Effects of carotid body sympathetic denervation on ventilatory acclimatization to hypoxia in the goat.

Our objective was to test the hypothesis that diminishing sympathetic input to the carotid body (CB) during prolonged exposure to hypoxia results in increased CB afferent activity and increased ventilatory drive. Six awake goats were studied prior to and following sectioning of the efferent sympathetic input to the CB from the superior cervical ganglion. Ventilatory responses to acute and prolonged isocapnic hypoxia (PaO2 40 Torr) and drugs (norepinephrine and dopamine, 0.5, 1.0 and 5.0 micrograms.kg-1 min-1) were collected prior to the denervation. One week and 3-4 weeks following the sympathetic denervation, the animals were restudied following the above protocol. Ventilation was significantly lower following sympathetic denervation in normoxia and during the hypoxic exposure. However, the response to acute hypoxia and the time-course of ventilatory acclimatization to hypoxia was not altered by sympathetic denervation. All doses of norepinephrine and dopamine significantly inhibited VE in a dose-dependent manner. Sympathetic denervation did not significantly alter the response to the drug infusions. The sympathetic innervation to the CB does not appear to play a role in either the acute or prolonged ventilatory responses to hypoxia in the awake goat, but may affect overall ventilation.