Journal: Clin Biochem. 2006 Jul 13; [Epub ahead of print] Authors and Affiliation: Bazzichi L, Giannaccini G, Betti L, Italiani P, Fabbrini L, Defeo F, Giacomelli C, Giuliano T, Rossi A, Uccelli A, Giusti L, Mascia G, Lucacchini A, Bombardieri S; Department of Internal Medicine, U. O of Rheumatology, University of Pisa, Italy. PMID: 16919618 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 [(3)H] 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 (B(max) was 5366+/-188 fmol/mg vs. controls, 4193+/-341 fmol/mg, mean+/-SEM) (**p<0.01) but not for affinity value (K(d) 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 B(max). 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.