Electrical signals of the urinary bladder under neurostimulation and anticholinergics: Real EMG or chaos?

Signals recorded from the detrusor vesicae in vivo cannot be proven to orig inate from smooth muscle since the abolition of all possible influences on the signal is impossible. Our objective was to gain additional information about the underlying dynamic system using algorithms from digital speech an alysis and nonlinear dynamics. Previously recorded signals from the detruso r in 10 minipigs under sacral anterior root stimulation (SARS), before and after administration of anticholinergics, were re-analyzed with Wavelet-Tra nsformation (WT). After reconstruction of the attractors, correlation dimen sion (CD, complexity), central tendency measure (CTM, variability) and Lyap unov exponents (LE, chaoticity) were calculated. The signal under SARS appe ars less complex, less chaotic, but more variable than the native signal. U nder the influence of anticholinergics, the base line values for CD and LE are about doubled. The dynamic system generating these signals obviously re sponds in a characteristic manner to the experimental settings. SAPS brings order to the system, whereas this order is disturbed by anticholinergics. This and the correlation with bladder pressure indicate that signals record ed from the urinary bladder are at least in part myogenic and hence a real detrusor EMG.