There are widespread chemosensitive areas in the brain with varying effects on breathing. In the awake goat, microdialyzing (MD) 50% CO2 at multiple sites within the medullary raphe increases pulmonary ventilation (V̇i), blood pressure, heart rate, and metabolic rate (V̇o2) (), while MD in the rostral and caudal cerebellar fastigial nucleus has a stimulating and depressant effect, respectively, on these variables (). In the anesthetized cat, the pre-Bötzinger complex (preBötzC), a hypothesized respiratory rhythm generator, increases phrenic nerve activity after an acetazolamide-induced acidosis (, ). To gain insight into the effects of focal acidosis (FA) within the preBötzC during physiological conditions, we tested the hypothesis that FA in the preBötzC during wakefulness would stimulate breathing, by increasing respiratory frequency (f). Microtubules were bilaterally implanted into the preBötzC of 10 goats. Unilateral MD of mock cerebral spinal fluid equilibrated with 6.4% CO2 did not affect V̇i, tidal volume (Vt), or f. Unilateral MD of 25 and 50% CO2 significantly increased V̇i and f by 10% (P < 0.05, n = 10, 17 trials), but Vt was unaffected. Bilateral MD of 6.4, 25, or 50% CO2 did not significantly affect V̇i, Vt, or f (P > 0.05, n = 6, 6 trials). MD of 80% CO2 caused a 180% increase in f and severe disruptions in airflow (n = 2). MD of any level of CO2 did not result in any significant changes in mean arterial blood pressure, heart rate, or V̇o2. Thus the data suggest that the preBötzC area is chemosensitive, but the responses to FA at this site are unique compared with other chemosensitive sites.
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