Innervation and the regulation of acetylcholinesterase activity during the development of normal and dystrophic chick muscle

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Abstract
Two isozymes of acetylcholinesterase (AChE) in the skeletal muscles of the chick embryo decrease to very low levels after hatching. These isozymes have been shown to be maintained in fast twitch muscles, the superficial pectoral and biceps brachii, of birds homozygous for inherited muscular dystrophy. Histochemical studies are presented that associate these isozymes with diffuse AChE activity in the sarcoplasm of embryonic and dystrophic muscle fibers.The hypothesis that neural activity inhibits the activity of the embryonic AChE forms in normal but not in dystrophic muscle after hatching was supported by the fact that biceps muscles of normal chicks denervated at two days still retained embryonic AChE activity when examined one month after denervation. In addition embryonic AChE forms reappeared within three days after denervation in muscles from month old chicks. One month after surgery, total AChE activity of denervated normal muscle was three to four times that of the controls. Moreover, unlike the normal, the AChE activity of dystrophic biceps muscle did not increase following denervation. Tenotomy of muscles from month old chicks had little effect on AChE activity.