1. Department of Biology; Animal Physiology Group, University of Kaiserslautern; Erwin Schroedinger-Strasse 13 Kaiserslautern Germany
2. Institute of Neurobiology, Universitaetsstasse 1, Heinrich Heine University Duesseldorf; Duesseldorf Germany
3. Medical Faculty; Institute of Cellular Neurosciences, University of Bonn; Sigmund-Freud-Strasse 25 Bonn Germany