Antidromic activation of vagal and sympathetic afferents does not produce intestinal contractions in dogs.
The question has been asked whether vagal and sympathetic afferents activated antidromically play a role as motor nerves on the in vivo small intestine in dogs anesthetized with urethane. The vagus nerve of one side was cut above the nodose ganglion and the efferent fibers allowed to degenerate. Peripheral stimulation (5-50 Hz, 0.5-3 ms, 5-25 V) of an intact cervical vagus, being able to excite both efferent and afferent fibers, caused large contractions in the jejunum and stomach, whereas stimulation of the contralateral cut cervical vagus could not produce any response in the jejunum but small contractions in the stomach. Peripheral stimulation of the cut cervical vagus did not produce bradycardia and hypotension. Single- and multi-unit discharges to distension of the jejunal segments could be recorded from the peripheral cut end of the cut cervical vagus. Immunohistochemically, there were many substance P-containing cells in both nodose ganglia. Antidromic stimulation of the dorsal roots (T7-T10) did not induce any response in the jejunum but contractions in the stomach. The results may confirm that vagal and sympathetic afferents have no antidromic motor function at least in the in vivo canine small intestine.