Table 7.

Adenosine receptor affinities of functionalized xanthines as molecular probes

		Ki (nM)a
		A1	A2A	A2B	A3
Spin-labeled probes
155		5.47 (r)1	8,780 (r)1	>1,000 (h)1	1,700 (h)1
156		8.23 (r)1	3,800 (r)1	3,100 (h)1	ca. 10,000 (h)1
157		15.7 (r)1	1,270 (r)1	48 (h)1	350 (h)1
167	TEMPO-XAC	4.9 (r)2 0.30 (c)2	nd	nd	nd
Irreversible ligands
158	FSCPX3,4	10 (r)3	nd	nd	nd
160	ISC	42,600 (r)5 51,400 (gp)5 89,500 (rb)5 63,400 (c)5	146 (r)5 160 (gp)5 413 (rb)5 516 (c)5	nd	nd
164	m-DITC-XAC	2.39 (r)6 52 (r)7	nd	nd	nd
165	p-DITC-XAC	6.60 (r)6 27 (r)7	nd	nd	nd
Radioligands
159	[18F]CPFPX	1.26 (h)8 0.63 (r)8 1.37(p)8 0.18 (c)8	940 (h)8 812 (r)8	nd	nd
166		40 [IC50] (c) 9	nd	nd	nd
172	[125I]PAPA-XAC	0.1 (c)10	nd	nd	nd
Biotin conjugates
161		54 (r)11,12	nd	nd	nd
162		50 (r)11,12	nd	nd	nd
163		60 (r)12	nd	nd	nd
Various conjugates
168	D-Lys-XAC	1.74 [IC50] (r) 13	159 [IC50] (r)13	nd	nd
169		35 (r)12	nd	nd	nd
170		8.1 (r)2 0.8 (c)2	nd	nd	nd
171	DTPA-XAC	59.5 (r)2 3.25 (c)2	nd	nd	nd
Fluorescent ligands
173	FITC-XAC	125 (r)2 9.3 (c)2	nd	nd	nd
174	XAC-BY630	151 (h)14	nd	nd	nd
Bivalent ligand conjugates
17511,15		31 (r)	nd	nd	nd
176	A2A antagonist/D2 agonist for A2A/D2 receptor heteromers Ki D2 (s) = 1.0 nM)16	nd	55 (s)16	nd	nd

^ah = human; c = cow; d = dog; gp = guinea pig; p = pig; r = rat; rb = rabbit; s = sheep

¹Ilas et al., 2005

²Jacobson et al., 1987b

³Scammels et al., 1994

⁴Muijlwijk-Koezen et al., 2001

⁵Ji et al., 1993

⁶Jacobson et al., 1989a

⁷Stiles and Jacobson, 1988

⁸Holschbach et al., 2002

⁹Jacobson et al., 1992b

¹⁰Stiles and Jacobson, 1987

¹¹Jacobson, 2009

¹²Jacobson et al., 1987c

¹³Jacobson et al., 1986b

¹⁴Briddon et al. 2004

¹⁵Jacobson et al., unpublished

¹⁶Soriano et al., 2009