Vasomotor Responses to Laryngeal Nerve Stimulation

The changes in laryngeal blood flow were measured during electrical stimulation of the vagus, recurrent, and superior laryngeal nerves in 11 dogs. Blood flow volume was measured by collecting the entire laryngeal venous outflow per 15 second period stimulation. An approximately 30% increase in blood flow volume was produced by stimulation of the vagus and recurrent laryngeal nerves whereas a 20% decrease from control levels was obtained by stimulation of the superior laryngeal nerve. In seven dogs pretreated with atropine, stimulation of either the vagus or the recurrent laryngeal nerve did not cause any significant change in blood flow volume, while stimulation of the superior laryngeal nerve induced the expected 20% reduction in blood flow volume. Stimulation of any of the three laryngeal nerves did not affect heart rate or the femoral venous outflow. Administration of atropine did not affect laryngeal muscle action potentials. It is postulated that the vasomotor responses in laryngeal vessels are mediated via all three laryngeal nerves tested. The adrenergic vasoconstrictor responses seemed to be derived mainly from the superior laryngeal nerve, while the cholinergic vasodilator effect is more marked in the vagus and recurrent laryngeal nerves.