Enhanced peripheral chemoreflex function in conscious rabbits with pacing-induced heart failure

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.