Central-peripheral chemoreceptor interaction in awake cerebrospinal fluid-perfused goats.

We assessed the ventilatory interaction between central [central nervous system (CNS)] and peripheral chemoreceptor stimuli in five awake goats. CNS extracellular fluid (ECF) [H+] was altered with cisterna magna perfusion of mock CSF. Peripheral chemoreceptors were stimulated with three doses of NaCN given intravenously. The resulting dose-response curves were used to assess interaction of the central and peripheral stimuli. The observed interaction was hypoadditive; i.e., the average slope of the NaCN-inspired minute ventilation dose-response line was significantly greater during alkaline perfusion than during acidic perfusion. This correlation can be described by slope = -0.24 (CSF [H+]) + 30.7; r = 0.67 (P less than 0.01). Increased ventilatory responses were accompanied by increases in mean inspiratory flow, tidal volume, and breathing frequency and decreases in expiratory time in response to peripheral chemoreceptor stimulation. Unlike previous reports in anesthetized and denervated animals, in our awake intact goats the ventilatory and tidal volume responses showed no significant dependence on the level of control (pre-NaCN stimulus) inspired minute ventilation. We conclude that the level of [H+] in cerebral ECF exerts a significant reflex-mediated hypoadditive effect on the ventilatory responses to peripheral chemoreceptor stimulation.