Desensitization to acetylcholine at motor end plates in normal humans, patients with myasthenia gravis, and experimental models of myasthenia gravis.
Desensitization to ionophoretically applied ACh at the motor end plates of normal humans and patients with MG was studied. The pattern of desensitization at the normal human motor end plate was completely consistent with that observed in muscles of various animals. At motor end plates of MG patients there was greater desensitization and slower recovery from desensitization than in normals. A similar pattern of desensitization was observed at normal end plates when they were exposed to serum globulins of MG patients, and at end plates of muscles from mice than were repeatedly injected with serum globulins of MG patients. Despite the reported reduction in the number of ACh receptors, our calculations show that there is a large pool of spare receptors forming a sizeable margin of safety at the end plates of MG patients. The number of receptors may not show additional progressive reduction in number during repetitive motor activity. Our results indicate that desensitization could play a significant role in the development of neuromuscular block following repetitive motor activity in MG patients. The mechanism by which desensitization is augmented in MG patients in not yet clear.
D000109:Acetylcholine / Q000008:administration & dosage / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D006801:Humans; D066298:In Vitro Techniques; D007366:Intercostal Muscles / Q000503:physiopathology; D007478:Iontophoresis; D051379:Mice; D008815:Mice, Inbred Strains; D009045:Motor Endplate / Q000503:physiopathology*; D009132:Muscles / Q000503:physiopathology; D009157:Myasthenia Gravis / Q000097:blood / Q000503:physiopathology*; D009469:Neuromuscular Junction / Q000503:physiopathology*; D012712:Serum Globulins / Q000502:physiology
D012712:Serum Globulins; D000109:Acetylcholine