TABLE 1.
Effects of 4-AP on the voltage-dependent activation and inactivation of L-type, N-type, and P/Q-type Ca2+ channels in HEK293 cells cotransfected with α2δ1 and Cavβ2 or Cavβ3
n = 8–10 cells in each group; data are expressed as means ± S.E.M.
| Specific Subunit Combination | V0.5 | Slope Factor | |
|---|---|---|---|
| mV | mV | ||
| Voltage-Dependent Activation | |||
| L-type | Cav1.2+α2δ1+Cavβ2 (control) | −6.2 ± 0.1 | 7.0 ± 0.1 |
| Cav1.2+α2δ1+Cavβ2 (1 mM 4-AP) | −8.0 ± 0.1 | 5.6 ± 0.1 | |
| Cav1.2+α2δ1+Cavβ3 (control) | −6.2 ± 0.1 | 6.1 ± 0.1 | |
| Cav1.2+α2δ1+Cavβ3 (1 mM 4-AP) | −18.1 ± 0.1* | 5.7 ± 0.1 | |
| N-type | Cav2.2+α2δ1+Cavβ2 (control) | −6.4 ± 0.1 | 4.8 ± 0.1 |
| Cav2.2+α2δ1+Cavβ2 (3 mM 4-AP) | −9.2 ± 0.1 | 4.6 ± 0.1 | |
| Cav2.2+α2δ1+Cavβ3 (control) | −6.8 ± 0.1 | 4.8 ± 0.1 | |
| Cav2.2+α2δ1+Cavβ3 (3 mM 4-AP) | −18.9 ± 0.1* | 5.0 ± 0.1 | |
| P/Q-type | Cav2.1+α2δ1+Cavβ2 (control) | −8.1 ± 0.1 | 5.4 ± 0.1 |
| Cav2.1+α2δ1+Cavβ2 (3 mM 4-AP) | −8.1 ± 0.1 | 5.3 ± 0.1 | |
| Cav2.1+α2δ1+Cavβ3 (control) | −6.7 ± 0.1 | 5.6 ± 0.1 | |
| Cav2.1+α2δ1+Cavβ3 (3 mM 4-AP) | −8.1 ± 0.1 | 5.3 ± 0.1 | |
| Voltage-Dependent Inactivation | |||
| L-type | Cav1.2+α2δ1+Cavβ2 (control) | −19.6 ± 0.3 | −8.4 ± 0.2 |
| Cav1.2+α2δ1+Cavβ2 (1 mM 4-AP) | −18.7 ± 0.3 | −8.4 ± 0.3 | |
| Cav1.2+α2δ1+Cavβ3 (control) | −28.3 ± 0.3 | −8.1 ± 0.3 | |
| Cav1.2+α2δ1+Cavβ3 (1 mM 4-AP) | −28.2 ± 0.3 | −8.2 ± 0.3 | |
| N-type | Cav2.2+α2δ1+Cavβ2 (control) | −24.8 ± 0.3 | −7.8 ± 0.2 |
| Cav2.2+α2δ1+Cavβ2 (3 mM 4-AP) | −24.2 ± 0.3 | −7.7 ± 0.3 | |
| Cav2.2+α2δ1+Cavβ3 (control) | −51.2 ± 0.5 | −7.9 ± 0.3 | |
| Cav2.2+α2δ1+Cavβ3 (3 mM 4-AP) | −48.8 ± 0.4 | −7.6 ± 0.3 | |
| P/Q-type | Cav2.1+α2δ1+Cavβ2 (control) | −20.2 ± 0.3 | −9.1 ± 0.2 |
| Cav2.1+α2δ1+Cavβ2 (3 mM 4-AP) | −20.0 ± 0.3 | −9.0 ± 0.3 | |
| Cav2.1+α2δ1+Cavβ3 (control) | −23.4 ± 0.4 | −9.3 ± 0.3 | |
| Cav2.1+α2δ1+Cavβ3 (3 mM 4-AP) | −22.2 ± 0.3 | −9.0 ± 0.4 |
*
P < 0.05, compared with the respective control before 4-AP (paired Student’s t test).