Differential effect of stimulation of nucleus ambiguus on XXXX .

@entity235 @entity713 @entity11233 @entity1372 @entity2224 @entity1168
Acute experiments were performed on open-chest male mongrel @entity235 that were anesthetized with thiopental @entity1372 and respired. An average of 10 penetrations per side was used to explore the rostral-caudal organization of the nucleus ambiguus (NA) and the area ventrolateral to it. Atrial pacing was performed on some trials to clarify the occurrence of @entity713 . In addition, the vagi were sectioned in some animals to confirm the peripheral pathway of the observed effects. Finally, the twin-pulse technique was used to classify the neurons underlying the observed effects according to their refractory periods. Stimulation in the area of the NA and lateral to it produced @entity1168 and @entity1168 without altering blood pressure. Stimulation of either the left or right NA produced slowing of both @entity2224 . However, slowing of the atrial rate was greatest with right NA stimulation, whereas slowing of the ventricular rate was predominant with left-side stimulation. The presence of @entity713 was evident from dropped QRS complexes with and without pacing. Vagotomy demonstrated that these effects were conducted by ipsilateral but not contralateral nerves. Measurement of the refractory periods showed that the neurons underlying both @entity11233 were characteristic of B-fibers.
