Abstract: Objective To observe the effect of low level lead exposure during pregnant on the expression of Homer1b/c in hippocampus and the relationship between the exposure and learning and memory in offspring rats.Methods Thirty pregnant rats were randomly divided into 3 groups:a control group fed with doubly distilled water and two treatment groups exposed to 0.05% and 0.2% lead acetate(PbAc) in drinking water during pregnancy and lactation. After weaning, the offspring rats of treatment groups were directly fed with drinking water to postnatal 28 day as their dams.Step-down test was used to observe the change in learning and memory for passive avoidance response at postnatal 56 days.Western blot was used to detect the protein expression of Homer1b/c in hippocampus of offspring rats at postnatal 7, 14, 21, and 28 day, respectively.The contents of lead in blood and hippocampus were determined with atomic absorption spectrophotometer at postnatal 28 days.Results Compared to the controls, the offspring rats exposed to 0.05% and 0.2% PbAc showed significantly longer average escaping latency(39.67±5.18 and 64.82±9.73 vs. 25.71±4.56 seconds) and significantly shorter average remaining latency(147.15±19.26 and 83.56±14.52 vs. 234.89±25.85 seconds) (all P<0.05).The expressions of Homer1b/c in hippocampus of the offspring rats exposed to 0.05% and 0.2% PbAc were 0.607±0.022, 0.825±0.054, 0.583±0.015, and 0.557±0.011and 0.540±0.021, 0.574±0.018, 0.471±0.009, and 0.412±0.007 at postnatal 7, 14, 21, and 28 day, with a decreased tendency compared to those of the control group(P<0.05).Conclusion Chronic lead exposure results in decreases of ability of learning and memory for passive avoidance response in offspring rats and the effect may relate to the decline of homer1b/c expression in hippocampus in rats.