Does stimulation of the left atrial receptors affect the activity in efferent vagal nerves to the heart in decerebrate dogs?

In anaesthetized dogs with an intact neuraxis, distension of small balloons at the pulmonary vein--atrial junctions to stimulate atrial receptors with myelinated vagal afferent nerves causes an increase in heart rate but does not influence the activity in efferent vagal cardiac nerves. However, it has been suggested from experiments performed in decerebrate dogs that stimulation of atrial receptors causes a tachycardia partly mediated by a decrease in activity in efferent vagal nerves. In the present study in chloralose-anaesthetized dogs, following total decerebration (four dogs) or partial decerebration (four dogs) at the level of the mid-brain, distension of the small balloons caused an increase in heart rate but did not affect the activity in efferent vagal nerve fibres which responded by an increase in activity to stimulation of carotid baroreceptors and chemoreceptors. These results show that stimulation of the left atrial receptors in totally or partially decerebrate dogs causes an increase in heart rate but does not influence the activity in efferent vagal cardiac nerves.