TABLE 1.

Adenosine Analogs: Affinity for Rat Brain A₃-Adenosine Receptors and EC₅₀ Values for Stimulation of [³H]IP₁ Formation and Elevation of Intracellular Calcium in a Rat RBL-2H3 Mast Cell Line

		RBL-2H3 cells
	Rat brain	Stimulation	Elevation of [Ca²⁺]_i
Analog^a	A₃-receptors K_i (nM)^b	[³H]IP₁ EC₅₀^c (µM)	EC₅₀^d (µM)	Relative efficacy^e
2-CI-IBMECA	0.33	4.1 ± 1	0.07 ± 0.04	60
IBMECA	1.1	8.5 ± 1.7	0.11 ± 0.00	55
CHNECA	16	12.2 ± 2.1	0.4	54
NECA	113	2.1 ± 0.3	1.37 ± 0.18	100
APNEA	116	7.5 ± 1.5	0.9	38
BZADO	120	12.7 ± 2.6	2.7	60
R-PIA	158	5.5 ± 0.9	2.4	38
CHA	167	11.6 ± 1.1	0.88 ± 0.00	30
CGS 21680	584	5.8 ± 0.6	0.79 ± 0.02	28
ADO	~1,000	11.8 ± 1.1	1.45 ± 0.25	72
2-CIADO	1890	8.1 ± 1.5	1.7	25
8-BrADO	>100,000	13.9 ± 1.0	Inactive

Abbreviations in legend to Fig. 1.

Data from Gallo-Rodriguez et al. (1994), Van Galen et al. (1994), and Jacobson et al. (1995).

EC₅₀ values determined from data of Fig. 1A.

EC₅₀ values determined from data such as that presented in Fig. 4. Values are means ± s.e.m. (n = 3) or are from single determinations.

Efficacies relative to NECA set equal to 100 estimated from data such as those presented in Fig. 4.