Role of respiratory changes on the modulation of arterial pressure in rats submitted to sino-aortic denervation

Sino-aortic denervated (SAD) rats present mean arterial pressure (MAP) similar to control rats. Since respiration modulates MAP, we hypothesized that conscious SAD rats present respiratory changes associated with the normal MAP. In this study we evaluated the cardiovascular and respiratory activities and arterial blood gases in control and SAD rats. Male juvenile Wistar rats (P19-P21) were submitted to SAD, sham surgery, or selective carotid bodies removal (CBX) and the three groups were evaluated 10 days after the surgery (SAD, n = 21, Sham, n = 18, CBX, n = 13). MAP in Sham, SAD and CBX was similar (P > 0.05), but the variability of MAP was significantly higher in SAD than in Sham and CBX rats (P < 0.0001). The duration of expiration and inspiration increased in SAD rats related to Sham and CBX rats, which resulted in a reduced respiratory frequency and minute ventilation (P < 0.05). PaO₂ and hemoglobin saturation were reduced in SAD and CBX related to Sham rats, while PaCO₂ was increased in SAD compared to Sham rats. The short and long-term respiratory variability were significantly higher in SAD than in Sham and CBX rats (P < 0.05). In addition, the falls of MAP during deep breaths were higher in SAD than in Sham and CBX rats (P < 0.0001). The data show that SAD rats present respiratory changes, which may be one of the compensatory mechanisms associated with the maintenance of normal levels of MAP in the absence of arterial baroreceptors.

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