Depolarization is almost eliminated in the presence of: kynurenate (2 mm; n = 10; A), AP-V–DNQX (100 μm–10 μm; n = 6; B), TTX (0.1 μm; n = 7; C), Cd2+ (200 μm; n = 6; D). Picrotoxin (50 μm; n = 4; E) does not affect membrane depolarization. Because both type 1 and 2 responding cells had similar suppression of depolarization, all data are presented together. Responses under pharmacological treatment that were statistically different from their respective control and washout values are indicated (* initial depolarization, ** mean sustained depolarization, P < 0.05).