['In the present study, we investigated the effects of usnic acid (UA) on the endoplasmic reticulum (ER) stress processes in rat cardiomyocytes.', 'Gene expression of pro-inflammatory cytokines and activation of ER stress signaling were analyzed. Besides, levels of phosphorylated AMPK were measured to evaluate the mechanisms of UA. Finally, small interfering RNA (siRNA) oligos targeting AMPK subunits were used to determine the roles of AMPK in rat cardiomyocytes treated with UA.', 'We found that UA treatment significantly reduced ER stress activation and expression of pro-inflammatory cytokines, via an AMPK signaling-dependent manner.'] Does usnic acid inhibit ER stress activation through AMPK signaling pathway in rat cardiomyocytes?