<b>Effects of dibucaine on skinned skeletal muscle fibers. An example of multiple actions of a drug on a single subcellular </b><b>structure </b>

Abstract

The effects of a local anesthetic, dibucaine, on skinned fibers of amphibian skeletal muscle were examined. The drug showed multiple actions both on the sarcoplasmic reticulum (SR) and on the contractile system, i. e., 1) inhibition of active Ca uptake by the SR, 2) acceleration of the Ca-induced Ca release mechanism in the SR, 3) increase in Ca permeability of the SR membrane through a mechanism other than the Ca-induced Ca release, 4) increase in the Ca sensitivity of the contractile system, and 5) depression of maximum tension developed at a saturating concentration of Ca. The first three actions of dibucaine on the SR were proved to be mutually independent from 'each other, neither of them being a result of the others. KEY WORDS dibucaine / sarcoplasmic reticulum / contractile system / calcium / calcium-induced calcium release / skinned fiber