Objective:To investigate the protective effect of ultrasound-combined microbubbles on hippocampal acetylcholinesterase(AchE) fibers in rats.Methods:According to random digits table,60 SD rats were divided into two groups,marrow stromal cells(MSCs) intracranial transplantation group and MSCs intracranial transplantation + ultrasonic microbubbles group.Marrow stromal cells were cultivated and isolated in vitro;12 weeks after transplantation,spatial learning and memorizing abilities of rats were assessed by Morris water maze;AchE staining method was used to observe changes in density and appearance of AchE staining positive fibers in hippocampal CA1 region.Results:There was asignificant increase in spatial learning and memorizing abilities of rats in MSCs intracranial transplantation + ultrasonic microbubbles group.Hippocampal AchE staining suggested an increase in the density of AchE staining positive fibers in MSCs intracranial transplantation group;the fibers were regular,intact and dense.Density of hippocampal AchE positive fibers was negatively correlated with the escape latent period and was positively correlated with percentage of the time needed to cross each platform quadrant.Conclusions:Better promotion of spatial learning and memorizing abilities of rats in MSCs intracranial transplantation + ultrasonic microbubbles group may be related with the protective effect of ultrasound-combined microbubbles on hippocampal acetylcholine fibers. Objective: To investigate the protective effect of ultrasound-combined microbubbles on hippocampal acetylcholinesterase (AchE) fibers in rats. Methods: According to random digits table, 60 SD rats were divided into two groups, marrow stromal cells (MSCs) intracranial transplantation group and MSCs intracranial transplantation + ultrasonic microbubbles group. Marrow stromal cells were cultivated and isolated in vitro; 12 weeks after transplantation, spatial learning and memorizing abilities of rats were assessed by Morris water maze; AchE staining method was used to observe changes in density and appearance of AchE staining positive fibers in hippocampal CA1 region. Results: There was asignificant increase in spatial learning and memorizing abilities of rats in MSCs intracranial transplantation + ultrasonic microbubbles group. Hippocampal AchE staining suggested an increase in the density of AchE staining positive fibers in MSCs intracranial transplantation group ; the fibers were regular, intact and de nse.Density of hippocampal AchE positive fibers was negatively correlated with the escape latent period and was positively correlated with percentage of the time needed to cross each platform quadrant. Conclusions: Better promotion of spatial learning and memorizing abilities of rats in MSCs intracranial transplantation + ultrasonic microbubbles group may be related with the protective effect of ultrasound-combined microbubbles on hippocampal acetylcholine fibers.