Reduced NO enhances the central gain of cardiac sympathetic afferent reflex in dogs with heart failure

The aim of the present study was to test the hypothesis that a decrease in central nitric oxide (NO) is involved in the enhancement of the central gai n of the cardiac "sympathetic afferent" reflex (CSAR) in dogs with congesti ve heart failure (CHF). Thirteen dogs with pacing-induced CHF and sixteen s ham dogs were anesthetized with alpha-chloralose and were baroreceptor dene rvated and vagotomized. The CSAR was evoked by stimulation of the left vent ral ansa. A lateral cerebroventricular cannula was inserted to deliver sodi um nitroprusside (SNP) and N-G-nitro-L-arginine methyl ester (L-NAME). Arte rial pressure, heart rate, and renal sympathetic nerve activity (RSNA) were recorded at baseline and during elicitation of the CSAR. We found that I) the responses of RSNA to stimulation were augmented in dogs with CHF, 2) SN P depressed the increase in RSNA induced by the CSAR in CHF dogs but had no effect in sham dogs, and 3) L-NAME potentiated the CSAR-induced increase i n RSNA in sham dogs but not in dogs with CHF. We conclude that reduced cent ral NO is involved in the enhanced central gain of the CSAR in CHF dogs.