Get access

Membrane Characteristics and Synaptic Responsiveness of Superficial Dorsal Horn Neurons in a Slice Preparation of Adult Rat Spinal Cord

Authors

  • Alex M. Thomson,

    1. Department of Physiology, University College, Cardiff CF1 1XL, UK
    Search for more papers by this author
    • *

      Department of Physiology, Royal Free Hospital School of Medicine, Rowland Hill Street, London NW3 2PF, UK

  • David C. West,

    1. Department of Physiology, University College, Cardiff CF1 1XL, UK
    Search for more papers by this author
    • *

      Department of Physiology, Royal Free Hospital School of Medicine, Rowland Hill Street, London NW3 2PF, UK

  • P. Max Headley

    Corresponding author
    1. Department of Physiology, The Medical School, University of Bristol, Bristol BS8 1TD, UK
      Correspondence to: P. M. Headley, Department of Physiology, The Medical School, University Walk, Bristol BS8 1TD, UK
    Search for more papers by this author

Correspondence to: P. M. Headley, Department of Physiology, The Medical School, University Walk, Bristol BS8 1TD, UK

Abstract

Intracellular recordings have been made from neurons of the superficial dorsal horn in slices of the lumbar and thoracic spinal cord of young adult rats. Three broad categories of neurons could be distinguished on the basis of their firing patterns to intracellular current pulses and their afterhyperpolarizations (AHP); there was no detectable difference in the regional distribution of the three types. Category 1 cells were characterized by maintained firing to intracellular depolarizing current pulses, brief action potential durations and polyphasic AHPs. Category 2 cells showed spike adaptation, without spike attenuation, during intracellular current pulses, and had monophasic AHPs. Category 3 cells fired only 1 or 2 spikes to maintained depolarizing pulses and had smaller monophasic AHPs than category 2 neurons. Spontaneous excitatory and inhibitory postsynaptic potential (epsp and ipsp) activity was seen with psp durations varying widely. Low intensity electrical stimulation of afferent fibres, or of superficial white matter, resulted in polyphasic epsps and/or ipsps. The spike discharge in response to such afferent inputs correlated with the membrane properties of the cells, such that the synaptic responses of category 1 neurons were usually bursts of spikes, whereas category 2 and 3 neurons either failed to fire or fired only a single spike. These results in adult rat spinal cord suggest that the discharge pattern within synaptic sensory responses of superficial dorsal horn neurons is determined by postsynaptic membrane properties as well as by the pattern of the afferent input.

Get access to the full text of this article

Ancillary