The Response of Denervated Skeletal Muscle to Succinylcholine

The responses of denervated and normal canine gastroenemius muscle to succinylcholine (SCh) were compared and contrasted in regard to potassium (K+) flux &OV0312;O2, muscle tension, and electrical activity. K+ efflux and &OV0312;O2 of denervated muscle increased 20-fold and fourfold after SCh, respectively, while K+ efflux and &OV0312;O2, of normal muscle did not change and initially doubled, respectively. Denervated muscle responded to SCh with a contracture, as manifested by a prolonged increase in muscle tension and by prolonged electrical silence and inexcitability. Prior treatment with gallamine in paralyzing doses prevented increases in K+ flux and &OV0312;O2; small doses of gallamine attenuated these increases but did not block them. These effects arc probably related to an increase in sensitivity of the muscle membrane that develops following denervation such that SCh produces a mass depolarization of the muscle, diffusely increasing membrane permeability to Na+ and K+ and thereby stimulating the Na+/K+ pump.