手根関節伸張反射において橈尺関節角度が協働筋反射活動に与える影響

抄録

It is known that in the wrist flexors (the flexor carpi radialis (FCR) and ulnaris (FCU) muscles) the afferent inputs from one muscle project to not only the motoneurons innervating the muscle itself, but also to the motoneurons of its synergist. Consequently, such spinal connections should cause some interaction between the reflex responses of the two synergists. However, it is not clear yet how the central nervous system controls the reflex activity of these synergists. The present study shows that the reflex responses (the amount of EMG activity in each muscle) of wrist synergistic muscles were modulated by the radio-ulnar joint angle, which allows a change of the lengths of FCR and FCU muscles while keeping the wrist joint at a constant angle. This result means that the response of the wrist stretch reflex is produced by using the synergists as the muscle length demands, even when a similar reflex flexion is apparently induced by stretch stimulus from a constant wrist angle. In addition, in both the short and long latency reflexes, two factorial ANOVA revealed significant interaction between muscles (FCR and FCU) and radio-ulnar joint angles. Thus, the supra-spinal system for processing long latency reflex seems to mediate the reflex responses of wrist synergists in a similar fashion to that of the spinal reflex system. [J Physiol Sci. 2008;58 Suppl:S194]