OSCILLATIONS IN SYMPATHOVAGAL BALANCE OPPOSE VARIATIONS IN DELTA-WAVEACTIVITY AND THE ASSOCIATED RENIN RELEASE

To determine the potential role of the sympathetic nervous system in t he generation of the oscillations in PRA over the 24-h period, we used the autocorrelation coefficient of RR interval (rRR), a new tool to e valuate the sympatho-vagal balance continuously. We determined the inf luence of the sympathetic nervous system both on the nocturnal PRA osc illations associated to increases in delta-wave activity and on the da ytime oscillations that occur randomly in awake subjects. PRA and rRR were determined every 10 min during 24 h in nine healthy subjects unde r continuous bed rest. Electroencephalographic spectral analysis was u sed to establish the variations in delta-wave activity during sleep, f rom 2300-0700 h. The overnight profiles in PRA, rRR, and delta-wave ac tivity were analyzed using a modified version of the pulse detection p rogram ULTRA. The temporal link among the profiles of rRR, PRA, and de lta-wave activity was quantified using crosscorrelation analysis. Duri ng sleep, large oscillations in PRA were strongly linked to variations in delta-wave activity. They were preceded by opposite oscillations i n rRR, decreases in rRR reflecting predominant vagal activity, and inc reases in rRR reflecting sympathetic dominance. During the waking peri ods, the levels of rRR were higher, with smaller variations. The dayti me PRA oscillations were not associated with any significant changes i n rRR, and conversely, significant oscillations in rRR were not follow ed by any significant changes in PRA. In conclusion, the sympathetic n ervous system is not directly involved in the generation of renin osci llations observed under basal conditions. During sleep, the oscillatio ns in sympatho-vagal balance are inversely related to the variations i n delta-wave activity and the associated renin release. The processes that give the intermittent signal for concomitant increases in slow wa ve activity and renin release from the kidney remain to be identified.