Morita H, Petersen N, Christensen L O, Sinkjaer T, Nielsen J
Physiologisches Institut, Christian-Albrechts Universität zu Kiel, 24098 Kiel, Germany.
J Neurophysiol. 1998 Aug;80(2):610-20. doi: 10.1152/jn.1998.80.2.610.
The sensitivity of soleus H-reflexes, T-reflexes, and short-latency stretch reflexes (M1) to presynaptic inhibition evoked by a weak tap applied to the biceps femoris tendon or stimulation of the common peroneal nerve (CPN) was compared in 17 healthy human subjects. The H-reflex was strongly depressed for a period lasting up to 300-400 ms (depression to 48 +/- 23%, mean +/- SD, of control at a conditioning test interval of 70 ms) by the biceps femoris tendon tap. In contrast, the short-latency soleus stretch reflex elicited by a quick passive dorsiflexion of the ankle joint was not depressed. The soleus T-reflex elicited by an Achilles tendon tap was only weakly depressed (92 +/- 8%). The H-reflex was also significantly more depressed than the T-reflex at long intervals (>15 ms) after stimulation of CPN (H-reflex 63 +/- 14%, T-reflex 91 +/- 13%; P < 0. 01). However, the short-latency (2 ms) disynaptic reciprocal Ia inhibition evoked by stimulation of CPN was equally strong for H- and T-reflexes (H-reflex 72 +/- 10%, T-reflex 67 +/- 13%; P = 0.07). Peaks in the poststimulus time histogram (PSTH) of the discharge probability of single soleus motor units (n = 53) elicited by an Achilles tendon tap had a longer duration than peaks evoked by electrical stimulation of the tibial nerve (on average 5.0 ms as compared with 2.7 ms). All parts of the electrically evoked peaks were depressed by the conditioning biceps femoris tendon tap (average depression to 55 +/- 27% of control; P < 0.001). A similar depression was observed for the initial 2 ms of the peaks evoked by the Achilles tendon tap (69 +/- 48%; P < 0.001), but the last 2 ms were not depressed. Conditioning stimulation of the CPN at long intervals (>15 ms) also depressed all parts of the electrically evoked PSTH peaks (n = 34; average 65%; P < 0.001) but had only a significant effect on the initial 2 ms of the peaks evoked by the Achilles tendon tap (85%; P < 0.001). We suggest that the different sensitivity of mechanically and electrically evoked reflexes to presynaptic inhibition is caused by a difference in the shape and composition of the excitatory postsynaptic potentials underlying the two reflexes. This difference may be explained by a different composition and/or temporal dispersion of the afferent volleys evoked by electrical and mechanical stimuli. We conclude that it is not straightforward to predict the modulation of stretch reflexes based on observations of H-reflex modulation.
在17名健康人体受试者中，比较了比目鱼肌H反射、T反射和短潜伏期牵张反射（M1）对轻敲股二头肌肌腱或刺激腓总神经（CPN）所诱发的突触前抑制的敏感性。轻敲股二头肌肌腱可使H反射在长达300 - 400毫秒的时间段内受到强烈抑制（在70毫秒的条件测试间隔下，抑制至对照值的48±23%，均值±标准差）。相比之下，踝关节快速被动背屈所诱发的比目鱼肌短潜伏期牵张反射未受抑制。跟腱轻敲所诱发的比目鱼肌T反射仅受到微弱抑制（92±8%）。刺激CPN后较长间隔（>15毫秒）时，H反射也比T反射受到更显著的抑制（H反射63±14%，T反射91±13%；P<0.01）。然而，刺激CPN所诱发的短潜伏期（2毫秒）双突触交互性Ia抑制对H反射和T反射的作用强度相当（H反射72±10%，T反射67±13%；P = 0.07）。跟腱轻敲诱发的比目鱼肌单运动单位（n = 53）放电概率的刺激后时间直方图（PSTH）中的峰值持续时间比胫神经电刺激诱发的峰值更长（平均5.0毫秒，而电刺激为2.7毫秒）。条件性股二头肌肌腱轻敲使电诱发峰值的所有部分均受到抑制（平均抑制至对照值的55±27%；P<0.001）。跟腱轻敲诱发的峰值最初2毫秒也观察到类似的抑制（69±48%；P<0.001），但最后2毫秒未受抑制。较长间隔（>15毫秒）刺激CPN也使电诱发PSTH峰值的所有部分受到抑制（n = 34；平均65%；P<0.001），但仅对跟腱轻敲诱发峰值的最初2毫秒有显著影响（85%；P<0.001）。我们认为，机械性和电诱发反射对突触前抑制的不同敏感性是由两种反射基础的兴奋性突触后电位的形状和组成差异所致。这种差异可能由电刺激和机械刺激所诱发的传入冲动的不同组成和/或时间离散来解释。我们得出结论，基于H反射调制的观察结果来预测牵张反射的调制并非易事。
