Non‐equivalence of impulse blockade and denervation in the production of membrane changes in rat skeletal muscle.

Abstract

A complete and long lasting blockade of nerve impulses was established in the sciatic nerve of rats, by implanting silastic cuffs of critical internal diameters. Marcaine-impregnated or plain cuffs were used. The contralateral sciatic nerve was sectioned. At various days after the initial procedures, the extensor digitorum longus muscles of the 2 sides were examined with intracellular electrodes. Decrease in resting membrane potential, fibrillatory activity and resistance of action potential to tetrodotoxin developed in the denervated and in the impulse-blocked muscles. In the latter, fibers were normally innervated since they displayed miniature end-plate potentials and were excitable by nerve stimulation distal to the blocking cuff. All of the above mentioned denervation-like changes were significantly less pronounced in blocked muscles than in denervated ones. In addition to loss of nerve impulses, some other neural factor must be taken into account to explain the origin of muscle changes induced by denervation. The possible relation of this additional factor with nerve degeneration is discussed.