Treadmill exercise during pregnancy ameliorates post-traumatic stress disorder-induced anxiety-like responses in maternal rats

Post-traumatic stress disorder (PTSD) is an anxiety disorder triggered by life-threatening events that cause intense fear. Exercise is known to have protective effects on neuropsychiatric diseases. The present study investigated whether treadmill exercise during pregnancy reduced or alleviated symptoms of PTSD in maternal rats. To induce predator stress in pregnant rats, rats were exposed to a hunting dog in an enclosed room. Exposure time was three 10-min daily sessions separated by 1 h, starting at week 1 of pregnancy until delivery. Pregnant rats in the exercise group were forced to run on a treadmill for 30 min once a day, starting one week following pregnancy until delivery. Rats receiving predator stress during pregnancy exhibited PTSD anxiety-like behaviors following delivery. Expression of 5-hydroxytryptamine (5-HT) and its synthesizing enzyme tryptophan hydroxylase (TPH) in the dorsal raphe was increased compared with unstressed rats. Expression of c-Fos and neuronal nitric oxide synthases (nNOS) in the hypothalamus and locus coeruleus were higher in the rats receiving stress during pregnancy compared with unstressed rats. By contrast, treadmill exercise during pregnancy ameliorated anxiety-like behaviors and reduced the expression of 5-HT, TPH, c-Fos and nNOS in the PTSD maternal rats. The results of the present study indicate that exercise during pregnancy is suitable for use as a therapeutic strategy to reduce anxiety-related disorders, including PTSD.