Journal of Applied Physiology, Vol 66, Issue 4 1635-1641, Copyright © 1989 by American Physiological Society
A vagally mediated response to metabolic acidosis in anesthetized rabbits
M. Maskrey and D. Trenchard
Department of Thoracic Medicine, University of London, Midhurst, West Sussex, United Kingdom.
Pentobarbital sodium-anesthetized rabbits received 10-min infusions of
acetic, lactic, or propionic acid delivered via a catheter to the right
atrium at a rate of 1 mmol/min (n = 14). Arterial [H+] increased by 35.8
+/- 7.6 (SD) nmol/l, a decrease in pH of 0.27 +/- 0.04. By the end of the
infusion period respiratory frequency (f), tidal volume (VT), and minute
ventilation (V) had increased by 15.5 +/- 6.2 breaths/min, 7.3 +/- 2.7 ml,
and 0.86 +/- 0.34 l/min, respectively. Arterial PCO2 (PaCO2) increased
initially, but isocapnia was established during the latter half of the
infusion (delta PaCO2 = 0.4 +/- 2.0 Torr). Bilateral cervical vagotomy
eliminated the f response to acid infusions (n = 9, delta f = 0.6 +/- 2.4
breaths/min). The increase in VT (12.6 +/- 3.1 ml) was greater, but that in
V (0.39 +/- 0.11 l/min) was less than in intact animals (P less than 0.05).
PaCO2 remained elevated throughout the infusion (delta PaCO2 = 5.5 +/- 2.6
Torr), resulting in a greater rise in arterial [H+] (delta[H+]a = 53.6 +/-
6.6 nmol/l, delta pHa = -0.37 +/- 0.04). It is concluded that vagal
afferents play a role in the f response to acute metabolic acidosis in
rabbits.
