Improvement of Core Behavior in Autism Spectrum Disorder Mice by 8-Week Aerobic Exercise

Objective To investigate the effect of 8-week aerobic exercise on the improvement of core behaviors of male and female autistic mice induced by valproic acid (VPA). Methods Experimental mice were randomly divided into the control group (CTL), VPA-induced autism group (VPA) and VPA+aerobic exercise group (VEX), with 10 mice in each group. The pregnant mice were injected with VPA intraperitoneally at E12.5, and their offspring were used as autistic mice. Pups were weaned 28 d after birth and began an 8-week aerobic exercise intervention. The day after exercise, mice were tested in behavioral experiments to detect exploratory behavior, social skills, repetitive stereotypic behavior, cognitive ability and mood. The mice were tested for social skills, repetitive stereotyped behaviors, cognitive and learning memory abilities, exploratory behaviors, and emotions by behavioral assays on the following day after the exercise. Results Both male and female mice in the CTL group showed a significant decrease in the total distance and percentage of time spent in the interaction zone in the 4th socialization compared to the 1st socialization (P<0.01); the total distance and percentage of time spent in the interaction zone in the 5th socialization was significantly increased compared to the 4th socialization (P<0.01); in VPA group, both male and female mice showed no significant change in the total distance and percentage of time spent in the interaction zone in the 4th and 5th socialization; in the VEX group, the total distance and percentage of time spent in the interaction zone by male mice in the 4th socialization was significantly decreased compared to the 1st socialization (P<0.01, P<0.05); and in the VEX group the total distance and percentage of time spent in the social interaction zone by both male and female mice in the 5th socialization was significantly increased compared to the 4th socialization (P<0.01, P<0.05). The results of the first phase of three-box socialization experiment showed that male and female mice in the CTL group spent more time socializing with their social partners than in contact with the empty cages (P<0.01); there was no difference in the time spent by male and female mice in the VPA group in socializing with their social partners and the empty cages; and male and female mice in the VEX group spent a longer time socializing with their social partners (P<0.01). The results of the second phase of three-box test showed that male and female mice in the CTL group showed a significant tendency to socialize with new social partners (P<0.01), whereas no significant changes were observed in the mice of VPA group; aerobic exercise significantly ameliorated this deficit in male and female mice with autism. Compared with the CTL group, VPA-induced significant decreases were observed in the total distance freely moved in the central area of the open field, the time and percentage of time spent in the open arm of cross maze, and the distance and time spent in the white box in both male and female autistic mice (P<0.01); a significant increase in the number of bead burials and time spent in self-grooming (P<0.01); a significant decrease in the cognitive index (P<0.01); a significantly longer latency to find the platform, and significantly decreased the percentage of time spent in the target quadrant and the number of times they traversed the platform (P<0.01). Compared with the VPA group, after 8 weeks of aerobic intervention, male and female mice in the VEX group showed a significant increase in total distance, open-arm dwell time, and percentage of free movement in the central area of the empty field (P<0. 05), and a trend toward a decrease in the dwell time of females in the white box was not significant, the number of beads burying and the time of self-combing were significantly lower (P<0.01, P<0.05); and a significant increase in cognitive index (P<0.05), a significantly shorter time to find the platform, and significantly increased percentage of time spent in the target quadrant and the number of times they traversed the platform (P<0.01), showing excellent learning memory. Conclusion Autistic mice severely suffer from social and cognitive impairments, repetitive stereotyped behaviors, decreased activity level, and the exhibition of anxiety. 8 weeks of aerobic exercise can improve the social and cognitive abilities, alleviate the stereotyped repetitive behaviors, increase the activity level, and positively regulate the anxiety in autistic mice. It is hypothesized that aerobic exercise has an important role in motor rehabilitation of autism, in order to provide a theoretical basis for clinical research.