Relation of dopamine receptor 2 binding to pain perception in female fibromyalgia patients with and without depression--A [¹¹C] raclopride PET-study

Dopamine D2/D3 receptor availability at rest and its association with individual pain perception was investigated using the [(11)C] raclopride PET-method in 24 female Fibromyalgia (FMS) participants with (FMS+, N=11) and without (FMS-, N=13) comorbid depression and in 17 healthy women. Thermal pain thresholds (TPT) and pain responses were assessed outside the scanner. We compared the discriminative capacity, i.e. the individual׳s capacity to discriminate between lower and higher pain intensities and the response criterion, i.e. the subject׳s tendency to report pain during noxious stimulation due to psychological factors. [(11)C] raclopride binding potential (BP), defined as the ratio of specifically bound non-displaceable radioligand at equilibrium (BP(ND)) was used as measure of D2/D3 receptor availability. We found significant group effects of BP(ND) in striatal regions (left ventral striatum, left caudate nucleus and left nucleus accumbens) between FMS+ and FMS- compared to healthy subjects. Correlational analysis showed negative associations between TPT and D2/D3 receptor availability in the left caudate nucleus in FMS-, between TPT and D2/D3 receptor availability in the right caudate nucleus in FMS + and positive associations between TPT and D2/D3 receptor availability in the left putamen and right caudate nucleus in healthy controls. The response criterion was positively associated with D2/D3 receptor availability in the right nucleus accumbens in FMS - and negatively with D2/D3 receptor availability in the left caudate nucleus in healthy controls. Finally, no significant associations between D2/D3 receptor availability and discriminative capacity in any of the groups or regions were determined. These findings provide further support for a disruption of dopaminergic neurotransmission in FMS and implicate DA as important neurochemical moderator of differences in pain perception in FMS patients with and without co-morbid depression