Fig. 2. Effect of tetrodotoxin (TTX) and La³⁺(La) on N -methyl-d-aspartate (NMDA)–induced currents. (A ) Tetrodotoxin (0.5 μm) did not affect the amplitudes of NMDA-induced currents. However, bupivacaine (Bup; 2 mm) inhibited NMDA-induced currents in the presence of tetrodotoxin. (B ) The relative amplitudes were 101 ± 18% of the control level in the presence of tetrodotoxin and 59 ± 10% in the presence of tetrodotoxin + 2 mm bupivacaine. (C ) La³⁺(30 μm) could not affect NMDA-induced currents, but bupivacaine (2 mm) reduced the amplitudes of NMDA-induced currents in the presence of La³⁺. The relative amplitudes were 106 ± 26% of the control level in the presence of La³⁺and 61 ± 13% of control level in the presence of La³⁺+ 2 mm bupivacaine. *P < 0.01. NS = not significant.