Inhibition of [3H]MK-801 binding to rat hippocampal membranes (CA1/DG) by Zn2+ and by ifenprodil
| Extent of Inhibition | IC50 | nH | ||||
|---|---|---|---|---|---|---|
| Control | 10 μM Spermine | Control | 10 μM Spermine | Control | 10 μM Spermine | |
| fmol/mg tissue | μM | |||||
| Inhibition by Zn2+ | ||||||
| High-affinity component | 26.4 ± 2.4 | 40.6 ± 3.2 | 5.5 ± 1.6 | 24.4 ± 8.6 | 1.35 ± 0.22 | 1.29 ± 0.14 |
| (8) | (8)b | (8) | (8)b | (8) | (4) | |
| Low-affinity component | 14.4 ± 3.4 | 17.2 ± 4.2 | 1970 ± 910 | 1560 ± 1010 | N.D. | N.D. |
| (8) | (8)1-a | (6) | (6) | |||
| Inhibition by ifenprodil | ||||||
| High-affinity component | 7.6 ± 2.3 | 17.4 ± 4.1 | 0.18 ± 0.08 | 1.09 ± 0.52 | 0.95 ± 0.21 | 1.06 ± 0.34 |
| (11)d | (11)b d | (11) | (11)b | (8)c | (10) | |
| Low-affinity component | 29.5 ± 5.1 | 40.2 ± 6.4 | 362 ± 81 | 330 ± 93 | N.D. | N.D. |
| (11)d | (11)b d | (9) | (9) | |||
Values are mean ± S.D., with the number of experiments in parentheses. The mean EC50 value for spermine stimulation of [3H]MK-801 binding has been 3.41 ± 0.90 μM (4) for experiments with Zn2+ and 2.76 ± 0.90 μM (7) for experiments with ifenprodil.
↵1-a P < .01, b P< .001, significantly different from control (paired Student’st test). c P < .01,d P < .001, significantly different from corresponding value obtained with Zn2+ (ANOVA).
N.D., not determined (for computerized curve fitting, the Hill coefficient nH was set equal to 1.0).