Objective:To investigate the effects of inhaled low level formaldehyde on learning and memory

the body weight

and the expression of CaMKⅡ in hippocampus of Wistar rats of different ages.Methods:48 Wistar rats including 16 neonatal rats(P3)

16 childhood rats(P14) and 16 adult rats(P60) were divided into control groups and formaldehyde exposure groups randomly according to their age.During 28 consecutive days

the experimental groups were exposed to the gaseous formaldehyde(0.5mg/m3) for 2 h/d.The Morris water maze test was conducted to investigate the spatial learning and memory of the rats.The expressions of CaMKⅡ were assayed by immunohistochemical techniques.Results:The body weight of all the experimental groups were less than that of control groups(P<0.05).In neonatal and childhood rats groups

the escape latency in experimental groups were significantly longer than that of control groups(P<0.05)

while the frequency of stepping over the platform location were significantly less than that of control groups(P<0.05)

and the expression of CaMKⅡ in hippocampus in experimental groups showed a significant decrease compared with control groups(P<0.05).But in adult groups there were no significant difference between experimental groups and the control groups(P>0.05)

except with the body weight.Conclusion:Inhaled formaldehyde has a negative effect on learning and memory of Wistar rats;the developing brain appears far more vulnerable than the mature brain.Changes of CaMKⅡ in hippocampus may be one of the mechanisms of the effects on learning and memory.