Effects Of Oxytocin At Different Time Windows On The Expression Of P-ERK And C-fos Protein In Frontal Cortex Of Autism Model Rats

Objective: The aim of this study was to compare the effects of oxytocin at different time windows on ERK phosphorylation and c-Fos protein expression in prefrontal cortex of autism model rats.To explore the dynamic changes of ERK,p-ERK,c-Fos protein expression in prefrontal cortex of autism model rats,and the best medication time of oxytocin to improve social disorder of autism.Methods: According to Schneider’s method of modeling autism model rats,cleangrade wistar rats(a total of 30,20 female rats,and 10 male rats)were selected and caged.At 12.5 days of pregnancy in the experimental group,600 mg/kg VPA(Dissolved in normal saline at 250 g/L),the control group was injected with the same amount of normal saline,and the offsprings were born through growth and development records and behavioral testing and analysis to identify the model.Using the random number table method,the autism model pups were randomly divided into OXT-I group,OXT-II group,VPA-I group,and VPA-II group.Starting from P7 and P21,intranasal infusion of 0.2m L/kg oxytocin(administration dose: 100 μg/kg)for OXT-Ⅰ and OXT-Ⅱ groups for 1week,intervention for the nose of VPA-Ⅰ and VPA-Ⅱ groups drop the same amount of saline for 1 week.The rats in the control group were randomly divided into NS-Ⅰ and NS-Ⅱ.The rats were given the same amount of normal saline for 1 week starting from P7 and P21.All the pups were given sufficient feed and water in the same environment,and the growth and behavior data were observed and recorded.At P7,P14,P21 and P28,3 offspring rats were randomly selected from NS-Ⅰ group,NS-Ⅱ group,VPA-Ⅰ group and VPA-Ⅱ group.At P14 and P28,3 offspring rats were decapitated from OXT-Ⅰ group and OXT-Ⅱ group.The morphology of neurons in prefrontal cortex was detected by HE staining,and the protein expressions of ERK,p-ERK and c-Fos were detected by Western blot.At P28,6 rats were selected from each of the six groups to compare their social ability,repetitive stereotyped behavior and spatial novelty exploration ability.Results:(1)The autism model group had abnormal growth and development,lower body weight and brain weight at four days of age(P7,P14,P21,P28)than the control group,delayed eye opening time,and longer time required for directional orientation test.Compared with the control group,the cumulative time of repeated and stereotypical behaviors increased significantly,the preference for social odor decreased,the social interaction appeared certain degree of disorder,the social novelty ability deficiency,Tmaze test,manifested as fixed path and habit,lack of exploration behavior of new arms.(2)The number of pyramidal cells in the prefrontal cortex in the autism model group was less and there were abnormal neuronal cells.(3)The trend of t-ERK expression in the prefrontal cortex of the autism model group was opposite to that of the control group,which increased at P21～P28(p<0.05),and P7～P14 was lower than the control group(p<0.05);The change trend of p-ERK expression in the autism model group is different from that of the control group,it is higher at P21～P28(p<0.05),P7～P14 is lower than the control group(p<0.05),and there is no significant difference between the control group;The change trend of the p-ERK/t-ERK ratio in the control group and the autism model group is the same as that of p-ERK,the autism model group is higher at P21～P28(p<0.05),P7 is lower than the control group,and P21 is higher than the control group(p<0.05);The expression of c-Fos P7～P21 in the autism model group gradually increased,and its change trend was the same as that of the control group,and P14～P21 was higher than that of the control group(p<0.05).(4)Compared with the VPA group,there was no significant difference in body weight and brain weight in the OXT group,and there was no significant improvement in the spatial novelty exploration ability of stereotypical behavior.OXT-Ⅰgroup improved social communication,social interaction and social novelty to a certain extent,while OXT-Ⅱ group only improved social interaction ability.(5)Compared with the VPA group,the number of pyramidal cells increased in the OXT group,but there were still abnormal nerve cells,and the increase in the number of nerve cells was more obvious in the OXT-Ⅰ group.(6)The expression of t-ERK in the prefrontal cortex of the OXT-Ⅰ group was not significantly different from that of the VPA-Ⅰ group,and the OXT-Ⅱ group was lower than that of the VPA-Ⅱ group(p<0.05);The expression of p-ERK in the prefrontal cortex of OXT-Ⅰ group was higher than that of VPA-Ⅰ group(p<0.05);the ratio of p-ERK/tERK in the prefrontal cortex of OXT group was higher than that of VPA group(p<0.05);there was no significant difference in the expression of c-Fos between OXT group and VPA group.Conclusion: Abnormal morphology and number of prefrontal neurons in VPA autism model rats;the expression of ERK,p-ERK,and c-Fos proteins in the prefrontal lobe is dysregulated,and it shows an upward trend within 7 to 28 days of age;oxytocin improves the level of ERK phosphorylation in the prefrontal lobe of VPA autism model mice and improves their social disorders;comparing the two medication time windows,the application of oxytocin at the age of 7 to 14 days has a better effect on improving the social disorders of VPA autism model rats.