Insensitivity of Lymphocytes of Patients with Neuropathic Pain Conditions to K+Channel Blockers

A reduced functioning of lymphocytes, where K+ channels play a fundamental role, has been reported in chronic pain conditions. We have therefore investigated the K+ channel activity in isolated lymphocytes of patients with complex regional pain syndrome (CRPS) or localised neuropathic pain (LNP) conditions compared with that of controls. K+ channel activity was determined using a Rb+ efflux assay in the lymphocytes from nine patients with CRPS and 13 patients with LNP and compared with results from 14 healthy controls and nine 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 from lymphocytes of the medical and healthy controls was significantly attenuated by margatoxin (10 nM) alone and in combination with charybdotoxin (100 nM). In contrast, the Rb+ efflux from lymphocytes of patients with CRPS or LNP was not modified by either treatment. The Rb+ efflux from lymphocytes of healthy controls was significantly lower than that of the other groups. The K+ channel blockers increased the level of significance relative to the CRPS and LNP groups, but decreased the level of significance relative to the medical controls. These findings are consistent with an abnormal functioning of K+ channels in lymphocytes from patients with CRPS or LNP, which may be relevant to the pain in these conditions.