Table 1. Properties of APs and Vm in bipolar-cell terminals
| Control | Picrotoxin | Nifedipine | |
|---|---|---|---|
| Data values were obtained from 13 control terminals, eight terminals in the presence of picrotoxin (50 μm) and six terminals in the presence of picrotoxin plus nifedipine (100 μm). Spontaneous APs were observed with no injected current, and evoked APs were observed with ≤+4 pA of injected current. AP amplitude refers to the size of the largest (low-frequency) APs observed in each terminal. AP duration was the width of large APs at 50% of the maximum amplitude. Max Vm was the most positive potential reached during a current ramp from 0 to +25 pA. Min Vm was the most negative potential reached during a current ramp from 0 to −10 pA. No significant differences were observed between terminals in control conditions and in the presence of picrotoxin. Max Vm was significantly more positive in the presence of nifedipine (P < 0.01, compared with in the presence of picrotoxin). | |||
| Spontaneous APs | 7/13 terminals | 5/8 terminals | 0/9 terminals |
| Evoked APs | 13/13 terminals | 8/8 terminals | 0/9 terminals |
| AP threshold (mV) | −63 ± 1 | −63 ± 1 | — |
| AP amplitude (mV) | 28 ± 3 | 29 ± 4 | — |
| AP duration (ms) | 16 ± 1 | 17 ± 2 | — |
| Max Vm (mV) | −33 ± 2 | −33 ± 2 | −6 ± 8* |
| Min Vm (mV) | −118 ± 7 | −135 ± 12 | −119 ± 15 |