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1Department of Physiology, Medical College of Wisconsin Milwaukee, 2Zablocki Veterans Affair Medical Center, and 3Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin
Submitted 14 September 2004 ; accepted in final form 30 November 2004
Our aim was to determine the effects of carotid body denervation (CBD) on the ventilatory responses to focal acidosis and ibotenic acid (IA) injections into the medullary raphe area of awake, adult goats. Multiple microtubules were chronically implanted into the midline raphe area nuclei either before or after CBD. For up to 15 days after bilateral CBD, arterial PCO2 (PaCO2) (13.3 ± 1.9 Torr) was increased (P < 0.001), and CO2 sensitivity (–53.0 ± 6.4%) was decreased (P < 0.001). Thereafter, resting PaCO2 and CO2 sensitivity returned (P < 0.01) toward control, but PaCO2 remained elevated (4.8 ± 1.9 Torr) and CO2 sensitivity reduced (–24.7 ± 6.0%) 
40 days after CBD. Focal acidosis (FA) at multiple medullary raphe area sites 23–44 days post-CBD with 50 or 80% CO2 increased inspiratory flow (
I), tidal volume (VT), metabolic rate (O2), and heart rate (HR) (P < 0.05). The effects of FA with 50% CO2 after CBD did not differ from intact goats. However, CBD attenuated (P < 0.05) the increase in I, VT, and HR with 80% CO2, but it had no effect on the increase in O2. Rostral but not caudal raphe area IA injections increased I, BP, and HR (P < 0.05), and these responses were accentuated (P < 0.001) after CBD. CO2 sensitivity was attenuated (–20%; P < 0.05) <7 days after IA injection, but thereafter it returned to prelesion values in CBD goats. We conclude the following: 1) the attenuated response to FA after CBD provides further evidence that the carotid bodies provide a tonic facilitory input into respiratory control centers, 2) the plasticity after CBD is not due to increased raphe chemoreceptor sensitivity, and 3) the "error-sensing" function of the carotid body blunts the effect of strong stimulation of the raphe.
control of breathing; CO2 chemoreception; peripheral chemoreception
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