Age Effects On Levels Of Synaptotagmin â…  And â…£ In Dorsal Hippocampus Of Mice And Impact Of Maternal Exposure To Lipopolysaccharide During Late Pregnancy On Them

Background With the world-wide increase of aging population, age-relateded learningor memory decline as well as the senile dementia has become a serious social problem.Alzheimer disease (AD) is one of the most important senile dementia prevalent amongaging people, whose incidence rate grows with age increase. However, the underlyingmechanism leading to the disease and resulted cognitive decline is still incompletelyclear. Since aging is an essentially risk factor for senile dementia, it is extremely valuableto study the mechanisms of age-related decline in learning and memory for understandingthe development and pathogenesis of senile dementia. Recent studies show that thechanges of synaptic protein in specific brain will result in age-related cognitive declineand two kind of synaptic proteins: synaptotagmin (Syt) I and IV are thought to be closelyrelated to hippocampus-dependent learning and memory. However, their effects on thenormal aging process and interventional aging model are still open questions.Objective①To explore the effects of aging on the contents of Syt I and IV in dorsalhippocampus of senescence-accelerated prone mouse (SAMP)8.②To explore thecontents of Syt I and IV in dorsal hippocampus of the middle-aged CD-1mice(accelerated aging in behavioral cognition already emerged), whose mothers had beenintraperitoneally injected by lipopolysaccharide (LPS) during late pregnancy.Methods Three groups of SAMP8mice with different age (old group:13months;middle group:9months; young group;4.5months) and two groups of CD-1middle-agedmice (13months, whose mothers were intraperitoneally injected by LPS and normalsaline respectively during late gestation) were selected, which had already taken related behavioral testing. The contents of Syt I and IV in each subfield of dorsal hippocampuswere detected through immunohistochemical method.Results①Among all different-aged SAMP8mice and middle-aged CD-1mice, theexpressions of Syt I and IV were detected in CA1and dentate gyrus subfields of dorsalhippocampus.②For the SAMP8mice, the relative Syt I content in the13-month-oldmice was significantly higher than that in the9-month-old and4.5-month-old mice ineach stratun of CA1subfields, stratum granulosum as well as molecula of dentate gyrus ofdorsal hippocampus (Ps <0.05), while there were no obvious differneces in the stratumhilus of dentate gyrus between mice in different ages (Ps>0.05).③For the SAMP8mice,the relative Syt IV content in the13-month-old mice was significantly higher than that inthe9-month-old and4.5-month-old mice in each stratun of dentate gyrus and CA1subfields of the dorsal hippocampus (Ps <0.05), except in the pyramidale layer of CA1subfields in which no significant differences were measured between mice in differentages (Ps>0.05).④Compared with the saline-treated group, the relative Syt I content inthe lipopolysaccharide-treated group was significantly higher in each stratun of dentategyrus and CA1subfields of the dorsal hippocampus (Ps <0.05), except in the stratummolecula of CA1subfields.⑤Compared with the control group, the LPS-treated grouphad a significantly increase in Syt IV in each stratun of CA1and the stratum molecula ofdentate gyrus (Ps <0.05).Conclusion①For SAMP8mice, the content of age-related Syt I to different extent,were increased in each subfield of dorsal hippocampus.②Syt IV protein were expressedincreasingly with aging in each subfield of dorsal hippocampus in SAMP8mice.③Formiddle-age CD-1mice whose mother exposure to LPS in late gestation, the contents ofSyt I and IV in each subfield of dorsal hippocampus increased.