REN and hypertensive disorder: In this context, the (mREN2)27 transgenic rat model of HTN, characterized by the overexpression of the mouse Ren-2d gene (Renin 2 tandem duplication of Ren1) in the brain and adrenal gland as well as a reduction in kidney renin, provides a valuable tool for studying the neural control of arterial pressure and cardiac excitation–contraction coupling.