Nicardipine inhibits N-type calcium channels in dbcAMP-differentiated neuroblastoma x glioma hybrid cells (NG 108-15 cells)

AIM: To investigate the possibility of dihydropyridine inhibition of N-type calcium channels. METHODS: Effects of nifedipine and nicardipine on the high Kf-induced intracellular Ca2+ concentration ([Ca2+](i)) increase were studied by measuring [Ca2+](i) using the fluorescent indicator Fura-2. RESULTS: Pretreatment of cells with nifedipine 50 mu mol L-l inhibited the high K+-induced [Ca2+](i) transient by about 60 % (n = 3); however, pretreatment of cells with nicardipine 10 mu mol.L-1 completely prevented the high Kt-evoked [Ca2+](i) increase in dibutyryl cyclic AMP (dbcAMP)-differentiated NG 108-15 cells (n =5). The high K+-induced [Ca2+](i) increase was mediated by L and N-type voltage-sensitive calcium channels (VSCC) in NC 108-15 cells. CONCLUSION: Nicardipine at micromolar range inhibited both L- and N-type VSCC in dbcAMP-differentiated NG 108-15 cells whereas nifedipine mainly inhibited L-type calcium channels.