An active feedback system for isotonic studies of smooth muscle

A feedback system used to perform isotonic studies of smooth muscle is presented. This system is capable of applying a constant force to muscle samples regardless of their contractile activities. The force applied to the tissue is controlled using a proportional integral control system that drives a linear motor. The device is integrated into a sucrose gap tissue bath apparatus where measurements of displacement and electrical activity are also possible. The frequency of canine colonic smooth-muscle electrical oscillations was found to be positively related to applied force.