Function of Potassium Channels in Blood Mononuclear Cells of Patients with Fibromyalgia

K+ channel function, which has been associated with modulation of chronic pain conditions, is abnormal in peripheral blood mononuclear cells (PBMC) of patients with neuropathic pain. Therefore, K+ channel activity and sensitivity of their function to selective K+ channel blockers was investigated in isolated PBMC of patients with fibromyalgia compared with that of controls. K+ channel activity was determined, using a Rb+ efflux assay, in PBMC from 13 patients with fibromyalgia and compared with results from 14 healthy controls and nine cardiovascular medical controls. K+ channels were stimulated by KCl-induced membrane depolarization and characterized using the K+ channel blockers, margatoxin and charybdotoxin. Increasing the extracellular KCl concentration augmented the Rb+ efflux in all groups. The stimulated Rb+ efflux did not differ among patients with fibromyalgia (34.7 ± 3.5%) and healthy controls (33.5 ± 3.0%), but responses from samples of medical controls (45.8 ± 3.8%) were greater than those of healthy controls (P < 0.05), but not fibromyalgia patients. Exposure of the PBMC to the K+ channel blockers, margatoxin and charybdotoxin, did not change the between-group comparisons of the data. These data indicate that the K+ channel activity in PBMC from patients with fibromyalgia did not differ from that observed in cells from healthy controls, in contrast to that previously reported for patients with neuropathic pain conditions.