Effects of hypoxia on cardiac vagal efferent activity and on the action of the vagus nerve at the heart in the dog.

The discharge of cardiac efferent fibres in the central end of the transected vagus nerve was studied in single or few-fibre preparations in anaesthetized dogs. At the same time standard electrical stimuli were delivered to the cardiac end of the vagus nerve. During progressive asphyxic hypoxia induced by tracheal occlusion cardiac vagal activity increased and vagal action on the heart was potentiated.