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Neuronal basis of crossed actions from the reticular formation on feline hindlimb motoneurons.

Artikel i vetenskaplig tidskrift
Författare Elzbieta Jankowska
Ingela Hammar
Urszula Slawinska
Katarzyna Maleszak
Stephen A Edgley
Publicerad i The Journal of neuroscience : the official journal of the Society for Neuroscience
Volym 23
Nummer/häfte 5
Sidor 1867-78
ISSN 1529-2401
Publiceringsår 2003
Publicerad vid Institutionen för fysiologi och farmakologi
Sidor 1867-78
Språk en
Länkar www.ncbi.nlm.nih.gov/entrez/query.f...
Ämnesord Animals, Cats, Efferent Pathways, physiology, Electric Stimulation, methods, Electrodes, Implanted, Evoked Potentials, physiology, Excitatory Postsynaptic Potentials, physiology, Female, Functional Laterality, physiology, Hindlimb, innervation, physiology, Interneurons, physiology, Lumbosacral Region, Male, Motor Neurons, physiology, Neural Inhibition, physiology, Neurons, physiology, Reaction Time, physiology, Reticular Formation, physiology
Ämneskategorier Neurofysiologi

Sammanfattning

Pathways through which reticulospinal neurons can influence contralateral limb movements were investigated by recording from motoneurons innervating hindlimb muscles. Reticulospinal tract fibers were stimulated within the brainstem or in the lateral funiculus of the thoracic spinal cord contralateral to the motoneurons. Effects evoked by ipsilaterally descending reticulospinal tract fibers were eliminated by a spinal hemisection at an upper lumbar level. Stimuli applied in the brainstem evoked EPSPs, IPSPs, or both at latencies of 1.42 +/- 0.03 and 1.53 +/- 0.04 msec, respectively, from the first components of the descending volleys and with properties indicating a disynaptic linkage, in most contralateral motoneurons: EPSPs in 76% and IPSPs in 26%. EPSPs with characteristics of monosynaptically evoked responses, attributable to direct actions of crossed axon collaterals of reticulospinal fibers, were found in a small proportion of the motoneurons, whether evoked from the brainstem (9%) or from the thoracic cord (12.5%). Commissural neurons, which might mediate the crossed disynaptic actions (i.e., were antidromically activated from contralateral motor nuclei and monosynaptically excited from the ipsilateral reticular formation), were found in Rexed's lamina VIII in the midlumbar segments (L3-L5). The results reveal that although direct actions of reticulospinal fibers are much more potent on ipsilateral motoneurons, interneuronally mediated actions are as potent contralaterally as ipsilaterally, and midlumbar commissural neurons are likely to contribute to them. They indicate a close coupling between the spinal interneuronal systems used by the reticulospinal neurons to coordinate muscle contractions ipsilaterally and contralaterally.

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