Effects Of Natural Herb A On Synaptic Transmission And The Underlying Molecular Mechanism In Monocular Deprived Rats

ObjectiveOur interests in this study focused on the influence of development and monocular deprivation(MD)for long-term potentiation(LTP)in rats.The second purpose of this study is to investigate the role of the natural herb A in treatment of adult amblyopia in experimental animal models.MethodsPartⅠ:Fourty eight wistar rats were equally and divided into two groups:①Twenty four wistar rats were divided into four groups:normal controlⅠ(postnatal 45days),normal controlⅡ(P90),MD GroupⅠ(P45),MD groupⅡ(P90).In MD groups,right eyes of each subject rats were sutured.Extracellular recording technique was used to record signals in the layerⅡ/Ⅲof the visual cortex of the anesthetized rats.The synaptic transmission of LTP induction,the variance of EPSP (excitatory postsynaptic potential)slope and PS(the population spike)amplitude after HFS were compared among the four groups.②Twenty four wistar rats were divided into four groups:normal control group(P90),MD control group(P90),low-dose MD group and high-dose MD group(P90).Natural herb A(10,100 nmol·L^-1)were administered via the lateral cerebral ventricle for low-dose group and high-dose group.Normal group and MD control groups were given ACSF(artificial cerebrospinal fluid)as control. Extracellular recording technique was used to record the variance of EPSP slope and PS amplitude after 10,30,60,90min administering natural herb A and ACSF.And then given HFS,the efficiency of drug in LTP induction were compared among the groups.PartⅡ:Twenty four wistar rats were divided into four groups:normal group(P90),MD(P90)group,low-dose group,high-dose group.Low-dose and high-dose group were given Natural herb A(10,100 nmol·L^-1)through lateral cerebral ventricle.One week later after treatment,the expression of nNOSmRNA in visual cortexes by RT-PCR were measured and compared among the four groups.PartⅢ:Grouping and giving the formula type with PartⅡ.One week later after treatment,the expression of NMDA R1 in visual cortexes by immunohistochemistry were compared among the groups.Results1.The influence of development and monocular deprivation on synaptic transmissions in visual cortexes:PartⅠ:①The induction of LTP was highest for normal P45(5/6),the MD P90 group being the lowest.②Comparison of EPSP slope and PS amplitude to basical transmission after HFS(high frequency stimulation):After HFS on layerⅣvisual cortex,with the time lengthens the slope enhances for controlⅠ(P45),normal controlⅡ(P90)(P＜0.01).For each same time,at 30,60min,there were significant difference among the groups(P＜0.01).2.The influence of natural herb A on visual cortical synaptic transmissions in adult MD rats:PartⅠ:①The influence of different concentration natural herb A on basic synaptic transmission:10,30,60 and 90 min after administrating natural herb A,the EPSP slope and the PS amplitude were increased,and there were no difference for control groups after administrating natural herb A.②At 30 and 60 min after the stimulation,EPSP slope and the amplitude of PS in high-dose group and low-dose group were higher than in MD control group(P＜0.01).3.The expression of nNOSmRNA in different groups:PartⅡ:The nNOSmRNA expression in visual cortexes in MD group were lower than normal group(P＜0.01).After given high-dose natural herb A,the expression of nNOSmRNA can be upregulated(P＜0.05).4.The expression of NMDAR1 in different groups:PartⅢ:The NMDAR1 expression in visual cortex in MD group was lower than normal group(P＜0.01).After given high-dose natural herb A,the expression of NMDAR1 can be upregulated(P＜0.05).Conclusions1.The induction of LTP in experimental rats relied on visual experiences,MD can degrade LTP induction.Aging and abnormal visual experience(such as MD)can possibly inhibit HFS-induced reactions in the visual cortexes.2.Natural herb A can enhance the basic synaptic transmission at the levelⅡ/Ⅲ of the visual cortex,which may result in improved LTP induction after HFS,high-dose group was more significant.3.Natural herb A can upregulate the expression of nNOS mRNA and NMDA R1 in visual cortexes.