Research On The Effect And Potential Mechanisms Of Gaseous Formaldehyae Exposure On Cognition Abilities Of Rats With Different Age

PART I EFFECTS OF GASEOUS FORMALDEHYDE EXPOSURE ON SPACIAL LEARING AND MEMORY ABILITIES OF RAT WITH DIFFERENT AGEObjective:To establish the gaseous formaldehyde-inhaling Wistar rats'model in different age and study the effects of formaldehyde inhalation on special learning and memory abilities of rat in different age.Methods:We Choose 36 Wistar rats concluded 12 adult rats (2~3 months), 12 childhood rats (20-day-old) and 12 new-born rats and delivered them into 3 teams according to their age. Each team was delivered into control group and experiment group randomly. In 30 consecutive days, the experiment group was put into a blocking organic glass closet exposed to gaseous formaldehyde concentrated 1 mg/m3 for 2 hours per day. The control one was put into the similar organic glass closet without formaldehyde. The concentration in the closet was monitored.The in-door temperature and humidity were kept stable. Their special abilities were tested by their performance in Morris water maze.We test the platform locating latency and error number of all the rats in the first 5 days,then remove the platform in the sixth day and record the times that rats stepped over the platform.Results:(1)We successfully established the rats'model of gaseous formaldehyde inhalation in different age. The models were more stable and reliable by controlling the experiment conditions.(2)The concentration of the gaseous formaldehyde and the exposure mode had simulated the situation of people exposed to formaldehyde in the room, so the results had more comparability.(3)Platform locating latency (PLL) made by rats in formaldehyde exposure group was longer than that of the control group (p<0.05).The difference of the newborn group was more notable (p<0.01).(4)No significant differences in error number between the control groups and the exposure ones in both adult and childhood groups (p>0.05). Notable difference in error number was seen between the control group and formaldehyde exposure one (p<0.05) in the newborn team. (5)Compared to the control groups, the frequency of formaldehyde exposure groups to step over the platform location decreased notably in the sixth day.Conclusion: Formaldehyde inhalation has adverse effects on special abilities of rats in different age; the newborns were more sensitive to it. PART II RESEARCH ON THE POTENTIAL MECHANISMS OF THE EFFECTS ON COGNITION ABILITIES OF GASEOUS FORMALDEHYDE EXPOSURE OF RATS WITH DIFFERENT AGEObjective: To explore the potential neuron toxic mechanisms of gaseous formaldehyde, by the morphology change and the expression of SYN,BDNF,NPY in the brains of exposed rats in different age.Methods: We Choose 36 Wistar rats with different age concluded 12 adult rats(2~3 months),12 childhood rats(20-day-old)and 12 new-born rats. According their age rats were delivered into control group and formaldehyde exposure group randomly. During 30 consecutive days, the experiment groups were put into a blocking organic glass closet of 1mg/m3 concentrated gaseous formaldehyde for 2 h/d. The completed models were sacrificed to investigate the morphology change of the hippocampus by Nissel-staining and to observe the location of the cell type expression of SYN,BDNF and NPY in the neurons.Results: The Nissel staining showed that Nissel bodies in CA1 pyramidal cells of exposure groups in each age group decreased and vanished in some neuron. Changes were more significant in the childhood group and newborns.The expression of SYN and BDNF protein was remarkably decreased in exposure groups of any age(p<0.05),especially that of the newborn (p<0.01).The expression of NPY protein was remarkably decreased in exposure groups of childhood and newborn group(p<0.05),but there were no significant change in adult group(p>0.05).Conclusion: Gaseous formaldehyde exposure affected the morphology of hippocampus and decreased the expression of SYN,BDNF and NPY in hippocampus and cortex neurons of any age, especially that of the younger. Exposing to gaseous formaldehyde did harm to the cognition abilities of rats in different age especially in the younger.