Alteration of serotonin transporter density and activity in fibromyalgia

The aim of the study was to evaluate the kinetic parameters of a specific serotonin transporter (SERT) and serotonin uptake in a mentally healthy subset of patients with fibromyalgia. Platelets were obtained from 40 patients and 38 healthy controls. SERT expression and functionality were evaluated through the measurement of [H-3] paroxetine binding and the [H-3] serotonin uptake itself. The values of maximal membrane binding capacity (B-max) were statistically lower in the patients than in the healthy volunteers, whereas the dissociation constant (K-d) did not show any statistically significant variations. Moreover, a decrease in the maximal uptake rate of SERT (V-max) was demonstrated in the platelets of patients, whereas the Michaelis constant (K-m) did not show any statistically significant variations. Symptom severity score ( tiredness, tender points index and Fibromyalgia Impact Questionnaire) were negatively correlated with B-max and with V-max, and positively correlated with K-m. A change in SERT seems to occur in fibromyalgic patients, and it seems to be related to the severity of fibromyalgic symptoms.