An actuator comprising a body in which a rod is mounted to slide, the actuator including a screw extending inside the rod to co-operate with a nut secured to the rod, the screw being driven in rotation by a motor. The rod is associated with a piston that slides in a cavity of the body so as to define two chambers therein, the chambers being filled with hydraulic fluid and being put into communication via fluid transfer means fitted with at least one regulator member adapted to throttle the fluid expelled from one of the chambers, in at least one travel direction of the rod.