Dynamics of cardiac activity and the p wave of the electrocardiogram with stimulation of the vagus following disruption of the inhibitory effect

Summary

Acute experiments were performed on dogs under morphine-urethane anesthesia. A study was made of the cardiac activity and dynamics of the ECGP wave with relation to the value of the mean arterial pressure and the rhythm of cardiac activity in prolonged stimulation of the peripheral section of divided vagus after inhibition disruption (vagus-escape). As demonstrated, in prolonged stimulation of the peripheral section of the vagus after vagus-escape the sinus rhythm appears with the frequency of cardiac contractions of 50–60 per minute and with the achievement of the mean arterial pressure of 70–80% of the initial level. The stable form of cardiac contractions thus established resembles the effect on the heart of the vaguscenter characterized by slowed down rhythm of cardiac activity with retention of large systolic blood volume, maintaining the mean arterial pressure at a sufficiently high level. Atrioventricular rhythm and artioventricular block were observed with a lower mean arterial pressure and a slower rhythm of cardiac contraction.