DRD3 Ser9Gly Polymorphism Related to Thermal Pain Perception and Modulation in Fibromyalgia Syndrome

A study e-published ahead of print in the Journal of Pain has found that genetic polymorphisms of a dopamine receptor appear to influence 2 core features of Fibromyalgia Syndrome.

Experimental studies showed that dopamine influences pain perception in healthy volunteers. Dopamine dysfunctions have been linked to the physiopathology of Fibromyalgia Syndrome (Fibro), which is associated with hyperalgesia and deficient pain inhibition.

In this study, the researchers, from the University of Sherbrooke, Canada, sought to investigate the relationships between catecholamine-related genetic polymorphisms [dopamine-D(3) receptor (DRD3) Ser9Gly and catechol-O-methyltransferase (COMT) Val158Met] and thermal pain measures in healthy subjects and Fibro patients.

Catecholamines are a group of sympathomimetic hormones and neurotransmitters (including dopamine, epinephrine, and norepinephrine) involved in the stress "fight-or-flight" response.

There were 73 participants in the study: 37 Fibro patients and 36 healthy controls.

Thermal pain thresholds (TPTs) were measured using a Peltier thermode.

Inhibitory systems were elicited using a thermal tonic pain stimulation administered before and after activation of the diffuse noxious inhibitory controls (DNIC) by means of a cold-pressor test.

Genetic analyses were performed using polymerase chain reaction. Regression analyses were performed across and within groups.

The researchers found that Fibro was associated with lower TPTs and deficient pain inhibition.

They also found that DRD3 Ser9Gly polymorphism predicted (1) DNIC efficacy across groups and (2) thermal TPTs in Fibro patients.

COMT Val158Met and thermal pain measures were not related.

In conclusion:

"These preliminary results suggest that the DRD3 Ser9Gly polymorphism influences DNIC efficacy and TPTs and that this latter relationship is present only in [Fibromyalgia Syndrome] patients. Two core psychophysical features of [Fibromyalgia Syndrome] appear to be significantly influenced by limbic dopamine functioning."

This experimental study is the first to relate DNIC and TPTs to a functional polymorphism of limbic dopamine-D3 receptors. As lowered pain thresholds and deficient pain inhibition are 2 core features of Fibromyalgia Syndrome, these preliminary results may help identify a subgroup of Fibro patients who require closer medical attention.

References:

1. Potvin S, Larouche A, Normand E, de Souza JB, Gaumond I, Grignon S, Marchand S. DRD3 Ser9Gly Polymorphism Is Related to Thermal Pain Perception and Modulation in Chronic Widespread Pain Patients and Healthy Controls. J Pain. 2009 May 21. [Epub ahead of print]