Efficacies (Emax values) and potencies (pEC50 or pKb values) of antiparkinson agents at recombinant hD2S, hD2L, hD3, and hD4 receptors
| Ligand | hD2S | hD2L | hD3 | hD4 | ||||
|---|---|---|---|---|---|---|---|---|
| Emax | pEC50 orpK b | Emax | pEC50orpK b | Emax | pEC50 | Emax | pEC50or pK b | |
| Apomorphine | 79 ± 6 | 7.71 | 53 ± 3 | 7.66 | 82 ± 5.7 | 7.93 | 45 ± 3 | 8.23 |
| Bromocriptine | 41 ± 1 | 8.35 | 28 ± 2 | 8.41 | 68 ± 7.2 | 8.38 | 01-a | < 51-a |
| Cabergoline | 102 ± 1 | 9.27 | 75 ± 5 | 9.39 | 86 ± 6.7 | 9.11 | 49 ± 1 | 7.09 |
| Lisuride | 55 ± 1 | 9.54 | 21 ± 3 | 9.14 | 49 ± 9.3 | 9.24 | 32 ± 31-a | 8.231-a |
| Pergolide | 112 ± 3 | 8.06 | 52 ± 3 | 8.07 | 71 ± 9.4 | 9.29 | 56 ± 41-a | 7.531-a |
| Piribedil | 42 ± 8 | 6.71 | 21 ± 2 | 6.56 | 34 ± 2.3 | 6.91 | 7 ± 3 | 5.37 |
| Pramipexole | 130 ± 2 | 6.37 | 70 ± 8 | 6.47 | 70 ± 2.2 | 8.65 | 42 ± 1 | 6.89 |
| Quinelorane | 119 ± 6 | 6.85 | 105 ± 8 | 6.71 | 79 ± 1.5 | 9.17 | 72 ± 21-a | 7.831-a |
| Quinpirole | 132 ± 81-b | 6.091-b | 74 ± 2 | 6.23 | 67 ± 2.11-b | 8.171-b | 69 ± 41-c | 7.21 |
| Ropinirole | 108 ± 6 | 6.18 | 52 ± 3 | 6.38 | 59 ± 4 | 7.56 | 74 ± 21-a | 5.541-a |
| Roxindole | 11 ± 11-c | 9.05 | 0 | 9.54 | 30 ± 5.41-c | 9.231-c | 35 ± 31-c | 7.691-c |
| Talipexole | 89 ± 11 | 6.43 | 71 ± 5 | 6.48 | 88 ± 9.0 | 7.69 | 49 ± 4 | 6.21 |
| Terguride | 39 ± 4 | 9.34 | 0 | 9.62 | 36 ± 3.2 | 9.18 | 0 | 8.31 |
| TL 99 | 92 ± 3 | 7.75 | 46 ± 4 | 7.86 | 94 ± 8.5 | 8.91 | 71 ± 2 | 7.16 |
Efficacy (Emax) and potency (pEC50 orpK b) values at hD2S, hD2L, hD3, and hD4 receptors were determined by [35S]GTPγS binding. pEC50 values for stimulation are indicated in normal case and pK b values for inhibition are indicated in bold. Emax values are percentages of the stimulation observed with a maximally efficacious (Emax = 100%) concentration of dopamine (see Materials and Methods) and are expressed as means ± S.E.M. values of at least three independent determinations performed in triplicate. pEC50 values are means of at least three independent determinations: S.E.M.s values (not shown) were less than 0.2 log units. Dopamine exhibited pEC50 values of 6.46, 6.49, 7.95, and 7.00 at hD2S, hD2L, hD3, and hD4 receptors, respectively. For piribedil, thepKb at hD4 receptors is indicated in the table. It exhibited an agonist pEC50 value of 6.4 at these sites. For roxindole, the pK b at hD2S receptors is given in the table. It exhibited an agonist pEC50 value of 8.11 at these sites.