The present invention relates generally to the field of ligands for nicotinic acetylcholine receptors, activation of nACh receptors, and the treatment of disease conditions associated with defective or malfunctioning nicotinic acetylcholine receptors, especially of the brain. The retainer cage includes a web portion and a plurality of legs extending from the web portion toward the surface of the component part. Thereby, path pressure loss increases, a PCV flow rate is decreased, and blowby gas can be passed through a separator with a high collection efficiency. The central aperture guides and aligns an actuator rod.