Responses of smooth muscles to quick stretch; relation of stretch to conduction

Abstract

Quick stretches applied to isolated strips of visceral muscles elicit contractions and electrical responses, similar stretches elicit no responses from blood vessels and nictitating membrane. Highly excitable muscles gave repetitive responses. Spontaneously active taenia coli relaxed in response to stretch and electrical activity diminished correspondingly. The membrane potential (sucrose gap measurement) decreased during stretch; spikes appeared at a critical level of depolarization. A single initial spike sometimes occurred before membrane depolarization. The membrane potential of spontaneously active muscle increased during stretch. Strips of smooth muscle mechanically immobilized in the center showed conduction from one side to the other; signals for both activation and relaxation were conducted. It is concluded that conduction can occur in absence of stretch, that quick stretch can alter membrane potential and thus alter excitability of smooth muscle.