Table 3.

Affinities of 1,4-Dihydropyridine Derivatives in Radioligand Binding Assays at A₁, A_2A, and A₃ Receptors

compd	R3	chirality at 4-position	R5	Ki (μM) or % inhibitiond
				rA1a	rA2Ab	hA3c	rA1/hA3
2	OCH2CH3	racemic	OCH2Ph	40.1 ± 7.5e	d (10−4)	0.0222 ± 0.0038 (0.0314 ± 0.0028)e	1800
9		S	OCH2CH3	32 ± 4% (10−4)	d (10−4)	1.31 ± 0.57	>70
10		R	OCH2CH3	16.4 ± 3.1	d (10−4)	0.426 ± 0.133	38
11		S	OCH2CH3	14.8 ± 1.0	39 ± 8% (10−4)	0.52	28
12		R	OCH2CH3	6.83 ± 0.20	d (10−4)	0.65	11
21	OCH2CH3	S	OCH2Ph	32 ± 12% (10−4)	14 ± 6% (10−4)	0.0213 ± 0.0065	>400
23	OCH2CH3	R	OCH2Ph	25 ± 11% (10−4)	11 ± 4% (10−4)	0.750 ± 0.151	>15
28 e	OCH2CH3	racemic	OCH2CH3	11.0 ± 0.1	26 ± 12% (10−4)	0.0766 ± 0.0151	140

^aDisplacement of specific [³H]R-PIA binding in rat brain membranes, expressed as K_i (SEM in μM (n = 3–5), or as a percentage of specific binding displaced at the indicated concentration (M).

^bDisplacement of specific [³H]CGS 21680 binding in rat striatal membranes, expressed as K_i ± SEM in μM (n = 3–6), or as a percentage of specific binding displaced at the indicated concentration (M).

^cDisplacement of specific [¹²⁵I]AB-MECA binding at human A₃ receptors expressed in HEK cells, in membranes, expressed as K_i ± SEM in μM (n = 3–4).

^dDisplacement of 10% of specific binding at the indicated concentration (M).

^eValues taken from van Rhee et al.¹ or from Jiang et al.³