Repetitive doublet firing of motor units: evidence for plateau potentials in human motoneurones?

摘要: During voluntary muscle contraction, human motoneurones can exhibit specific discharge patterns: single and repetitive doublets. Delayed depolarization has been accepted as the mechanism underlying Repetitive doublet firing studied much less its controlling mechanisms remain obscure. The aim of present study was to examine properties doublets in consider their potential mechanisms. It found that 22 41 (53.7%) lower-threshold motor units (MUs) trapezius 15 42 (35.7%) MUs triceps brachii displayed with mean interspike intervals (ISIs) 5.5 ± 1.1 6.4 2.6 ms, respectively. Each followed by a prolonged post-doublet ISI. analysis showed they were typically initiated quiescent rather than ones (appearing just at recruitment an all-or-none manner) could only be maintained certain level contraction. interrupted either voluntarily (by subject), or spontaneously sudden transition from discharges—the behaviour may referred firing-pattern “jump”. seem consistent traits motoneurone presence plateau potentials reported animal studies. suggested include delayed primary determinant, which likely become persistent probably due activated parallel common synaptic input.