Peripheral benzodiazepine receptors on platelets of fibromyalgic patients

Objective: The aim of the present study was to analyze if alterations of peripheral-type benzodiazepine receptor (PBR) characteristics occurred in platelet membranes of patients affected by primary fibromyalgia (FM). Design and methods: Platelets were obtained from 30 patients with FM. Evaluation of kinetic parameters of PBR was performed using [3H] PK11195 as specific radioligand compared with 16 healthy volunteers. Results: The results showed a significant increase of PBR binding sites value in platelet membranes from FM patients (Bmax was 5366 ± 188 fmol/mg vs. controls, 4193 ± 341 fmol/mg, mean ± SEM) (**p < 0.01) but not for affinity value (Kd was 4.90 ± 0.39 nM vs. controls, 4.74 ± 0.39 nM, mean ± SEM) (p > 0.05). Symptom severity scores (pain and tiredness) were positively correlated with Bmax. Conclusions: Our results showed an up-regulation of PBR in platelets of FM patients, and this seems to be related to the severity of fibromyalgic symptoms.