Partial reversal of conduction slowing during repetitive stimulation of single sympathetic efferents in human skin.
Acta Physiol Scand
; 182(3): 305-11, 2004 Nov.
Article
em En
| MEDLINE
| ID: mdl-15491409
ABSTRACT
AIMS:
To describe and identify the function of a class of human C fibre with an unusual response to repetitive electrical stimulation. Other C fibres slow progressively at 2 Hz (type 1), reach a latency plateau (type 2) or hardly slow at all (type 3).METHODS:
C fibres innervating hairy skin were recorded by microneurography in the superficial peroneal nerves of 19 healthy volunteers. Baseline electrical stimulation of the skin was at 0.25 Hz, and activity-dependent slowing recorded during stimulation at 2 Hz for 3 min and after a 3-min pause in stimulation.RESULTS:
In 41 units, there was a partial recovery of latency during repetitive stimulation. These were classified as 'type-4' units, and identified as sympathetic efferents, since they exhibited spontaneously activity, which was enhanced by manoeuvres that increase sympathetic outflow (15 of 16 cases) and/or suppressed by a proximal anaesthetic block (eight of eight cases). The peak slowing during 2 Hz trains averaged 6.47 +/- 2.06% (mean +/- SD, n=41), but after 3 min the slowing had reduced to 4.90 +/- 2.20%, which was less than in all type 1 (nociceptor) fibres but similar to that in type 2 (cold) fibres. Compared with cold fibres, type-4 sympathetic fibres slowed more after the first 10 impulses at 2 Hz (2.57 +/- 0.45%) and also after a pause in stimulation (1.66 +/- 0.51%).CONCLUSIONS:
The distinctive activity-dependent slowing profiles of these type-4 sympathetic C units may help identification in vitro, and suggest that hyperpolarization-activated channels have a particularly prominent role in the axonal membrane.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fenômenos Fisiológicos da Pele
/
Sistema Nervoso Simpático
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Fibras Nervosas Amielínicas
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Condução Nervosa
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Neurônios Eferentes
Limite:
Adolescent
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Adult
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Female
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Humans
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Male
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Middle aged
Idioma:
En
Revista:
Acta Physiol Scand
Ano de publicação:
2004
Tipo de documento:
Article