Pharmacology of HM1(S388Y) and HM1(T389P) receptors
| Ligand | HM1(S388Y) 2,600 ± 160 fmol/mg | HM1(S388Y, T389P)2-a 2,600 ± 690 fmol/mg | HM1(T389P) 1,200 ± 210 fmol/mg | HM1(WT)2-a 260 ± 29 fmol/mg | ||||
|---|---|---|---|---|---|---|---|---|
| Smax | EC50 | Smax | EC50 | Smax | EC50 | Smax | EC50 | |
| % | nM | % | nM | % | μM | % | μM | |
| ACh | 410 ± 23 | 8.3 ± 3.6 | 550 ± 95 | 4.8 ± 1.6 | 320 ± 77 | 0.87 ± 0.71 | 370 ± 66 | 1.5 ± 0.19 |
| CCh | 430 ± 27 | 130 ± 53 | 520 ± 77 | 59 ± 3.5 | 300 ± 89 | 3.7 ± 0.69 | 350 ± 55 | 13 ± 1.1 |
| Choline | 390 ± 31 | 160,000 ± 85,000 | 420 ± 68 | 200,000 ± 20,000 | 110 ± 5.8 | 2,700 ± 1,500 | 2.6 ± 7.7 | N.A. |
| Oxo-M | 420 ± 22 | 26 ± 9.9 | 510 ± 45 | 12 ± 5.4 | 330 ± 89 | 3.9 ± 2.0 | 310 ± 29 | 0.80 ± 0.15 |
| Oxo | 440 ± 46 | 13 ± 5.3 | 500 ± 100 | 18 ± 2.8 | 180 ± 46 | 0.91 ± 0.33 | 110 ± 28 | 0.22 ± 0.030 |
| Arecoline | 330 ± 4.8 | 120 ± 65 | 510 ± 100 | 60 ± 14 | 250 ± 46 | 13 ± 5.4 | 150 ± 26 | 3.6 ± 0.70 |
Receptor expression levels were determined from [3H](R)-QNB saturation binding assays on membrane homogenates prepared from stably transfected A9 L cells. PI hydrolysis was carried out in KH buffer to exclude potential effects of choline in media and unknown muscarinic agonists in serum. Data represent the mean ± S.E. from a minimum of three assays, each performed in duplicate.
↵2-a Data are from Huang et al. (1998) and included for comparison.
Smax (%) represents the maximal stimulation expressed as the percentage above basal levels. N.A., not applicable.