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Commissural interneurons with input from group I and II muscle afferents in feline lumbar segments: neurotransmitters, projections and target cells

Journal article
Authors Elzbieta Jankowska
B A Bannatyne
Katinka Stecina
Ingela Hammar
Anna Cabaj
D J Maxwell
Published in Journal of physiology
Volume 587
Issue Pt 2
Pages 401-18
ISSN 1469-7793
Publication year 2009
Published at Institute of Neuroscience and Physiology, Department of Physiology
Pages 401-18
Language en
Links dx.doi.org/10.1113/jphysiol.2008.15...
https://gup.ub.gu.se/file/140988
Keywords Afferent Pathways, cytology, physiology, Animals, Carrier Proteins, metabolism, Cats, Electric Stimulation, Excitatory Postsynaptic Potentials, physiology, Glutamate Decarboxylase, metabolism, Inhibitory Postsynaptic Potentials, physiology, Interneurons, cytology, metabolism, physiology, Medulla Oblongata, physiology, Membrane Proteins, metabolism, Motor Neurons, cytology, metabolism, physiology, Muscle, Skeletal, innervation, Neurotransmitter Agents, metabolism, Reflex, physiology, Spinal Cord, cytology, Vesicular Glutamate Transport Protein 2, metabolism
Subject categories Physiology

Abstract

The aim of this study was to analyse neurotransmitter content, projection areas and target cells of commissural interneurons with input from group I and/or II muscle afferents in lumbar segments in the cat. Axonal projections of 15 intracellularly labelled commissural interneurons were reconstructed. Ten interneurons (nine located in laminae VI-VII, one in lamina VIII) were glutamatergic; only one interneuron (located in lamina VIII) was glycinergic. Contralateral terminal projections were found both in motor nuclei and within laminae VI-VIII. In order to identify target cells of commissural interneurons, effects of stimulation of contralateral group I and II muscle afferents were investigated on interneurons within these laminae. Three tests were used: intracellular records from individual interneurons, modulation of probability of activation of extracellularly recorded interneurons and modulation of their actions on motoneurons using disynaptic PSPs evoked in motoneurons as a measure. All these tests revealed much more frequent and/or stronger excitatory actions of contralateral afferents. The results indicate that commissural interneurons with input from contralateral group I and II afferents target premotor interneurons in disynaptic pathways from ipsilateral group I and II afferents and that excitatory disynaptic actions of contralateral afferents on these interneurons are mediated primarily by intermediate zone commissural interneurons. A second group of commissural interneurons activated by reticulospinal neurons, previously described, frequently had similar, but occasionally opposing, actions to the cells described here, thus indicating that these two subpopulations may act on the same premotor interneurons and either mutually enhance or counteract each other's actions.

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