I.P. Butkevich - Dr. Sc. (Biol.), Leading Research Scientist, I.P. Pavlov Institute of Physiology, RAS (St.-Petersburg). E-mail: irinabutkevich@yandex.ru; V.A. Mikhailenko - Ph.D. (Biol.), Senior Research Scientist, I.P. Pavlov Institute of Physiology, RAS (St.-Petersburg). E-mail: viktormikhailenko@yandex.ru