1. Department of Physiology, University of Oslo, POB 1103, N‐0317 Oslo, Norway
2. Cold Spring Harbor Laboratory, Jones 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
3. Department of Pharmacology, University of Virginia School of Medicine, 1300 Jefferson Park Avenue, Charlottesville, VA 22908, USA
4. Abteilung Zellphysiologie, Max‐Planck‐Institut für medizinische Forschung, Jahnstrasse 29, Heidelberg D‐69120, Germany