Ultraviolet-B-induced mechanical hyperalgesia: A role for peripheral sensitisation

Item Type:	Article
Title:	Ultraviolet-B-induced mechanical hyperalgesia: A role for peripheral sensitisation
Creators Name:	Bishop, T. and Marchand, F. and Young, A.R. and Lewin, G.R. and McMahon, S.B.
Abstract:	Ultraviolet (UV) induced cutaneous inflammation is emerging as a model of pain with a novel sensory phenotype. A UVB dose of 1000mJ/cm2 produces a highly significant thermal and mechanical hypersensitivity. Here we examined the properties and mechanisms of such hyperalgesia in rats. Significantly, the mechanical hyperalgesia (with approximately 60% change in withdrawal thresholds) was restricted to the lesion site with no changes in mechanical threshold in adjacent non-irradiated skin (i.e. no secondary hypersensitivity), suggesting a peripheral mechanism. Consistent with this, we found that primary mechanical hypersensitivity showed no significant changes after intrathecal treatment with 10mug of the NMDA-receptor antagonist MK-801. Using an in vitro skin-nerve preparation, in the presence and absence of UVB-inflammation, suprathreshold responses to skin displacement stimuli of 6-768mum of 103 peripheral nociceptors were recorded. At the peak of UVB-induced hyperalgesia we observed that mechanical response properties of Adelta-nociceptors recorded from UVB-inflamed skin (n=19) were significantly diminished, by approximately 50%, compared to those recorded from naïve skin (n=13). The mechanical response properties of heat-sensitive C-nociceptors were unchanged while their heat responses were significantly increased, by approximately 75%, in UVB-inflamed (n=26) compared to naïve skin (n=12). Heat-insensitive C-nociceptors, however, demonstrated significantly enhanced (by approximately 60%) response properties to mechanical stimulation in UVB-inflamed (n=21) compared to naïve skin (n=12). Notably alteration in mechanical responses of Adelta- and heat-insensitive C-nociceptors were particular to stronger stimuli. Spontaneous activity was not induced by this dose of UVB. We conclude that UVB-induced mechanical hyperalgesia may be explained by a net shift in peripheral nociceptor response properties.
Keywords:	Hyperalgesia, Nociceptor, Pain, Inflammation, Animals, Rats
Source:	Pain
ISSN:	0304-3959
Publisher:	Elsevier
Volume:	150
Number:	1
Page Range:	141-152
Date:	July 2010
Official Publication:	https://doi.org/10.1016/j.pain.2010.04.018
PubMed:	View item in PubMed

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