Activity of vagal efferent fibres innervating the smooth muscle of the dog's cardia
Miolan, J.P.; Roman, C.
Journal de Physiologie 74(8): 709-723
1978
ISSN/ISBN: 0021-7948 PMID: 753924 Document Number: 125290
Experiments were performed on dogs in which the central end of the left thoracic vagus was sutured to the peripheral end of the left phrenic nerve. In such preparations, the activity of motor units of the reinnervated left hemidiaphragm indicated the activity of the vagal efferent fibers. After the left hemidiaphragm had been transformed into subcutaneous muscle, the discharge of vagal fibers which originally supplied the lower esophageal sphincter (cardia) was studied using electromyography in the anesthetized dog. Only fibers showing low frequency tonic discharge were dealt with. For some fibers (VIC ; N = 18), which also have a slow discharge frequency (1 < f < 3 spikes/s) stop firing soon after the onset of swallowing and remain silent until the end of esophageal peristalsis. At this time, i. e., when the bolus enters the stomach, the discharge starts again with an increased frequency (5 < mean frequency < 9 spikes/s). The behavior of the tonic vagal fibers during swallowing and their low discharge frequency strongly suggest that these fibers originally controlled the smooth muscle of the lower esophageal sphincter and excited an inhibitory VIC or an excitatory control VEC on this area.