Microvibration: capable of inducing spontaneous contractions in smooth muscles

Spontaneous contractions were elicited by the vibration of small amplitude (microvibration) imposed upon the quiescent strips prepared from the ureter and portal vein of dogs. An acceleration of the existing rhythm in the spontaneously contracting strips was also brought about by microvibration. Frequencies and amplitudes of microvibration ranged from 1 to 90 Hz and from 50 to 150 mum, respectively. Imposed cyclic strains were less than 1% at their maximum. Up to the amplitude of 150 mum, the greater the amplitude, the faster the induced rhythm. Stepwise increase of the frequencies up to 30 Hz brought about a gradual acceleration of rhythmicity. At frequencies of above 30 Hz, no appreciable frequency-dependent differences were observable among the responses induced. Local adrenergic mechanism proved to have nothing to do with these effects.