Sy. Sun et al., Enhanced peripheral chemoreflex function in conscious rabbits with pacing-induced heart failure, J APP PHYSL, 86(4), 1999, pp. 1264-1272
The present study aimed to determine whether peripheral and/or central chem
oreflex function is altered in chronic heart failure (CHF) and whether alte
red chemoreflex function contributes to sympathetic activation in CHF. A ra
bbit model of pacing-induced CHF was employed. The development of CHF (3-4
wk of pacing) was characterized by an enlarged heart, an attenuated contrac
tility, and an elevated central venous pressure. Renal sympathetic nerve ac
tivity (RSNA) and minute volume (MV) of ventilation in response to stimulat
ion of peripheral chemoreceptors by isocapnic/hypoxic gases were measured i
n the conscious state. It was found that the baseline RSNA at normoxia was
higher in CHF rabbits than in sham rabbits (35.00 +/- 4.03 vs. 20.75 +/- 2.
87% of maximum, P < 0.05). Moreover, the magnitudes of changes in RSNA and
MV in response to stimulation of the peripheral chemoreceptors and the slop
es of RSNA-arterial PO2 and MV-arterial Po, curves were greater in CHF than
in sham rabbits. Inhibition of the peripheral chemoreceptors by inhalation
of 100% O-2 decreased RSNA in CHF but not in sham rabbits. The central che
moreflex function, as evaluated by the responses of RSNA and MV to hyperoxi
c/hypercapnic gases, was not different between sham and CHF rabbits. These
data suggest that an enhancement of the peripheral chemoreflex occurs in th
e rabbit model of pacing-induced CHF and that the enhanced peripheral chemo
reflex function contributes to the sympathetic activation in the CHF state.