Effect of Denervation on the Histochemical Appearance of Cholinesterase at the Myoneural Junction

Abstract

THE sensitivity of the motor end-plate to acetyl-choline is known to increase after denervation. Many workers have investigated by chemical analysis the cholinesterase content of denervated muscle in an attempt to explain this increased sensitivity. The results have, however, been confusing. Marnay and Nachmansohn¹ reported that the cholinesterase content of muscle increased following nerve section, while Couteaux and Nachmansohn² and Stoerk and Morpeth³ found that it became reduced. Sawyer et al. ⁴, working on skeletal muscle of the rat, guinea pig and rabbit, reported that the concentration of cholin-esterase at first became reduced after nerve section and later became increased to considerably more than its normal complement. Since the results obtained by chemical analysis include the cholinesterase present in the terminal nerve fibres⁵ and also that present in muscle other than at the motor end-plate, it seemed desirable to investigate the problem using a histochemical method and to confine the study to the cholinesterase content of the motor end-plate.