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Complex regional pain syndrome: intradermal injection of phenylephrine evokes pain and hyperalgesia in a subgroup of patients with upregulated α1-adrenoceptors on dermal nerves

Drummond, P.D.ORCID: 0000-0002-3711-8737, Morellini, N., Finch, P.M.ORCID: 0000-0002-2717-054X, Birklein, F. and Knudsen, L.F. (2018) Complex regional pain syndrome: intradermal injection of phenylephrine evokes pain and hyperalgesia in a subgroup of patients with upregulated α1-adrenoceptors on dermal nerves. PAIN, 159 (11). pp. 2296-2305.

Link to Published Version: https://doi.org/10.1097/j.pain.0000000000001335
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Abstract

The aim of this study was to determine whether upregulated cutaneous expression of α1-adrenoceptors (α1-AR) is a source of pain in patients with complex regional pain syndrome (CRPS). Immunohistochemistry was used to identify α1-AR on nerve fibres and other targets in the affected and contralateral skin of 90 patients, and in skin samples from 38 pain-free controls. The distribution of α1-AR was compared between patients and controls, and among subgroups of patients defined by CRPS duration, limb temperature asymmetry, and diagnostic subtype (CRPS I vs CRPS II). In addition, α1-AR expression was investigated in relation to pain and pinprick hyperalgesia evoked by intradermal injection of the α1-AR agonist phenylephrine. Expression of α1-AR on nerve bundles in the CRPS-affected limb was greater in patients who reported prolonged pain and pinprick hyperalgesia around the phenylephrine injection site than in patients with transient pain after the injection. In addition, α1-AR expression in nerve bundles was greater in patients with CRPS II than CRPS I, and was greater in acute than more long-standing CRPS. Although less clearly associated with the nociceptive effects of phenylephrine, α1-AR expression was greater on dermal nerve fibres in the painful than contralateral limb. Together, these findings are consistent with nociceptive involvement of cutaneous α1-AR in CRPS. This involvement may be greater in acute than chronic CRPS, and in CRPS II than CRPS I.

Item Type: Journal Article
Murdoch Affiliation(s): School of Psychology and Exercise Science
Publisher: Wolters Kluwer N.V.
Copyright: © 2018 International Association for the Study of Pain
URI: http://researchrepository.murdoch.edu.au/id/eprint/42435
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