Effects of initial length on intrinsic tone in guinea pig tracheal smooth muscle

The effect of the initial muscle length (Li) on intrinsic tone (IT) in electrically stimulated guinea pig has been studied. The research seeks to find out if the amplitude of relaxation can determine the amount of intrinsic tone and measure the relationship between the active isometric force and the initial length. Experiments were done on tracheal segments of Hartley guinea pigs weighing 300 to 350 grams. Results show that Li regulates IT and the maximum extent of relaxation. It has also been observed that relaxation indicates a transient and incomplete inhibition of intrinsic tone.