The influence of the vagus nerve and indole derivative SS-68 on excitation processes in the SA node oleh Anatoliy A. Nechepurenko, Pavel A. Galenko-Yaroshevsky, Vladimir M. Pokrovskiy, Anait V. Zelenskaya, Konstantin F. Suzdalev, Svetlana A. Lebedeva, Natalia M. Makhnova, Alexandr V. Maksemyuk, Ivan A. Minenko, Roman V. Nikitin, Valeriy G. Abushkevich