Table 1.
Binding affinities for α1-AR antagonists at [3H]-silodosin and [3H]-prazosin binding sites in rat cerebral cortex
| Drug | [3H]-silodosin Segments | pKi low | Membranes | [3H]-prazosin Segments | pKi low | Membranes | pKi low |
|---|---|---|---|---|---|---|---|
| pKi high (%high) | pKi | pKi high (%high) | pKi high (%high) | ||||
| Prazosin | 9.9±0.2 (60±6%) | 7.8±0.3 | 10.0±0.2 | 9.9±0.2 | 10.2±0.1 | ||
| Silodosin | 9.8±0.3 | 9.9±0.1 | 9.9±0.3 (48±3%) | 7.9±0.3 | 10.0±0.2 (51±3%) | 8.1±0.2 | |
| Tamsulosin | 9.8±0.2 | 10.0±0.1 | 9.9±0.1 | 10.3±0.1 | |||
| BMY 7378 | 6.3±0.2 | 6.5±0.1 | 6.2±0.2 | 6.3±0.2 | |||
| RS-17053 | 8.7±0.2 (57±3%) | 6.8±0.2 | 9.1±0.2 | 8.9±0.3 (45±4%) | 7.8±0.2 | 9.0±0.2 (54±4%) | 7.1±0.2 |
| 5-Methylurapidil | 9.2±0.3 (55±4%) | 8.2±0.3 | 9.1±0.3 | 8.9±0.3 (45±4%) | 7.4±0.2 | 9.4±0.4 (52±5%) | 7.8±0.3 |
Abbreviations: %high, proportion of high affinity sites; ND, not determined; pKi high and pK low, negative logarithm of the equilibrium constants (pKi) at high and low affinity sites for tested drugs.
Competitive binding experiments with intact tissue segments and crude membrane preparations were carried out at 500 pM [3H]-silodosin or 300 pM [3H]-prazosin. Data represent mean±s.e.mean of 4–5 experiments.