THE EFFECT OF MIDBRAIN STIMULATION UPON ALPHA MOTONEURONS IN LUMBAR SPINAL CORD OF THE CAT
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- SASAKI KAZUO
- Department of Physiology, Faculty of Medicine, Kyoto University
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- NAMIKAWA AKIRA
- Department of Physiology, Faculty of Medicine, Kyoto University
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- HASHIRAMOTO SHUNJI
- Department of Physiology, Faculty of Medicine, Kyoto University
Description
1. The effect of stimulation of the midbrain upon the spinal motor activity was investigated by recording intracellular potentials from the spinal alpha motoneurons in lumbar segments of the cat. Indirect effects through the gamma fibers and spindle afferents were excluded by sectioning the ventral roots and the peroneal and tibial nerves.<BR>2. The stimulation of the red nucleus produced EPSP's and consequent spike potential in the contralateral flexor motoneurons with a latency of 9 msec. and IPSP's in the contralateral extensor motoneurons with a latency of 11 msec.<BR>3. The effect of stimulation of the decussations in the midbrain was similar to that of the rubrospinal tracts. It occurred bilaterally with latencies much shorter than from the red nucleus.<BR>4. With the stimulation of the midbrain reticular formation, EPSP's and consequent spike potentials were recorded bilaterally from both flexor and extensor motoneurons with a latency of 6 msec. EPSP's in the extensor motoneurons were followed by slight IPSP's.<BR>5. The central gray matter produced inconspicuous effects upon the spinal motoneurons. They partly resembled those of the reticular formation, the inhibitory effect being somewhat predominant.<BR>6. The midbrain foci facilitated or inhibited the reflex firing of motoneurons as a result of algebraic summation of EPSP or IPSP centrally induced with EPSP induced from the dorsal root.<BR>7. Some spinal interneurons were found responsive to the stimuli delivered to all of the midbrain foci and a dorsal root.<BR>8. The stimulation of the midbrain foci brought about the ventral root slow potentials, which corresponded to the PSP's in single motoneurons and also to the facilitatory or inhibitory effects of the midbrain foci upon the monosynaptic spinal reflexes.We are indebted to Prof. T. Otani for advice and criticism
Journal
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- The Japanese Journal of Physiology
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The Japanese Journal of Physiology 10 (3), 303-316, 1960
THE PHYSIOLOGICAL SOCIETY OF JAPAN
