Changes in the inspiratory pattern contribute to modulate the sympathetic activity in sino-aortic denervated rats

Abstract

The activity of pre-sympathetic neurons is under respiratory modulation and changes in the central respiratory network may impact on the baseline sympathetic activity and mean arterial pressure (MAP). It is well known that after baroreceptor afferents removal (sino-aortic denervation, SAD), rats present an unexpected normal levels of MAP. We hypothesized that changes in the respiratory pattern and in the respiratory modulation of the sympathetic activity contribute to keep the sympathetic outflow in a normal range of variation in absence of arterial baroreceptors in rats. To study these mechanisms, we recorded perfusion pressure as well as the activities of phrenic and thoracic sympathetic nerves (tSNA) in male juvenile rats using the working heart-brainstem preparation. The time of inspiration significantly increased in SAD rats, and this change was not dependent on the carotid bodies or on the vagal afferents. However, no changes were observed in the perfusion pressure as well as in the baseline tSNA in all phases of the respiratory cycle in SAD rats. Our data show that in spite of longer inspiratory activity, the baseline sympathetic activity is maintained at normal level in SAD rats. These findings indicate that the respiratory-sympathetic coupling is normal after SAD and suggest that the respiratory modulation of sympathetic activity is maintained within normal range after the removal of arterial baroreceptors.

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