The sequence of changes in cholinesterase activity during reinnervation of muscle

Abstract

The following evidence supports the view that cholinesterase (ChE) activity of muscle is regulated by its nerve supply: denervation produces a more rapid decrease in ChE than in total protein, and tenotomy produces loss of protein without change in ChE. The present study concerns changes in ChE during regeneration of nerve fibers into denervated muscle. In twenty rats the nerve to the sternomastoid was crushed at the muscle. Alternate, frozen, serial, cross-sections of muscle were stained histochemically or assayed quantitatively for ChE. Sole-plate ChE was distinguished from background or non-sole-plate ChE by comparing regions of muscle having sole plates with regions of muscle lacking them. Background ChE and sole-plate ChE both decreased to 68% of normal at 1 week postoperatively and increased gradually to 93% of normal by 6 weeks. The ratio of background ChE to sole-plate ChE was constant at 1, 3, and 6 weeks, indicating a similar rate of reappearance of enzyme at both sites. Inasmuch as reinnervation of the muscle was probably complete at 2 weeks, the subsequent increase in ChE probably reflects a slow rate of synthesis rather than a slow addition of newly reinnervated muscle fibers. This slow, gradual synthesis following reinnervation contrasts markedly with the rapid decrease in ChE (40% in 3 days) following denervation. Total protein showed no similar gradual restoration, being about 93% of normal 1, 3, and 6 weeks postoperatively.