Central vs. peripheral chemoreceptors in ventilatory stimulation by Hacetate

Abstract

Intravenous infusion of Hacetate in conscious rabbits induces a greater decrease in cerebrospinal fluid (CSF) [HCO3-] and arterial CO2 partial pressure (PaCO2) than does HCl, HNO3, or Hacetate. To test whether acetate per se can stimulate central chemoreceptors, HCl- or Hacetate-acidified mock CSF was infused via the cisterna magna in conscious rabbits with catheters preimplanted under anesthesia. HCl infusion induced a greater decrease in PaCO2 refuting this hypothesis. To evaluate the role of the carotid body HCl and Hacetate were infused intravenously in an intact (CB+) and a chemodenervated group (CB-). In CB+ rabbits Hacetate infusion produced a greater decrease in PaCO2. In CB- rabbits, the fractional decrease in arterial PaCO2 was less for both acids compared with that of the CB+ rabbits, but it was significantly greater for Hacetate infusion (21.2 +/- 2.5%, mean +/- SE) than for HCl infusion (14.5 +/- 1.8%). Thus the carotid body is not necessary for the greater Hacetate ventilatory stimulation. The working hypothesis is that nonionic diffusion of Hacetate into brain or acetate replacement of HCO3- in CSF production lowers [HCO3-] near central chemoreceptors.