Investigations Of The Effects Of Cigarette Smoking Exposure On The Spatial Learning Ability And Neurogenesis Of Mice

To investigate the effects of cigarette smoking exposure(CSE)on the developing central nerve system and its function,we focused on the effects of CSE on adolescent mice's ability of learning and memory,neurogenesis and the population of activated microglia.Being the first report,we find that CSE inhibited hippocampal neurogenesis and decreased the population of activated microglia,proved that neurogenesis has a critical function in learning and memory.Illuminated that CSE effected learning and memory through prohibiting neurogenesis,provided experimental evidences which can demonstrate the impairment of CSE to neurogenesis of adolescent.Our study including two experiments:Part one:The Effects of CSE on Neurogenesis,the Ability of Learning & Memory, and the Population of Activated Microglia of Adolescent Mice【object】To investigate the effect of CSE on neurogenesis,the ability of learning and memory,and the population of activated microglia.【methods and materials】30 days postnatal mice fed under the SPF(specified-pathogens free) standarded envirment were chosed,the differences of physical ability and spatial learning ability between animals were filtered by rota-rob test and square water maze,then were divided into three groups,12 animals per group.The two treated groups were put into the Plexiglas-made box followed Younoszai's design to receive CSE for 8 days.During these days,the group of low intensity CSE were treated three times per day,and one cigarette was lit in ten minutes every time;the group of high intensity CSE were treated three times per day, two cigarettes were lit in thirty minutes per time.Meanwhile,the control was put into the same box without cigarette smoking three times per day,thirty minutes per time for 8 days.We evaluated their spatial learning ability by means of Morris Water Maze test,using the method of immunohistochemistry with 5-bromodeoxyuridine(BrdU)we labeled newly born cells,with Bandeirae Simplicifolia Isolectin-B4(BSI-B4)by the method of affiliate histochemistry we labeled microglia.【results】The animals of CSE treated groups spent visibly more time before they find the hidden plate;the amount of BrdU+ cells in DG were decreased significantly, the quantity of BSI-B4~+ cells diminished strikingly,especially the quantity of cladodromous shaped BSI-B4~+ cells.【conclusion】1.CSE impaired the spatial learning ability of adolescent mice.2.CSE prohibited the neurogenesis and the population of microglia,especially the activated population,in DG.3.There is positive relationship between the capability of learning and memory, neurogenesis,and the population of activated microglia,and some kind of interactions between them are implied. Part two:Study on the Effects of Neurogenesis on Learning and Memory【object】To investigate the effects of neurogenesis on learning and memory,probe into the functions by which CSE impaired the ability of learning and memory.【methods and materiais】By means of microinjection through the tube implanted into lateral cerebral ventricle,we put acid fibroblast growth factor(aFGF),the accelerator of cytodieresis,and methotrexate(MTX)-the inhibitor of cytodieresis into the mice's brain.By the same means of neurobehavior test and cell label,we evaluated their spatial learning ability,neurogenesis and the population of activated microglia.【results】Escape latency of animals treated with aFGF shortened significantly,and the amount of both BrdU~+ and BSI-B4~+ cells enhanced too;on the contrary,the animals were treated with MTX performed markedly worse than the other two groups,the quantity of BrdU~+ cells,but the amount of BSI-B4~+ cells dose not changed visibly.【conclusion】1.aFGF can enhance the neurogenesis and promote the activation of microglia.2.MTX can inhibit neurogenesis,yet have no notable influence on microglia.3.Proved that neurogenesis plays some kind of important role in the procedure of learning and memory from the two different ways by using accelerator and inhibitor of cytodieresis.【summary】1.CSE impaired the spatial learning and memory of adolescent mice.2.CSE repressed the neurogenesis in DG and decreased the population of microglia(especially the activated ones).3.The inhibition in neurogenesis of CSE quite possibly to be the critical function CSE impaired spatial learning ability of adolescent mice.4.Neurogenesis plays an important role in the procedure of spatial learning and memory.5.It is quit possible that there is some kind of interactions among the capability of learning and memory,neurogenesis and microglia.6.aFGF can enhance the neurogenesis while MTX can restrained it.