In isolated rat hippocampal neurons, we observed 4 voltage- and extracellular Ca2+-dependent conductances; i.e. the T-, N- and L-type Ca2+ currents and tetrodotoxin-sensitive transient Ca2+ current. Intracellular perfusion with F- suppressed irreversibly the L-type Ca2+ current and partially the N-type one. omega-Conotoxin inhibited selectively the L-type Ca2+ current. Amiloride reduced strongly the T-type Ca2+ current without affecting the L-type one. Gd3+, nicardipine, phenytoin and octanol had no specific inhibition on the T-, N- and L-type Ca2+ currents. Thereby, the pharmacological property of mammalian CNS neurons for Ca2+ channel blockers considerably differs from that in the peripheral and cultured cells.