fluorosis ratbrains did not change, but reduced the number of the Nissl’s Body in the neurons andstained shallow(P＜0.05); the protein levels and the mRNA expressions of M1and M3receptors in rat brains were significantly lower as compared to controls(P＜0.05); thelevels of SOD and GSH-px were reduced (P＜0.05) and the content of MDA waselevated of the serum and brains (P＜0.05); while the levels of OH-, H2O2and O2·-were decreased (P＜0.01). Meanwhile, the ability of learning and memory of the28days offspring rats of the fluoride group was significantly lower than the controls (P＜0.05) and the mRNA expressions and protein levels of M1and M3receptors in1,7,14,21and28days of offspring rat brains significantly reduced as compared to controls(P＜0.05). The adult and offspring rats with chronic fluorosis that traeted with the VitEcould obviously reduced these change. Interestingly，the reduced protein levels of M1and M3were positively correlated with the decreased ability of learning and memoryof the rats with fluorosis (r=-0.918,-0.865,0.922,0.938, P＜0.01; r=-0.755,-0.844,0.698,0.777, P＜0.05or P＜0.01). Conclusion The expression levels of mAChRs atmRNA and protein were detected in the brains of adult and offspring rats with excessfluoride, to elevate levels of oxidative stress and reduce levels of antioxidant werefound in brain and serum of the rats, these may be the main mechanism of brain injury.VitE can play an important antagonistic effect in the brain damage induced byfluoride toxicity. |
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