A Rapid Method for Demonstrating Skeletal Muscle Motor Innervation in Frozen Sections

Abstract

Longitudinal 50-100 .mu.m-thick frozen sections of [human] muscle were picked up on slides coated with 3% EDTA and after drying were incubated to demonstrate acetylcholinesterase. Subsequent incubation in 0.5% K3Fe(CN)6 was followed by fixation for 30 min in formol-calcium or formol-saline. After washing, the slides were incubated in 20% aqueous AgNO3 containing 0.1% CuSO4 for 2-30 min at 37.degree. C. Following development in a 1% solution of quinol (w/v) 5% with respect to Na2SO3 (w/v), axons and subneural apparatus stained dark brown to black in contrast to the less well stained muscle fibers and nuclei. This procedure permits study of the pattern of neuromuscular innervation in skeletal muscle 3 1/2-4 h after receipt of a sample, and makes possible determination of the terminal innervation ratio.