Weakened long-range correlation of renal sympathetic nerve activity in Wistar rats after anaesthesia

In this study we employed multiscale entropy (MSE) measurement to assess the long-range temporal correlation (LRTC) of multifibre renal sympathetic nerve activity (RSNA) signals in conscious and anaesthetized Wistar rats. It was found that both groups presented more complex MSE profiles than an uncorrelated process. Moreover, the results of MSE analysis of RSNA demonstrated that the entropy values, derived from the conscious group, increased on small time scales and then stabilized to a relatively constant value, however, the entropy measure, derived from animals with anaesthesia, almost monotonically decreased. The present study shows that while LRTC in the temporal dynamics of energy fluctuations of RSNA does not implicate a unique mechanism, the data for the first time provide evidence of much less temporal correlation in anaesthetized condition. This suggests the fractal properties of underlying dynamical system have been effectively eliminated by anaesthesia. These results demonstrate that apparently random fluctuations in multifibre RSNA are dictated by a complex deterministic process that imparts "long-term" memory to the dynamic system. However, this memory is significantly weakened by anaesthesia.