Functional anatomy of the vagal innervation of the cervical trachea of thedog

The canine cervical trachea has been used for numerous studies regarding th e neural control of tracheal smooth muscle. The purpose of the present stud y was to determine whether there is lateral dominance by either the left or right vagal innervation of the canine cervical trachea. In anesthetized do gs, pressure in the cuff of the endotracheal tube was used as an index of s mooth muscle tone in the trachea. Alter establishment of tracheal tone, as indicated by increased cuff pressure, either the right or left vagus nerve was sectioned followed by section of the contralateral vagus. Sectioning th e right vagus first resulted in total loss of tone in the cervical trachea, whereas sectioning the left vagus first produced either a partial or no de crease in tracheal tone. After bilateral section of the vagi, cuff pressure was recorded during electrical stimulation of the rostral end of the right or left vagus. At the maximum current strength used, stimulation of the le ft vagus produced tracheal constriction that averaged 28.5% of the response to stimulation of the right vagus (9.0 +/- 1.8 and 31.6 +/- 2.5 mmHg, resp ectively). In conclusion, the musculature of cervical trachea in the dog ap pears to be predominantly controlled by vagal efferents in the right vagus nerve.