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Are crossed actions of reticulospinal and vestibulospinal neurons on feline motoneurons mediated by the same or separate commissural neurons?

Artikel i vetenskaplig tidskrift
Författare Piotr Krutki
Elzbieta Jankowska
Stephen A Edgley
Publicerad i The Journal of neuroscience : the official journal of the Society for Neuroscience
Volym 23
Nummer/häfte 22
Sidor 8041-50
ISSN 1529-2401
Publiceringsår 2003
Publicerad vid Institutionen för fysiologi och farmakologi
Sidor 8041-50
Språk en
Länkar www.ncbi.nlm.nih.gov/entrez/query.f...
Ämnesord Animals, Cats, Efferent Pathways, physiology, Electric Stimulation, Electrodes, Implanted, Excitatory Postsynaptic Potentials, physiology, Hindlimb, Interneurons, physiology, Medulla Oblongata, physiology, Motor Neurons, physiology, Muscle, Skeletal, innervation, physiology, Reticular Formation, physiology, Spinal Cord, cytology, physiology, Vestibular Nucleus, Lateral, physiology
Ämneskategorier Fysiologi

Sammanfattning

Both reticulo- and vestibulospinal neurons coordinate the activity of ipsilateral and contralateral limb muscles. The aim of this study was to investigate whether their actions on contralateral motoneurons are mediated via common interneurons. Two series of experiments were made on deeply anesthetized cats. First, the effects of stimuli applied within the lateral vestibular nucleus and to reticulospinal tract fibers within or close to the medial longitudinal fascicle in the medulla were tested on midlumbar commissural interneurons that projected to contralateral motor nuclei. EPSPs of vestibular origin were found in 16 of 20 (80%) of the interneurons, all of which were excited monosynaptically by reticulospinal fibers. These EPSPs were evoked either monosynaptically or disynaptically. Second, the effects of stimuli applied at the same two locations were tested on contralateral motoneurons, selecting motoneurons in which large disynaptic EPSPs or IPSPs were evoked by reticulospinal fibers. When stimuli that were too weak to evoke any PSPs by themselves were applied together, similar EPSPs or IPSPs were evoked in all 26 motoneurons that were tested, indicating that spatial facilitation occurred premotoneuronally. Facilitation was strongest at those intervals optimal for summation of monosynaptic and/or disynaptic EPSPs evoked in commissural neurons by the earliest reticulospinal and vestibulospinal volleys. The same interneurons thus may be used by reticulospinal and vestibulospinal neurons to influence the activity of contralateral hindlimb muscles. Separate modulation of commands from these two descending neuronal systems may occur at the level of the interneurons that mediate disynaptic excitation of commissural neurons by reticulospinal and vestibulospinal neurons, thereby increasing their flexibility.

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