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Titolo:
TRISYNAPTIC INHIBITION FROM THE CONTRALATERAL VERTICAL SEMICIRCULAR CANAL NERVES TO NECK MOTONEURONS MEDIATED BY SPINAL COMMISSURAL NEURONS
Autore:
SUGIUCHI Y; IZAWA Y; SHINODA Y;
Indirizzi:
TOKYO MED & DENT UNIV,SCH MED,DEPT PHYSIOL,BUNKYO KU,1-5-45 YUSHIMA TOKYO 113 JAPAN TOKYO MED & DENT UNIV,SCH MED,DEPT PHYSIOL,BUNKYO KU TOKYO 113 JAPAN TOKYO MED & DENT UNIV,SCH MED,DEPT OTOLARYNGOL,BUNKYO KU TOKYO 113 JAPAN
Titolo Testata:
Journal of neurophysiology
fascicolo: 5, volume: 73, anno: 1995,
pagine: 1973 - 1987
SICI:
0022-3077(1995)73:5<1973:TIFTCV>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
CONJUGATED HORSERADISH-PEROXIDASE; AXON COLLATERALS; SPINODELTOIDEUS MOTONEURONS; TRANSNEURONAL TRANSPORT; VESTIBULOSPINAL TRACT; REACTION-PRODUCT; CAT; CORD; INTERNEURONS; CONNECTIONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Physical, Chemical & Earth Sciences
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
61
Recensione:
Indirizzi per estratti:
Citazione:
Y. Sugiuchi et al., "TRISYNAPTIC INHIBITION FROM THE CONTRALATERAL VERTICAL SEMICIRCULAR CANAL NERVES TO NECK MOTONEURONS MEDIATED BY SPINAL COMMISSURAL NEURONS", Journal of neurophysiology, 73(5), 1995, pp. 1973-1987

Abstract

1. Neck motoneurons usually receive disynaptic excitation and inhibition from individual semicircular canal nerves. However, in motoneuronsof some neck muscles, trisynaptic inhibition is evoked by stimulationof the contralateral vertical canal nerves. The present study was performed to analyze this pathway and the location and properties of the last-order interneurons responsible for mediating this trisynaptic inhibition from the contralateral vertical canal nerves to neck motoneurons in anesthetized cats. 2. Bipolar stimulating electrodes were implanted on the contralateral anterior (ACN), lateral (LCN), and posterior canal nerve (PCN), and postsynaptic potentials (PSPs) evoked by electrical stimulation of individual canal nerves were intracellularly recorded from motoneurons of the obliquus capitis inferior (OCI), longus capitis (LC), and rectus capitis posterior (RCP) muscles. Stimulation ofthe contralateral ACN evoked trisynaptic inhibitory PSPs (IPSPs) in OCI and LC motoneurons and disynaptic excitatory PSPs (EPSPs) in RCP motoneurons. Stimulation of the contralateral PCN evoked di- and trisynaptic IPSPs in OCI and RCP motoneurons and disynaptic EPSPs in LC motoneurons. Stimulation of the contralateral LCN evoked disynaptic EPSPs in all of the motoneurons examined. 3. To determine the pathway that mediates these trisynaptic IPSPs from the vertical canal nerves to neck motoneurons, a lesion was made in the lower medulla, and the patterns of PSPs evoked by stimulation of the three contralateral canal nerves were compared before and after the lesion. Interruption of the ipsilateral medial longitudinal fascicle (MLF) abolished all disynaptic EPSPsand IPSPs from the three contralateral canal nerves in OCI, LC, and RCP motoneurons. In contrast, trisynaptic IPSPs evoked by stimulation of the contralateral ACN or PCN remained unaffected by sectioning the MLFs bilaterally. Sectioning of the contralateral lateral vestibulospinal tract (LVST) eliminated the trisynaptic IPSPs in OCI and LC motoneurons evoked by contralateral ACN stimulation and trisynaptic IPSPs in OCI and RCP motoneurons evoked by contralateral PCN stimulation but did not affect disynaptic EPSPs and IPSPs. 4. Stimulation of the contralateral LVST in the lower medulla after sectioning the bilateral MLFs evoked disynaptic IPSPs in OCI, LC, and RCP motoneurons. Because the LVST only projects ipsilaterally, this finding indicates that the last-order interneurons that mediate the trisynaptic inhibition through the LVST are most likely commissural neurons located in the spinal cord. 5. To determine the locations of last-order commissural neurons terminating on OCI motoneurons, wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was injected into the OCI muscle nerve at CI. In addition to retrogradely labeled motoneurons, many neurons were transneuronally labeled mainly in lamina Vm and sparsely in laminae VII and IX of the contralateral ventral hem.6. Spinal commissural neurons receiving disynaptic excitation from the ipsilateral vertical canal nerves through the LVST were penetrated and injected with HRP intra-axonally. These neurons were located in lamina VIII. Stem axons ran dorsomedially and, after crossing the midline, bifurcated into ascending and descending branches. These branches gave rise to multiple axon collaterals that projected to ipsilateral neck motor nuclei. In the motor nuclei, axon terminals of these collaterals appeared to make contact withcell bodies and proximal dendrites of labeled neck motoneurons. 7. Microstimulation of contralateral lamina VIII evoked predominantly monosynaptic IPSPs in OCI, LC, and RCP motoneurons. These monosynaptic IPSPs were facilitated by conditioning stimulation of the contralateral ACN in OCI and LC motoneurons and of the contralateral PCN in OCI and RCP motoneurons. These results show that there are last-order inhibitorycommissural neurons in lamina VIII. The present study has elucidated that trisynaptic inhibition from the contralateral vertical canal nerves is mediated through the contralateral LVST and inhibitory commissural neurons in lamina VIII of the upper cervical cord to OCI, LC, and RCP motoneurons. The trisynaptic connections between the vestibular afferents and neck motoneurons, in addition to the disynaptic connections, may play an important role in the vestibulocollic reflex.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/11/20 alle ore 10:13:53