Frequency of spontaneous contractions in longitudinal and transverse bladder strips

The frequency components of spontaneous contractility of rabbit bladder strips were examined with respect to their orientation and position. Spectra of longitudinal and transverse strips of bladder were studied in vitro in consecutively dissected segments from the same bladder. The frequency characteristics of these strips were characterized at rest and also with incremental extension to 125% of original length. Results show that transverse and longitudinal strips of bladder muscle undergo continuous spontaneous contractions in the frequency range of 0.01-0.25 Hz. The amplitude of the spontaneous contractions is not dependent on the amount of resting tension in either longitudinal or transverse strips. Longitudinal strips have a higher frequency of spontaneous variations of tension compared with the transverse strips. The amplitude of transverse strips is lowest at the base of the bladder, and the frequency components of activity increases in magnitude toward the bladder dome. Extension of transverse strips shows the generation of frequency peaks of tissues located at the middle of the bladder having a significantly lower rate of relaxation than the proximal or distal strips. Spontaneous contractility of the bladder indicates the presence of a potentially significant parameter that must be considered when tissue response to mechanical, electrical, or pharmacological stimulation is interpreted.