Heart activity during experimental diving of snakes

¹ The University Institute for Experimental Medical Research, Ullevaal Hospital, Oslo, Norway

Diving bradycardia has been demonstrated in snakes, (Tropidonotus natrix). The bradycardia was developed rapidly and amounted to a reduction in heart rate of about 85%. The electrocardiographic findings revealed the slowing of the heart rate as effected mainly through a prolongation of the diastole, amounting to 30 times the prediving value. Duration of the electrical systole showed a prolongation of the P-R interval by 15% and the Q-T interval by 130%. A rapid and pronounced shift in the T-wave amplitude occurred upon submersion. The results suggest that the described T-wave shifts are due to changes in concentration of CO₂ in the organism. Increased concentrations of CO₂ in the respiratory air induced bradycardia and had a depressant effect on respiration.