Extrajunctional Acetylcholine Receptors: Alterations in Human and Experimental Neuromuscular Diseases

Diffuse extrajunctional acetylcholine receptors (AChR) of skeletal muscle fibers were readily visualized by light and electron microscopy in muscle biopsy specimens of experimental denervation and human denervating diseases by use of an α-bungarotoxin immunoperoxidase technique. In peripheral neuropathies and various motor neuron diseases, a significant number of muscle fibers appearing denervated by histochemical criteria have diffuse extrajunctional AChR like those experimentally denervated by cutting the motor nerve supply. In portions of muscle fibers experimentally deprived of neuronal influence by direct injury, diffuse extrajunctional AChR developed, demonstrating that a denervation-like diffuse appearance of extrajunctional AChR can develop other than with neuronal damage, ie, it can be myogenous. Similar extrajunctional AChR was seen in some regenerating fibers of human myopathies, especially inflammatory myopathies.