The Relationship Of The Cognitive Impairment, The TH Levels And Synaptotagmin Ⅰ And Rab3a In Brain Regions In Middle-aged KM Mice

Objective We study the effect of age on the cognitive impairment,the TH levels and the levels of synaptotagminâ… and Rab3a in brain regions in middle-aged KM mice, finally we explore the relationship of the above index.Methods The cognitive impairment was measured respectively in the novel-object recognition task and radial six-arm water maze(RAWM),followed by detection of the levels of total triiodothyronine(TT₃) and total tetraiodothyronine(TT₄).Then western blotting method was used to detect the expression of the protein synaptotagrninâ… (Sytâ… ), Rab3a andβ-actin in the different brain regions.The pictures were dealed with the Photoshop CS software and the Image-Pro Plus 6.0 system.All the dependent variables were entered into STATISTICA for statistical analyses.Resultsâ‘ In the novel-object recognition task,a non-spatial cognitive task,there was no difference between the two groups.â‘¡In the RAWM,a spatial learning and memory task,the performance in the 5-month-old mice was better than that in the older mice. The levels of TT₃ and TT₄ in the 12-month-old mice were decreased compared to the 5-month-old mice.â‘£Compared to the 5-month-old group,12-month-old group had no different in the relative levels of Sytâ… and Rab3a in brain regions.⑤Interestingly,for all mice combined,the TT₄ level was positively correlated with the spatial learning and memory ability in the RAWM,while the TT₄ level only related with spatial memory ability.â‘¥There is no relationship between the TT₃ level and Sytâ… and Rab3a in brain regions.The TT₄ level was correlated with Rab3a in olfactory bulb and ventral hippocampus respectively,but not Sytâ… .In other brain regions there is no relationship between the TT₃ level and the Sytâ… and Rab3a. Conclusionsâ‘ There was spatial cognitive impairment in middle-aged KM mice,but no non-spatial cognitive.â‘¡The levels of TT₃ and TT₄ in the 12-month-old mice were decreased.â‘¢The relative levels of Sytâ… and Rab3a in brain regions were no different between the two groups.â‘£The decreased levels of thyroid hormones in middle-aged mice might be responsible for the impairment of spatial learning and memory.⑤The TH level wasn't prominent correlated with Sytâ… or Rab3a in brain regions.