The Role Of BDNF-TrKB Signaling In The Effect Of RTMS In The Improvement Of Prenatal Stress-induced Cognitive Deficits In Male Offspring

It is very sensitive to external stimulation during the period of pregnancy for female.Clinical studies showed that prenatal exposure to maternal stress was associated with the abnormal development,dysfunction of central nervous system,and cognitive deficits of children.The negative effects of prenatal stress(PNS)are through decreasing glutamate transmission,reducing synapogenesis and BDNF-Trk B signaling.Repetitive transcranial magnetic stimulation(r TMS)is a non-invasive neurological technique,by which a regular magnetic field is produced to induce a secondary current in the brain and then affect attention,memory,and other brain functions.Furthermore,r TMS has been widely employed as an effective therapeutic approach in the clinical such as depression and the basic neuroscience research.Previous studies showed that the spatial learning and memory was improved by r TMS,which was associated with the level of brain derived neurotrophic factor(BDNF)in normal rats.However,it is still unclear about whether r TMS is able to improve the prenatal stress-induced cognitive deficits through BDNF-Tr KB signaling.The aim of the study was to investigate the effect of r TMS on spatial cognition and synapse plasticity for offspring and explore the role of BDNF-Tr KB signaling in this process.This was done by establishing a rat model of prenatal stress.The methods are as follows: 30 d male Wistar rats were randomly divided into 5 groups,which were control group(CON,n=6),prenatal stress group(PNS,n=6),prenatal stress+r TMS group(PNS+r TMS,n=6),prenatal stress+r TMS+DMSO group(PNS+r TMS+DMSO,n=6),prenatal stress+r TMS+K252a(PNS+r TMS+K252a,n=6).From the day 15 to 21 of gestation,prenatal rats in the PNS group were restrained for 3 times daily,45 min each time at random interval.Then the male pups were testing until postnatal 35 day.One session of r TMS was applied daily for 14 consecutive days.Every session consisted of total 400 stimuli.The intensity of stimulation represented 120% of the average resting motor threshold.The CON group and the PNS group were handled ina manner similar to that in the r TMS group,while the coil was lifted to 80 mm above the rat’s head.Rats in the PNS+r TMS+DMSO and PNS+r TMS+K252a group were intracerebroventricularly(i.c.v.)infused with DMSO(1 μl)and K252a(2 m M,1 μl).The Morris water maze test was performed to measure the spatial cognition successively 7 days after the operation.Then,the long term potentiation(LTP)and depotentiation(DEP)from Schaffer to CA1 in the hippocampus were recorded.Western blot assay was used to measure the expression of BDNF,Tr KB,p-CREB/ CREB in the hippocampus.The m RNA and protein level were detect in synaptic-related proteins(SYP,NR2 A and NR2B)by RT-PCR assay and Western blot assay.HE staining was applied to assess the structure and number of pyramidal neurons in the hippocampal CA1 region at the same time.The main results are as follows: In Morris water maze test,it showed that the escape latency was statistically decreased in the r TMS group compared to that in the PNS group at the IT stage,and the target quadrant dwell time and numbers of crossing platform were increased in the SET stage.After treatment with K252 a,the changes were disappeared.In the reversal training(RT)stage,r TMS reduced the escape latency compared to the prenatal stress offspring,and increased the target quadrant dwell time in reversal exploring test(RET).However,after treatment with K252 a,the changes were not disappeared.In vivo electrophysiological experiments showed that the LTP was reduced in the PNS group and the DEP was significantly increased compared with that in the CON group.r TMS increased the level of LTP and decreased the DEP dramatically.However,the LTP was decreased after treatment with K252 a,but there was no difference of DEP between these two groups.The expression level of BDNF,Tr KB,p-CREB/CREB,NR2 A and NR2 B in the hippocampus was significantly decreased in the PNS group compared to that in the CON group.However,it was significantly increased in the PNS+r TMS group compared to that in the PNS group.After treating with K252 a,the expression level of them was considerably reduced.However,there was no difference of SYP expressionlevel among all the groups.The similar results were obtained form the measurement of the m RNA level of SYP,NR2 A and NR2 B in RT-PCR assay.HE staining showed that the number of pyramidal neurons in the hippocampal CA1 regions was decreased in the PNS group compared to that in the CON group,but r TMS significantly increased the number of pyramidal neurons.After treating with K252 a,the number of pyramidal neurons was decreased dramatically.The main conclusions are as follows: r TMS can improve the prenatal stress-induced cognitive and synaptic plasticity deficits in male offspring rats.r TMS is able to promote BDNF-Tr KB signaling,enhance the NR2 A and NR2 B m RNA and protein level and increase the number of pyramidal neurons.