Effects of NMDAR antagonists on B-cell membrane potential and K+channel activity. B cells were activated with α-IgM or LPS (10 μg/ml each) for 24–48 h. A) NMDAR antagonists lead to a depolarization of the membrane potential. Activated B cells were analyzed for changes in the membrane potential upon addition of ifenprodil or memantine in concentrations as indicated. KCl treatment served as a control for cell integrity. B-D) Ifenprodil and memantine inhibit K+ channel activity. Dose- inhibition curves of B) Kv1.3 and C) KCa3.1 channels in the presence of ifenprodil or memantine were plotted from the recorded maximal transient currents. Insets show one particular trace of control and inhibiting current along with the protocol used for measuring B) Kv1.3 and C) KCa3.1 channels. D) Data in the graphs represent the relative inhibition of Kv1.3- and KCa3.1-mediated currents in the presence of the competitive NMDAR antagonist D-APV. All data were calculated from 5–6 cells of four experiments and are represented as mean ± SD.