Abstract
In the present work, stimuli were given to the rootlet of the dorsal root of the L7 spinal cord of cat, and the reflex discharge was induced from other rootlet and recorded. The dorsal root reflex occurs normally. In the dorsal root reflex, no monosynaptic arc is recognized. They are all polysynaptic arcs. The reflex time was shortened as the stimulus became stronger, but it reached the maximum without further shortening when the strength of stimulus reached a certain strength. The minimum reflex time in the present experiment was approximately 7.4 msec.
The reflex discharge was also enhanced as the strength of stimulus became stronger, and it reached the maximum at certain strength. This maximum did not go up any further even with stronger stimulus.
The dorsal root reflex was examined with the stimulation of the Nervus tibialis, but the occurrence of the dorsal root reflex was found weak. No correlation between the strength of the afferent impulse and the strength of the dorsal root reflex was recognized. However, the presence of a small number of afferent fibres participating the dorsal root reflex in Nervus tibialis could not be denied.
Two consecutive stimuli were given to a same rootlet of L7 dorsal root and the reflex discharge was induced from other rootlet. In this case, it was learnt that the excitability of the reflex arc of the dorsal root reflex was lowered due to the first stimulus over a period of 600 msec.
In view of the above facts, the authors confirmed the presence of the dorsal root reflex, and concluded that the dorsal root reflex essentially does not differ from the ordinary so-called ventral root reflex.
