Morphology of inhibitory and excitatory interneurons in superficial laminae of the rat dorsal horn

Maxwell, D.J. , Belle, M.D., Cheunsuang, O., Stewart, A. and Morris, R. (2007) Morphology of inhibitory and excitatory interneurons in superficial laminae of the rat dorsal horn. Journal of Physiology, 584(2), pp. 521-533. (doi: 10.1113/jphysiol.2007.140996)

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If we are to stand any chance of understanding the circuitry of the superficial dorsal horn, it is imperative that we can identify which classes of interneuron are excitatory and which are inhibitory. Our aim was to test the hypothesis that there is a correlation between the morphology of an interneuron and its postsynaptic action. We used in vitro slice preparations of the rat spinal cord to characterize and label interneurons in laminae I–III with Neurobiotin. Labelled cells (n = 19) were reconstructed in 3D with Neurolucida and classified according to the scheme proposed by Grudt & Perl (2002). We determined if cells were inhibitory or excitatory by reacting their axon terminals with antibodies to reveal glutamate decrboxylase (for GABAergic cells) or the vesicular glutamate transporter 2 (for glutamatergic cells). All five islet cells retrieved were inhibitory. Of the six vertical (stalked) cells analysed, four were excitatory and, surprisingly, two were inhibitory. It was noted that these inhibitory cells had axonal projections confined to lamina II whereas excitatory vertical cells projected to lamina I and II. Of the remaining neurons, three were radial cells (2 inhibitory, 1 excitatory), two were antennae cells (1 inhibitory, 1 excitatory), one was an inhibitory central cell and the remaining two were unclassifiable excitatory cells. Our hypothesis appears to be correct only for islet cells. Other classes of cells have mixed actions, and in the case of vertical cells, the axonal projection appears to be a more important determinant of postsynaptic action.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Maxwell, Professor David
Authors: Maxwell, D.J., Belle, M.D., Cheunsuang, O., Stewart, A., and Morris, R.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Journal of Physiology
ISSN (Online):1469-7793
Published Online:23 August 2007

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