Activity‐dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin

Serra, Jordi; Campero, Mario; Ochoa, José L.; Bostock, Hugh

doi:10.1111/j.1469-7793.1999.799ab.x

Cited by 189 publications

(229 citation statements)

References 24 publications

(47 reference statements)

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“…Intermittent failure patterns similar to the described in our paper are more investigated in C-type unmyelinated fibres, for example, see [43,44]. It must be noted that in the case of C-type fibres, the failure appears at rather low frequencies (4 Hz), whereas in our model of the myelinated fibre the failure appears at higher frequencies (greater than 100 Hz).…”

Section: Discussionmentioning

confidence: 89%

Excitation block in a nerve fibre model owing to potassium-dependent changes in myelin resistance

et al. 2010

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The myelinated nerve fibre is formed by an axon and Schwann cells or oligodendrocytes that sheath the axon by winding around it in tight myelin layers. Repetitive stimulation of a fibre is known to result in accumulation of extracellular potassium ions, especially between the axon and the myelin. Uptake of potassium leads to Schwann cell swelling and myelin restructuring that impacts the electrical properties of the myelin. In order to further understand the dynamic interaction that takes place between the myelin and the axon, we have modelled submyelin potassium accumulation and related changes in myelin resistance during prolonged high-frequency stimulation. We predict that potassium-mediated decrease in myelin resistance leads to a functional excitation block with various patterns of altered spike trains. The patterns are found to depend on stimulation frequency and amplitude and to range from no block (less than 100 Hz) to a complete block (greater than 500 Hz). The transitional patterns include intermittent periodic block with interleaved spiking and non-spiking intervals of different relative duration as well as an unstable regime with chaotic switching between the spiking and non-spiking states. Intermittent conduction blocks are accompanied by oscillations of extracellular potassium. The mechanism of conductance block based on myelin restructuring complements the already known and modelled block via hyperpolarization mediated by the axonal sodium pump and potassium depolarization.

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Section: Discussionmentioning

confidence: 89%

Excitation block in a nerve fibre model owing to potassium-dependent changes in myelin resistance

et al. 2010

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“…They are probably characteristic for the hairy skin in other parts of the limbs. C-cold units are rare compared with nociceptors (Serra et al, 1999) and have electrical thresholds that are lower or in the same range as CMH. Although A␦ units were not as systematically studied as C-fibers, their electrical thresholds were always lower than those of CM i and usually also lower than those of CMH (our unpublished observations).…”

Section: Discussionmentioning

confidence: 99%

Brain Activation during Input from Mechanoinsensitive versus Polymodal C-Nociceptors

Ruehle¹,

Handwerker²,

Lennerz³

et al. 2006

J. Neurosci.

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C-nociceptors mediating cutaneous pain in humans can be distinguished in mechano-heat-responsive units (CMH) and mechanoinsensitive units (CM i ). However, if sensitized in damaged tissue, CM i play an important role in inflammatory pain. CM i differ from CMH by higher electrical thresholds and by mediating the axon reflex. Using these properties, we established two stimulation paradigms: (1) transcutaneous stimulation (TCS) of low current density below the CM i threshold and (2) intracutaneous stimulation (ICS) of high current density that excites CM i . This was proven by the quantification of the axon-reflex flare. Applying these stimulation paradigms during functional magnetic resonance imaging, we investigated whether nociceptor stimulation that recruits CM i leads to different cerebral activation than stimuli that do not recruit CM i . Brain activation by CM i was inferred by subtraction. Both stimuli recruited multiple afferents other than CM i , and we expected a common network of regions involved in different aspects of pain perception and motor nocifensive reactions in both stimuli. ICS that additionally recruited CM i should activate regions with low acuity that are involved in pain memory and emotional attribution. Besides a common network of pain in both stimuli, TCS activated the supplementary motor area, motor thalamic nuclei, the ipsilateral insula, and the medial cingulate cortex. These regions contribute to a pain processing loop that coordinates the nocifensive motor reaction. CM i nociceptor activation did not cause relevant activation in this loop and does not seem to play a role in withdrawal. The posterior cingulate cortex was selectively activated by ICS and is apparently important for the processing of inflammatory pain.

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“…Los estudios fisiológicos han permitido inferir el tipo de receptor a partir de las propiedades bioeléctricas del axón: fibras que demuestran un marcado enlentecimiento asociado a la actividad corresponden a nociceptores, mientras que aquellos que se enlentecen en forma moderada son termoreceptores o fibras simpáticas eferentes, mientras los que se enlentecen en forma muy discreta son probablemente mecanoreceptores de bajo umbral. Gracias al conocimiento de estas características ha sido posible detectar la presencia de actividad anormal en aferentes amielínicos [7][8][9]11,23 . En el presente estudio se reconoce actividad anormal en cerca de 50% de las unidades aferentes registradas en cada paciente, lo que contrasta con un hallazgo altamente infrecuente en sujetos normales 9,24 .…”

Section: Discussionunclassified

“…Gracias al conocimiento de estas características ha sido posible detectar la presencia de actividad anormal en aferentes amielínicos [7][8][9]11,23 . En el presente estudio se reconoce actividad anormal en cerca de 50% de las unidades aferentes registradas en cada paciente, lo que contrasta con un hallazgo altamente infrecuente en sujetos normales 9,24 . El correlato clínico de actividad espontánea de nociceptores es, con toda probabilidad, el dolor espontaneo y/o prurito 10,20 mediado por la propagación ortodrómica del potencial de acción hacia el sistema nervioso central, y por otro lado, la inflamación neurogénica -eritralgia-con la invasión antidrómica de potenciales de acción en los terminales de nociceptores cutáneos, particularmente aquellos con las características de nociceptores silentes 25,26 .…”

Section: Discussionunclassified

Actividad espontánea de nociceptores cutáneos en pacientes con neuropatía de fibras delgadas

Campero

2012

Rev. méd. Chile

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Activity‐dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin

Cited by 189 publications

References 24 publications

Excitation block in a nerve fibre model owing to potassium-dependent changes in myelin resistance

Excitation block in a nerve fibre model owing to potassium-dependent changes in myelin resistance

Brain Activation during Input from Mechanoinsensitive versus Polymodal C-Nociceptors

Actividad espontánea de nociceptores cutáneos en pacientes con neuropatía de fibras delgadas

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