[Electrical activity of the hearts of Hypophthalmichtus molitrix fish during cooling and warming]

In cold-unadapted H. molitrix, studies have been made on the electrical activity of the heart during cooling from 28 to 0 degrees. Cooling of the fish results in the increase of the duration of all ECG components and the decrease in their amplitude. The spontaneous activity gradually disappears, first in sino-atrium zone, then in atrium-ventricular one. Sinus rhythm disappeared at the abdominal temperature 3 degrees. The decrease in the heart rate was followed by its complete block without any extrasystoles and fibrillation. Warming of the fish up to the initial temperature (28 degrees) resulted in the recovery of cardiac activity, first in the atrium-ventricular zone, then in sino-atrium one.