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Functional organization of spinal nociceptive pathways: evidence for a modular organization of spinal nociceptive reflex systems

Weng, Han-Rong (1996)
Abstract
The functional organization of the hindlimb withdrawal reflex system was studied in the rat. For the reflex pathway to each muscle, a "mirror-image" relationship was found between the spatial distribution of sensitivity within its cutaneous receptive field and the pattern of cutaneous unloading ensuing on muscle contraction. Thus, the withdrawal movement pattern ensuing on contraction in a muscle is "imprinted" on the withdrawal reflex pathways to that muscle. Putative reflex interneurones capable of encoding the reflex strength from the entire receptive field of a reflex pathway were found in the deep dorsal horn of the lumbar segments. These neurones had a topographical organization. The neurones encoding the reflex activity in single... (More)
The functional organization of the hindlimb withdrawal reflex system was studied in the rat. For the reflex pathway to each muscle, a "mirror-image" relationship was found between the spatial distribution of sensitivity within its cutaneous receptive field and the pattern of cutaneous unloading ensuing on muscle contraction. Thus, the withdrawal movement pattern ensuing on contraction in a muscle is "imprinted" on the withdrawal reflex pathways to that muscle. Putative reflex interneurones capable of encoding the reflex strength from the entire receptive field of a reflex pathway were found in the deep dorsal horn of the lumbar segments. These neurones had a topographical organization. The neurones encoding the reflex activity in single muscles were located in restricted areas. The multisensory input to the withdrawal reflex pathways was characterized using a battery of mechanical, thermal and chemical stimuli. The results suggest that withdrawal reflexes receive an excitatory input from slowly adapting mechanoreceptive fibres and from nociceptors, but not from rapidly adapting fibres in the glabrous skin or from cold and warm receptors. It was found that withdrawal reflexes, as well as spontaneous activity, of the lower leg muscles can be inhibited by noxious stimulation of specific skin areas on the plantar surface of the ipsilateral hind paw. The inhibitory strength and size of these fields increased spontaneously during the first 12 h after transection of the spinal cord. These nociceptive inhibitory receptive fields would move towards external stimuli on contraction in the respective muscle, suggesting that this inhibitory system serves to curtail inappropriate movements. It is suggested that the withdrawal reflex system consists essentially of a set of functional modules, either excitatory or inhibitory, and that each module is concerned with the control of a single or a few synergistic, muscle(s). (Less)
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author
opponent
  • Prof Alstermark, Bror, UmeĆ„ Universitet, Sverige
publishing date
type
Thesis
publication status
published
subject
keywords
neurophysiology, neuropsychology, Neurology, electromyography., spinal cord, hyperreflexia, neural plasticity, spinal injuries, receptive fields, inhibitory mechanisms, motor control, flexion reflex, interneurones, Neurologi, sensorimotor integration, somatosensory, analgesia, pain, nociception, neuropsykologi, neurofysiologi
pages
62 pages
publisher
Department of Physiology and Neuroscience, Lund University
defense location
F1, Centralblocket, Universitetssjukhuset, Lund
defense date
1996-09-13 13:00
external identifiers
  • Other:ISRN: LUMEDW/MEFN--1--SE
ISBN
91-628-2128-8
language
English
LU publication?
no
id
5a170aff-c04b-4b14-981c-67af24e5a913 (old id 28632)
date added to LUP
2007-06-12 13:54:49
date last changed
2016-09-19 08:45:05
@misc{5a170aff-c04b-4b14-981c-67af24e5a913,
  abstract     = {The functional organization of the hindlimb withdrawal reflex system was studied in the rat. For the reflex pathway to each muscle, a "mirror-image" relationship was found between the spatial distribution of sensitivity within its cutaneous receptive field and the pattern of cutaneous unloading ensuing on muscle contraction. Thus, the withdrawal movement pattern ensuing on contraction in a muscle is "imprinted" on the withdrawal reflex pathways to that muscle. Putative reflex interneurones capable of encoding the reflex strength from the entire receptive field of a reflex pathway were found in the deep dorsal horn of the lumbar segments. These neurones had a topographical organization. The neurones encoding the reflex activity in single muscles were located in restricted areas. The multisensory input to the withdrawal reflex pathways was characterized using a battery of mechanical, thermal and chemical stimuli. The results suggest that withdrawal reflexes receive an excitatory input from slowly adapting mechanoreceptive fibres and from nociceptors, but not from rapidly adapting fibres in the glabrous skin or from cold and warm receptors. It was found that withdrawal reflexes, as well as spontaneous activity, of the lower leg muscles can be inhibited by noxious stimulation of specific skin areas on the plantar surface of the ipsilateral hind paw. The inhibitory strength and size of these fields increased spontaneously during the first 12 h after transection of the spinal cord. These nociceptive inhibitory receptive fields would move towards external stimuli on contraction in the respective muscle, suggesting that this inhibitory system serves to curtail inappropriate movements. It is suggested that the withdrawal reflex system consists essentially of a set of functional modules, either excitatory or inhibitory, and that each module is concerned with the control of a single or a few synergistic, muscle(s).},
  author       = {Weng, Han-Rong},
  isbn         = {91-628-2128-8},
  keyword      = {neurophysiology,neuropsychology,Neurology,electromyography.,spinal cord,hyperreflexia,neural plasticity,spinal injuries,receptive fields,inhibitory mechanisms,motor control,flexion reflex,interneurones,Neurologi,sensorimotor integration,somatosensory,analgesia,pain,nociception,neuropsykologi,neurofysiologi},
  language     = {eng},
  pages        = {62},
  publisher    = {ARRAY(0x98a3060)},
  title        = {Functional organization of spinal nociceptive pathways: evidence for a modular organization of spinal nociceptive reflex systems},
  year         = {1996},
}