“Disjunction” of Frog Neuromuscular Synapses by Treatment with Proteolytic Enzymes

Abstract

VERTEBRATE skeletal muscle fibres are surrounded by the ectolemma or basement membrane, a thin sheath of filamentous material. At the neuromuscular junction, the ectolemma occupies the synaptic cleft and is continuous with a similar material which surrounds the axon terminal and its Schwann cell covering¹ (Fig. I A). Changes in the ectolemma of atrophic muscles have been observed^{2, 3}, but little is known about the structure and function of this material. The study described here demonstrates that certain proteolytic enzymes selectively digest the ectolemmal sheath, and that concomitantly the motor nerve terminals and their associated Schwann cells dissociate from the muscle fibres.