Properties of axon terminals contacting intermediate zone excitatory and inhibitory premotor interneurons with monosynaptic input from group I and II muscle afferents

Liu, T.T., Bannatyne, B., Jankowska, E. and Maxwell, D.J. (2010) Properties of axon terminals contacting intermediate zone excitatory and inhibitory premotor interneurons with monosynaptic input from group I and II muscle afferents. Journal of Physiology, 588(21), pp. 4217-4233. (doi:10.1113/jphysiol.2010.192211)

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Abstract

The intermediate zone of the spinal grey matter contains premotor interneurons mediating reflex actions of group I and II muscle afferents. However, limited information is available on how activity of inhibitory versus excitatory interneurons in this population are modulated and how they contribute to motor networks. There were three aims of this study: (1) to characterize excitatory axonal contacts on interneurons; (2) to determine if contact patterns on excitatory and inhibitory interneurons are different; (3) to determine if there are differences in presynaptic inhibitory control of excitatory and inhibitory interneurons. We used intracellular labelling of electrophysiologically identified cells along with immunochemistry to characterise contacts formed by axons that contain vesicular glutamate transporters (VGLUT1 and VGLUT2) and contacts formed by VGLUT1 terminals which in turn were contacted by GABAergic terminals on cells that were characterised according to their transmitter phenotype. All seventeen cells investigated were associated with numerous VGLUT1 contacts originating from primary afferents, and similar contact densities were found on excitatory and inhibitory cells, but VGLUT2-immunoreactive terminals originating form intraspinal neurons were less frequent, or were practically absent, especially on excitatory cells. Similar numbers of VGLUT1 contacts with associated GABAergic terminals were found on excitatory and inhibitory cells indicating a similar extent of presynaptic GABAergic control. However, scarce VGLUT2 terminals on intermediate zone excitatory premotor interneurons with input from muscle afferents suggest that they are not significantly excited by other spinal neurons but are under direct excitatory control of supraspinal neurons and, principally inhibitory, control of spinal neurons.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Bannatyne, Dr Anne and Maxwell, Professor David
Authors: Liu, T.T., Bannatyne, B., Jankowska, E., and Maxwell, D.J.
Subjects:Q Science > QP Physiology
College/School:College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
Research Group:Spinal cord Group
Journal Name:Journal of Physiology
ISSN:0022-3751
ISSN (Online):1469-7793
Published Online:29 October 2010

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
284171Spinal Interneurons: 5HT-NA receptors, actions, circuitsDavid MaxwellNational Institutes of Health (NIHBETH)UNSPECIFIEDInstitute of Neuroscience and Psychology