The cooperative phenomenon of autonomic nervous system in urine storage for Wistar rats

The fractal dimension (FD) and spectral frequencies of physiological signals are two important indices in the study of physiological functions and dynamical diseases. The first index can be used to characterize the intensity and the second the rhythms of signals embedded in seemingly random data. Recent studies using both indices verified that synergic co-activations of bladder and external urethral sphincter (EUS) of Wistar rats were present during the voiding of urine. In this study, the primary aims were to (1) examine if the involved muscles in the lower urinary tract would be under similar coactivations during the urine storage phase, and (2) characterize quantitatively the sympathetic and parasympathetic nerve activities simultaneously. Eighteen experiments were performed on six intact adult female Wistar rats and then the electromyogram of EUS and cystometrogram of bladder were analyzed. Results indicated that the EUS did not contain any significant spectral frequencies in the storage phase. Furthermore, its FDs (1.5918 +/- 0.0157) indicated that no appreciable amount of signal intensities was observed in the EUS. On the other hand, the bladder exhibited parasympathetic frequency of 8 Hz with signal-to-noise ratio (SNR) = 19.9001 decibel (dB) for group mean, and sympathetic frequency of 19 Hz with SNR = 22.8330 dB for group mean. In addition, its FDs (1.4796 +/- 0.0092) indicated relatively persistent intensities during storage, as compared to that of EUS (1.5918 +/- 0.0157) with statistical significance (P < 0.01). We concluded that the EUS was not activated during the phase of storage. The bladder was under the cooperative, not antagonistic, sympathetic and parasympathetic nerve activities with discernible rhythmic frequencies and persistent intensities.