CHARACTERISTICS OF RENAL SYMPATHETIC-NERVE ACTIVITY IN EXPERIMENTAL CONGESTIVE-HEART-FAILURE IN THE RAT

Recently emerging evidence has indicated that efferent renal sympathet ic nerve activity (RSNA) is increased in congestive heart failure (CHF ). In the present study the cyclic activity of the renal nerve in the normal and CHF rat was studied. An ischaemic myocardial lesion resulti ng in CHF was induced by left coronary artery ligation. Sham-operated rats subjected to thoracotomy served as normal controls. Renal sympath etic nerve activity was recorded under chloralose anaesthesia. The neu ral cycle activity was significantly higher in CHF (47 +/- 3 %) compar ed with sham-operated rats (34 +/- 3 %, P < 0.005). Baroreceptor contr ol of RSNA was significantly attenuated in CHF compared with normal co ntrol rats (P < 0.005). In response to noxious thermal stimulation by 48 degrees C water immersion of the tail tip, the increase of RSNA was significantly higher in CHF compared with sham-operated rats. A stepw ise 15 % blood volume expansion over 5 min which induced no alteration s of blood pressure or heart rate (HR) resulted in a gradual decrease of RSNA in control rats by approximately 25 % at the end of the volume expansion procedure. In CHF rats however, there was no significant ch ange in RSNA during volume expansion. It is concluded that in CHF rats : (1) efferent RSNA is increased; (2) baroreceptor control of RSNA is decreased; (3) RSNA in response to cutaneous thermal noxious stimulati on is exaggerated; and (4) RSNA inhibition by cardiopulmonary receptor s is blunted.