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This Article Full Text Full Text (PDF) All Versions of this Article: 584/2/521    most recent jphysiol.2007.140996v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Maxwell, D. J. Articles by Morris, R. Search for Related Content PubMed PubMed Citation Articles by Maxwell, D. J. Articles by Morris, R. Related Collections Neuroscience

¹ Spinal Cord Group, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
² Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool L69 7ZJ, UK
³ Department of Veterinary Anatomy, Chulalongkorn University, Bangkok, Thailand
⁴ Renovo Group plc, Manchester Incubator Building, 48 Grafton Street, Manchester M13 9XX, UK

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.

(Received 19 July 2007; accepted after revision 20 August 2007; first published online 23 August 2007)
Corresponding author D. Maxwell: Spinal Cord Group, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK. Email: david.maxwell{at}bio.gla.ac.uk

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