Fourier transform analysis of rabbit detrusor autonomous contractions reveals length-dependent increases in tone and slow wave development at long lengths

Abstract

Introduction

Bladder wall muscle (detrusor) develops low amplitude rhythmic contractions ( LARC). The activity of LARC is increased in detrusor from patients with overactive bladder. In this in vitro study, we used Fast Fourier Transforms (FFT) to assess the length-dependency of LARC components

Materials & Methods

Strips of rabbit detrusor were placed in a muscle bath between two clips to adjust length and record isometric tension. Tissues stretched from 70% to 130% of a reference muscle length (Lref) at 10% increments were allowed to develop LARC at each length for 20 min. LARC data were analyzed using FFT and represented by a frequency rather than time spectrum.

Results

Based on FFT analyses summarized by signal peaks within specific frequency ranges, rabbit LARC waveforms were divided into 1 tonic and 2 phasic components defined as A0+A1F1+A2F2. A0 is a length-dependent basal tonic component that increases linearly. A1F1 is a fast wave with a length-dependent specific amplitude (A1) and length-independent constant frequency (F1) of ~0.2 Hz, and A2F2 is a slow wave with a length-dependent amplitude (A2) and frequency (F2).

Conclusions

FFT analysis revealed that rabbit LARC consists of a basal tonic component plus 2 phasic components. The amplitudes of all 3 components were length-dependent. The frequency of the fast component was not length dependent, and the slow component was absent at short muscle lengths, developing only at muscle lengths beyond that producing a maximum active contraction.

http://www.jurology.com/article/S0022-5347(13)00347-9/abstract