1 Institute of Physiology, Department of Neurophysiology, Eberhard Karls University of Tübingen, Tübingen, Germany. Electronic address: olga.garaschuk@uni-tuebingen.de.
2 Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, United Kingdom; Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao 48011, Spain; Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, Vilnius LT-01102, Lithuania. Electronic address: Alexej.Verkhratsky@manchester.ac.uk.