Research Article

You have full text access to this OnlineOpen article

Axon diversity of lamina I local-circuit neurons in the lumbar spinal cord

  1. Peter Szucs1,†,*,
  2. Liliana L. Luz1,
  3. Raquel Pinho1,
  4. Paulo Aguiar1,2,
  5. Zsófia Antal3,
  6. Sheena Y.X. Tiong4,
  7. Andrew J. Todd4,
  8. Boris V. Safronov1

DOI: 10.1002/cne.23311

Additional Information

Author Information

  1. 1

    Spinal Neuronal Networks Group, Institute of Molecular and Cell Biology - IBMC, University of Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal

  2. 2

    Faculty of Sciences, Department of Applied Mathematics, Center of Mathematics of the University of Porto - CMUP, Porto, Portugal

  3. 3

    Department of Anatomy, Histology and Embryology, University of Debrecen, Medical and Health Science Centre, Nagyerdei krt. 98, 4032 Debrecen, Hungary

  4. 4

    Spinal Cord Group, College of Medical Veterinary and Life Sciences, University of Glasgow, University Avenue, G12 8QQ Glasgow, UK

  1. †

    phone: +351-22-6074972 fax: +351-22-6099157

*Institute of Molecular and Cell Biology - IBMC, University of Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal

  1. †

    phone: +351-22-6074972 fax: +351-22-6099157

Publication History

  1. Accepted manuscript online: 5 FEB 2013 08:36AM EST
  2. Manuscript Accepted: 18 JAN 2013
  3. Manuscript Revised: 11 JAN 2013
  4. Manuscript Received: 31 OCT 2012

Funded by

  • Portuguese Foundation for Science and Technology funded. Grant Number: POCTI2010
  • FCT. Grant Numbers: Ciência-2007, POPH-QREN

SEARCH

SEARCH BY CITATION

ARTICLE TOOLS

Get PDF (6364K)

Keywords:

  • Interneuron;
  • propriospinal connection;
  • varicosity distribution;
  • propagation time;
  • 3-D reconstruction

Abstract

Spinal lamina I is a key area for relaying and integrating information from nociceptive primary afferents with various other sources of inputs. While lamina I projection neurons have been intensively studied, much less attention has been given to local-circuit neurons (LCNs), which form the majority of the lamina I neuronal population. In this work the infrared light-emitting diode (IR-LED) oblique illumination technique was used to visualize and label LCNs, allowing reconstruction and analysis of their dendritic and extensive axonal trees.

We show that the majority of lamina I neurons with locally branching axons fall into the multipolar (with ventrally protruding dendrites) and flattened (dendrites limited to lamina I) somatodendritic categories. Analysis of their axons revealed that the initial myelinated part gives rise to several unmyelinated small-diameter branches that have a high number of densely packed large varicosities and an extensive rostrocaudal (2-3 segments), mediolateral and dorsoventral (reaching laminae III-IV) distribution. The extent of the axon and the occasional presence of long solitary branches suggest that LCNs may also form short and long propriospinal connections. We also found that the distribution of axon varicosities and terminal field locations show substantial heterogeneity and that a substantial portion of LCNs is inhibitory.

Our observations indicate that LCNs of lamina I form intersegmental as well as interlaminar connections and may govern large numbers of neurons, providing anatomical substrate for rostrocaudal “processing units” in the dorsal horn. J. Comp. Neurol., 2013. © 2013 Wiley Periodicals, Inc.

Get PDF (6364K)