Hippocampal CA1 pyramidal cells of rats have four voltage-dependent calcium conductances

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. ω-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.