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Temperature dependence of excitability indices of human cutaneous afferents
Author(s) -
Burke David,
Mogyoros Ilona,
Vagg Rebecca,
Kiernan Matthew C.
Publication year - 1999
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(199901)22:1<51::aid-mus9>3.0.co;2-q
Subject(s) - refractory period , rheobase , conditioning , interstimulus interval , chemistry , electrophysiology , anesthesia , medicine , mathematics , stimulation , statistics
The temperature dependence of different indices of axonal excitability (threshold, latency, refractoriness, supernormality, strength–duration time constant, and rheobase) was studied for cutaneous afferents of 8 healthy human volunteers using threshold tracking. Cooling from ∼32–∼22°C dramatically increased the threshold for a conditioned potential evoked during the relatively refractory period (average increase 573%) but had little effect on the threshold for unconditioned potentials (increased by 4% with 0.1‐ms test stimuli), strength–duration time constant (increased by 18%), or rheobase (decreased by 12%). Cooling increased the latency of the unconditioned test potential by 41%, but this slowing was small compared with the effect of cooling on the latency slowing attributable to refractoriness. This measure of refractoriness was initially 0.17 ms at a conditioning–test interval of 2 ms, and increased with cooling to 1.30 ms at the same interval. With cooling, refractoriness was both greater at any one conditioning–test interval and longer in duration, extending into intervals normally associated with supernormality. It is concluded that, although cooling affects all excitability indices to some extent, the most prominent feature is the increase in refractoriness. By contrast, strength–duration time constant is influenced little by temperature. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 51–60, 1999