Neuromuscular transmission in amyotrophic lateral sclerosis

• Published in: Muscle & nerve Vol. 16; no. 11; p. 1193
• Main Authors: Maselli, R A, Wollman, R L, Leung, C, Distad, B, Palombi, S, Richman, D P, Salazar-Grueso, E F, Roos, R P
• Format: Journal Article
• Language: English
• Published: United States 01-11-1993
• Subjects: Acetylcholine - pharmacology; Action Potentials - physiology; Adult; Aged; Amyotrophic Lateral Sclerosis - pathology; Amyotrophic Lateral Sclerosis - physiopathology; Electromyography - instrumentation; Electromyography - methods; Evoked Potentials - physiology; Female; Humans; Magnesium - pharmacology; Male; Membrane Potentials - physiology; Microelectrodes; Middle Aged; Motor Endplate - drug effects; Motor Endplate - metabolism; Motor Endplate - physiopathology; Motor Endplate - ultrastructure; Myofibrils - drug effects; Myofibrils - metabolism; Myofibrils - physiology; Myofibrils - ultrastructure; Neuromuscular Junction - drug effects; Neuromuscular Junction - metabolism; Neuromuscular Junction - physiopathology; Neuromuscular Junction - ultrastructure; Neurotransmitter Agents - metabolism; Synaptic Transmission - physiology
• ISSN: 0148-639X
• DOI: 10.1002/mus.880161109

The functional and structural characteristics of the neuromuscular junction were studied in anconeus muscle biopsies of 10 patients with amyotrophic lateral sclerosis (ALS). Intracellular recordings revealed decreased amplitudes of miniature endplate potentials (MEPPs). The MEPP frequencies were highly variable in ALS patients but the average MEPP frequency was not different from that of control patients. The mean quantal content of endplate potentials (m), the mean quanta available for immediate release (n), and the mean quantal stores (N) were all decreased. In contrast, the mean probability of quantal release (p) was normal and the mean probability of quantal store release (P) was surprisingly high at the majority of ALS endplates. Histologic evidence of denervation and small or absent nerve terminals were observed in all ALS patients. These functional and structural abnormalities of the neuromuscular junction may explain the fatigability and the electromyographic evidence of impaired neuromuscular transmission often encountered in ALS patients.