TABLE 3

Ligand binding properties of wild-type, T88^3.36A mutant, and S277^7.42A mutant adenosine A_2A receptors characterized in [³H]ZM241385 binding assays in competition with CGS21680 and LUF5834

The table shows the mean ± S.E.M. calculated from three independent experiments, each performed in duplicate. No significant differences were observed between the pK_i values of LUF5834 on the different constructs according to an unpaired t test. Change is expressed as the fold increase in the K_i value for the mutant over that for WT.

Construct	CGS21680			LUF5834
Construct	pK_{i High} (K_{i High})	pK_{i Low} (K_{i Low})	Change	pK_i (K_i)	Change
	nM		fold	nM	fold
Wild-type	6.8 ± 0.1 (159)	5.4 ± 0.1 (3680)	1.0	7.1 ± 0.2 (79.6)	1.0
T88^3.36A	N.D.	N.D.	>1000	6.9 ± 0.1 (127)	1.6
S277^7.42A	N.D.	N.D.	>1000	7.8 ± 0.0 (17.7)	0.2

N.D., not determined; the potency was too low to determine an accurate EC₅₀ value.