An actuator is provided for a two-part stabilizer, which builds up a spring rate in its opened position. A hydraulic absorbing unit (9) is arranged on the axle of the switchable coupling unit (8). The absorbing unit is connected to one stabilizer part (4), on the one hand, and to the other stabilizer part (5), on the other hand. The absorbing unit forms at least one pressure chamber (32) and a suction chamber (33) and assumes a blocked position in the locked position of the switchable coupling (8) and counteracts the relative twisting motion between the two stabilizer parts (4, 5) at a hydraulic spring rate in the opened position of the switchable coupling (8).