APLN and renovascular hypertension: Therefore, as reno-vascular hypertension is associated with changes in the endogenous opioid system (18), and opioids are currently used for managing conditions like myocardial infarction (MI) and stroke, the aim of this study was to evaluate the interaction between apelin/APJ and opioid/OPR systems regarding cardiac responses to apelin in an acute reno-vascular hypertension model and heterodimerization of these two receptors in these conditions.