Repetitive discharge due to self-ephaptic excitation of a motor unit.
Repetitive discharges (RDs) of a motor unit action potential were evoked by nerve stimulation in chronically denervated muscles of 3 patients. One RD also occurred at rest and during voluntary contraction. The 3 RDs had a regular firing frequency of respectively 16, 27 and 28.5 c/sec. Double stimulation evoked an RD consisting of doublets. An ectopic discharge arising during the RD had the same effect. These observations make likely that such RDs result from a 1-way ephaptic reverberating excitation occurring within a single MU. The synchronized potential of muscle fibres grouped by reinnervation may re-excite an axonal branch of the same MU, thus initiating a reverberating loop.
Roth
G
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Division of Clinical Neurophysiology, University Hospital, Geneva, Switzerland.
D000200:Action Potentials / Q000502:physiology*; D000368:Aged; D002349:Carpal Tunnel Syndrome / Q000503:physiopathology; D002607:Charcot-Marie-Tooth Disease / Q000503:physiopathology; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009121:Muscle Denervation; D010525:Peripheral Nerves / Q000503:physiopathology