Summary
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1.
The effect of stimulation of the red nucleus on lumbosacral motoneurones was investigated in cats with conditioning of monosynaptic test reflexes and intracellular recording.
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2.
Experimental procedures were adopted to assure that the effect of stimulation was mediated by the rubrospinal tract.
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3.
Excitation of flexor and inhibition of extensor motoneurones is common but a mixture of EPSPs and IPSPs is found in many motoneurones. In some extensor (particularly toe extensor) motor nuclei there is dominating excitation.
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4.
Differential effects are found in motor nuclei innervating fast and slow muscles, excitation being more prevalent in the former and inhibition in the latter.
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5.
For both EPSPs and IPSPs the minimal synaptic linkage is disynaptic but in one exceptional case a monosynaptic EPSP was observed.
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6.
The results are discussed in relation to other findings regarding the interneuronal organization in the spinal cord.
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This is the first of a series of four papers. The remaining papers describe rubrospinal effects on: interneuronal transmission in reflex paths (II), primary afferent terminals (III), interneurones (IV).
This work has been supported by the Swedish Medical Research Council (Projects No. 14X-94-03B and 14X-94-04C).
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Hongo, T., Jankowska, E. & Lundberg, A. The rubrospinal tract. I. Effects on alpha-motoneurones innervating hindlimb muscles in cats. Exp Brain Res 7, 344–364 (1969). https://doi.org/10.1007/BF00237320
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DOI: https://doi.org/10.1007/BF00237320