Since the time of Bainbridge, stretch of the atrium is known to produce a reflex response but conflicting results have been reported as to what reactions are involved. In choralose anesthetized (70 mg/kg) dogs, the activity of both sympathetic and vagal nerves to the heart were recorded simultaneously. Possible inclusion of sympathetic fibers in the vagal efferents used was prevented by section of all branches of ipsilateral stellate glanglion except white rami. Stretch of the right atrium for 60 sec, produced an increase in heart rate caused by both reflex and myogenic actions. The sympathetic nerve activity was greatly augmented, while in the vagus activity increased slowly. At the end of stretch there was a transient inhibition in activity of both nerves. Stretch of the left atrium produced first a reduction and then an increase in heart rate; sympathetic nerve activity was profoundly inhibited for 10-20 sec, followed by augmentation which outlasted the stimulus for more than 30 sec. Vagal activity was augmented from the beginning of the stretch. The authors observed that reciprocal action between the two autonomic nerves did not occur except in the early phase of the stretch and that the changes in heart rate reflected mainly the sympathetic activity.
|Pages (from-to)||No. 1136|
|Publication status||Published - Jan 1 1977|
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