1. Department Excitable Structures, Institute of Biophysics & Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Bldg. 21, 1113 Sofia, Bulgaria
2. Department of Anesthesiology & Intensive Care, Military Medical Academy, St. Georgi Sofyiski Street, 3, 1606 Sofia, Bulgaria
3. Department of Human & Animal Physiology, Faculty of Biology, Sofia University “St. Kliment Ohridski”, 8 D. Tsankov Blvd., 1164 Sofia, Bulgaria