| background and purpose:Autism Spectrum Disorder（ASD）is a severe and widespread neurodevelopmental disorder characterized by disorders in social interaction and communication,rigid behavior,and often accompanied by intellectual development disorders and emotional abnormalities.The exercise rehabilitation training in childhood can improve the abnormal behaviors of ASD patients,such as language,communication,perception and movement.It was found that synaptic plasticity changes occurred in several brain regions of ASD patients,which may be closely related to BDNF-Trk B-Cdc42 signaling pathway.Exercise can ameliorate abnormal behavior of ASD.However,few reports have been reported on specific trends of synaptic morphology and ultrastructure in different brain regions induced by ASD,and the molecular mechanism of how exercise affects synaptic remodeling in different brain regions is far from clear.In this paper,we constructed ASD model rats,and observed the effects of caudate putamen of Striatum（CPu）,nucleus accumbens（NAc）,hippocampus（Hip）,basolateral amygdala（BLA）and other related brain region synaptic density and morphology are analyzed to explore the influence of exercise on synaptic remodeling in different brain regions and related molecular signaling pathways in ASD model rats.Methods :First,ASD model mice were constructed: SD pregnant mice were intraperitoneally injected with valproic acid（VPA）at 10 and 12 days of gestation,respectively.The male offspring were identified as ASD model mice,and the offspring of normal SD pregnant mice（injected with equal volume of normal saline）were used as the control group.The body weight and eye opening of experimental rats on day 1,7,14,28,42 and 56 after birth were observed and recorded.Male normal rats and ASD model rats at day 28 were randomly divided into control quiet group（NS）,control exercise group（NSE）,ASD quiet group（ASD）and ASD exercise group（ASDE）.Thermal pain threshold and behavioral tests were performed to evaluate the effect of ASD model rats.The NSE and ASDE groups received 1 week of adaptive wheel treadmill running and swimming training,followed by 4 weeks of formal running and swimming training,5 days of exercise training per week,and 2 days of rest.The NS and ASD groups received no intervention.Behavior test was performed immediately after exercise training,and then brain perfusion was performed.Tissue blocks of CPu,NAc,Hip and BLA brain regions were isolated according to the brain map of rats.The synaptic density and morphology were observed by transmission electron microscopy,and the expression levels of BDNF,Trk B and Cdc42 proteins in corresponding brain regions were detected by Western blot.Results: 1.Basic physiological indicators: there were no significant differences in body weight and eye opening between ASD offspring and control offspring（P >0.05）,and pain threshold of ASD offspring was significantly higher than that of control offspring（P < 0.05）.2.Behavioral function evaluation: Social interest of ASD rats was significantly lower than that of control rats（P < 0.01）.The self-grooming time of ASD offspring was longer than that of control offspring（P < 0.05）,and they were more prone to stereotyped behavior.New object recognition showed that the ASD offspring were significantly less interested in exploring new objects than the control offspring（P <0.05）.Y-maze test showed that there was no significant difference in the time and times of entering the new heteroarm between the control group and the ASD model group（P > 0.05）.After exercise training,the social interest of ASDE group was significantly higher than that of ASD group（P < 0.01）.The repetitive,rigid and anxiety-like behaviors were significantly reduced in ASDE group（P < 0.05）.New object recognition showed that rats in ASDE group were more interested in exploring new objects than rats in ASD group（P < 0.05）.3.Synaptic ultrastructure: Transmission electron microscopy showed that the synaptic density in CPu region of ASD group was higher than that of NS group（P <0.05）,but showed a decreasing trend in ASDE group but no statistical significance（ASDE vs.ASD）.The synaptic density of NAc and BLA region in ASD group was lower than that in NS group（P < 0.05）,but significantly increased in ASDE group（P< 0.01）.There was no significant difference in the synaptic density in Hip region.Synapse typing showed that the frown type synapse in the CPu region was significantly higher in the ASD group than in the NS group（P < 0.001）,but significantly lower in the ASDE group（P < 0.01）.NAc smile and flat synapse in ASD group were significantly lower than those in NS group（P < 0.001）,while ASDE group were significantly higher（P < 0.01）.In the Hip region,ASD group had significantly fewer smile type synapses than NS group（P < 0.01）,while frown type synapses were significantly more than NS group（P < 0.001）.The smile-type synapse in BLA region was significantly lower in ASD group than in NS group（P < 0.01）,but significantly higher in ASDE group（P < 0.001）.4.Protein expression of BDNF,Trk B and Cdc42: Western blot results showed that the protein expression levels of BDNF（P < 0.05）and Cdc42（P < 0.01）in CPu brain region were significantly increased in ASD group compared with NS group,while the protein expression level of Trk B was increased in ASD group,but there was no significant difference（P > 0.05）.After exercise intervention,the protein expression levels of BDNF,Trk B and Cdc42 in ASDE group were significantly decreased compared with that in ASD group（P < 0.05）.In BLA region,the expression level of BDNF protein in ASD group was significantly lower than that in NS group（P < 0.001）,the expression level of Trk B protein in ASD group was significantly higher than that in NS group（P < 0.01）,and the expression level of Cdc42 protein in ASD group had a downward trend compared with that in NS group,but there was no statistical difference（P > 0.05）.After exercise intervention,compared with the ASD group,the expression of BDNF protein was significantly increased（P < 0.001）,Trk B protein was significantly decreased（P < 0.01）,and Cdc42 protein was significantly increased（P < 0.05）in the ASDE group.The protein expression of BDNF in NAc region of ASD rats was significantly decreased compared with that of NS group（P < 0.05）,while the protein expression of Trk B and Cdc42 in ASD group showed a downward trend compared with that of NS group,but there was no statistical difference（P > 0.05）.After exercise intervention,the expression of BDNF protein in ASDE group was significantly higher than that in ASD group（P < 0.01）,the expression of Trk B protein in ASDE group was significantly higher than that in ASD group（P < 0.05）,and the expression of Cdc42 protein in ASDE group was significantly higher than that in ASD group（P < 0.001）.Conclusion:1.The number and morphology of synapses in Cpu,Hip,BLA and NAc regions of ASD rats were different from that of normal rats.Exercise training could make the synaptic density of brain regions of ASD rats tend to be normal,and the morphology of ASD rats was remodeled.2.The expression of BDNF,Trk B and Cdc42 in different brain regions of ASD rats was different from that of normal rats.Exercise intervention could regulate the expression of BDNF-Trk B-Cdc42 signaling pathway related protein molecules in different brain regions of ASD rats,and such changes were synchronized with the synaptic density and morphology in each brain region. |
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