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Pain. 2007 Apr;128(3):199-208. Epub 2006 Nov 7.

Catechol-O-methyltransferase inhibition increases pain sensitivity through activation of both beta2- and beta3-adrenergic receptors.

Author information

1
Center for Neurosensory Disorders, School of Dentistry, University of North Carolina, Chapel Hill, NC 27599-7450, USA. andrea_neely@dentistry.unc.edu <andrea_neely@dentistry.unc.edu>

Abstract

Catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines, has recently been implicated in the modulation of pain. Our group demonstrated that human genetic variants of COMT are predictive for the development of Temporomandibular Joint Disorder (TMJD) and are associated with heightened experimental pain sensitivity [Diatchenko, L, Slade, GD, Nackley, AG, Bhalang, K, Sigurdsson, A, Belfer, I, et al., Genetic basis for individual variations in pain perception and the development of a chronic pain condition, Hum Mol Genet 2005;14:135-43.]. Variants associated with heightened pain sensitivity produce lower COMT activity. Here we report the mechanisms underlying COMT-dependent pain sensitivity. To characterize the means whereby elevated catecholamine levels, resulting from reduced COMT activity, modulate heightened pain sensitivity, we administered a COMT inhibitor to rats and measured behavioral responsiveness to mechanical and thermal stimuli. We show that depressed COMT activity results in enhanced mechanical and thermal pain sensitivity. This phenomenon is completely blocked by the nonselective beta-adrenergic antagonist propranolol or by the combined administration of selective beta(2)- and beta(3)-adrenergic antagonists, while administration of beta(1)-adrenergic, alpha-adrenergic, or dopaminergic receptor antagonists fail to alter COMT-dependent pain sensitivity. These data provide the first direct evidence that low COMT activity leads to increased pain sensitivity via a beta(2/3)-adrenergic mechanism. These findings are of considerable clinical importance, suggesting that pain conditions resulting from low COMT activity and/or elevated catecholamine levels can be treated with pharmacological agents that block both beta(2)- and beta(3)-adrenergic receptors.

PMID:
17084978
PMCID:
PMC1905861
DOI:
10.1016/j.pain.2006.09.022
[Indexed for MEDLINE]
Free PMC Article

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