科研之友
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摘要
Persistent inward current (PIC) plays an important role in setting the input-output gain of motoneurons. In humans, these currents are estimated by calculating the difference between synaptic input at motor unit recruitment and derecruitment (Delta F) derived from paired motor unit recordings. The primary objective of this study was to use the relationship between reciprocal inhibition (RI) and PIC to estimate the contribution of PIC relative to other motoneuron properties that result in nonlinear motor unit firing behavior. This study also assessed the contribution of other intrinsic properties (spike threshold accommodation and spike frequency adaptation) to Delta F estimates of PIC in human motor units by using ramps with varying rates of rise and duration. It was hypothesized that slower rates of ramp rise and longer ramp durations would inflate Delta F estimates of PIC, and RI and PIC values would only be correlated during the ramp with the fastest rate of rise and shortest duration when spike threshold accommodation and spike frequency adaptation is minimized. Fourteen university-aged participants took part in this study. Paired motor unit recordings were made from the right soleus muscle during ramp contractions of plantar flexors with three different rates of rise and durations. Delta F estimates of PIC increased with decreased rates of ramp rise (P %26lt; 0.01) and increased ramp durations (P %26lt; 0.01), most likely due to spike frequency adaptation. A correlation (r = 0.41; P %26lt; 0.03) between Delta F and RI provides evidence that PIC is the primary contributor to Delta F in shorter ramps with faster rates of rise.
- 出版日期2014-5
