Why is jogging an antidepressant?

I pass on this brief description by Sarah Lemprière of work by Xia et al: 

Physical exercise can reduce depressive symptoms, and several brain regions have been implicated in this effect. However, the neural circuit mechanisms underlying this antidepressant effect are not yet known. Xia et al. used a chronic stress model to induce depressive-like behaviors in mice and found that daily treadmill exercise prevented these behaviors. They observed that oxytocin-releasing projections from the paraventricular nucleus to the nucleus accumbens were disrupted by stress and restored by exercise. Experimental inhibition of this circuit blocked the antidepressant effects of exercise, whereas activation prevented stress-induced depressive behaviors. The findings indicate that the oxytocinergic connection between these two brain regions is required for the antidepressant action of exercise and could be a future therapeutic target.