PRL and major depressive disorder: Furthermore, knockdown of IL-6R in PrL pyramidal neurons increased the number of spikes in comorbid rats (Fig. 6G), and the symptom of depression-like behaviors, such as the immobility time in FST (Fig. 6H), the center distance in OFT (Fig. 6I) and the spent time and entries in open arms in EPM (Fig. 6J), was also significantly improved following AAV–IL-6R–shRNA injection.