Changes in Platelet Alpha-2-Adrenoceptors in Fibromyalgia: Effects of Treatment with Antidepressants

The aim of this study was to determine platelet α<sub>2</sub>-adrenergic receptor (α<sub>2</sub>-AR) binding sites in fibromyalgia both before and after treatment with sertraline or placebo. The maximum number of binding sites (B<sub>max</sub>) and their affinity (K<sub>d</sub>) for [<sup>3</sup>H]rauwolscine, a selective α<sub>2</sub>-AR antagonist, were measured in 13 normal volunteers and 22 fibromyalgia patients. Severity of illness was evaluated by means of the Hamilton Depression Rating Scale (HDRS) and dolorimetric assessments of tenderness at tender points. Fibromyalgia patients had repeated measurements of [<sup>3</sup>H]rauwolscine binding characteristics both before and after subchronic treatment with sertraline or placebo for 12 weeks. [<sup>3</sup>H]rauwolscine binding K<sub>d</sub> values were significantly higher in fibromyalgia patients than in normal volunteers. There were significant inverse correlations between [<sup>3</sup>H]rauwolscine binding K<sub>d</sub> values and duration of illness, age and lower energy. Significantly higher [<sup>3</sup>H]rauwolscine binding K<sub>d</sub> values were found in fibromyalgia patients in an early phase of illness (<3 years) than in fibromyalgia patients with a protracted illness (>3 years). Repeated administration of sertraline had no significant effects on [<sup>3</sup>H]rauwolscine binding B<sub>max</sub> or K<sub>d</sub> values. The results suggest that fibromyalgia and, in particular, fibromyalgia in an early phase of illness, is accompanied by lowered affinity of platelet α<sub>2</sub>-ARs.