Affinity profiles of (±)-PG-9, R-(+)-hyoscyamine and AFDX-116 at muscarinic M1-receptors in rabbit vas deferens, M2-receptors in guinea-pig left atrium, M3-receptors in guinea-pig ileum and M4 putative-receptors in guinea-pig uterus2-a
| Drug | pA2 values | Selectivity ratios | |||||
|---|---|---|---|---|---|---|---|
| M1 rabbit vas deferens | M2 guinea pig left atrium | M3 guinea pig ileum | M4-putative guinea pig uterus | M4/M1 | M2/M1 | M4/M2 | |
| (±)-PG-9 | 6.71 ± 0.052-b | 6.85 ± 0.102-b | 6.84 ± 0.082-b | 7.72 ± 0.052-b | 10.2 | 1.4 | 7.4 |
| R-(+)-Hyoscyamine | 7.05 ± 0.052-c | 7.25 ± 0.042-c | 6.88 ± 0.052-c | 9.56 ± 0.012-c | 323 | 1.6 | 204 |
| AFDX-116 | 6.84 ± 0.142-d | 7.12 ± 0.112-d | 6.34 ± 0.132-e | 6.70 ± 0.06 | 0.7 | 1.9 | 0.4 |
↵2-a The ratios of affinity constants are given as a measure of receptor selectivity.
↵2-b pKB values are obtained with 1 μM (±)-PG-9 with the exception of the guinea pig uterus (0.1 μM). Each value is the mean of at least five experiments. pA2 values are the mean ± S.E.M. of 12 to 16 preparations. Selectivity ratios were calculated as antilogs of the difference between pKB or pA2values. Agonists used: McN-A-343 (rabbit vas deferens), carbachol (guinea pig left atrium and uterus) and ACh (guinea pig ileum) (see “Methods”).
↵2-c Ghelardini et al. (1993).
↵2-d Eltze (1988).
↵2-e Eltze and Figala (1988).