抄録
Slow muscle responses induced by stimulation of the brain-stem reticular formation, which was confirmed in the previous report to send off spontaneous and specific impulses for the maintenance of the posture, were observed mainly in extensors in toad forelimb.
1. A typical pattern of muscle responses so excited was obtained by the liminal stimulation of appropriate sites in the reticular formation (tectal and bulbar). This was composed of two or more successive slow muscle responses. As the stimulation strength was increased, twitch muscle responses appeared overlapping on the slow responses. However, when the stimulation was submaximal, there was found often an intervening slow response in the silent interval.
2. The latency for the 1st muscle response caused by stimulation of the tegmental reticular formation was 25.7 msec. in the mean, which was always shorter by about 5 msec. than that by the bulbar stimulation. This interesting fact was easily recognizable from that accelerating impulses sent from the bulbar reticular formation were intermediated by the tegmental formation, where the efferent fibres start. Impulses sent from the tegmental formation reached in about 16.5 msec. to the contralateral 3rd spinal ventral horn, from which about 5 msec. was spent to the brachial nerve plexus.
3. Supplementary experiments were carried out briefly on flexors and the gastrocnemius muscle. The reticulum stimulation induced muscle responses in flexors only on the side contralateral to stimulation but in the gastrocnemius bilaterally. However, slow muscle responses were not easily detectable.
4. The time interval between the 1st and the 2nd responses of those muscles was characteristic of the muscle group concerned; e. g., about 100 msec. in forelimb extensors, about 150 msec. in flexors and 110 msec. in the gastrocnemius muscle. It was discussed that these rhythmicities may be due to the property of motoneurons innervating those muscles.
I wish to express my sincere thanks to prof. R. ITO for advice and criticism.
