Table 2.

GSK1004723 selectivity at human recombinant histamine receptors

	Human histamine receptor
	H1	H2	H3	H4
Test system	CHO-K1 membranes	HEK293 membranes	CHO-K1 membranes	HEK293 membranes
Assay format	Radioligand binding	cAMP production	Radioligand binding	Radioligand binding
Affinity estimate	pKi = 10.2 ± 0.24 (n = 4)	pIC50 ≤ 5.1 (n = 2)	pKi = 10.6 ± 0.03 (n = 4)	pIC50 ≤ 6.0 (n = 2)

K_i (shown as negative log, pK_i) calculated from IC₅₀ values determined under equilibrium conditions in competition binding experiments, using Cheng–Prusoff equation, as described under Data analysis and statistics. Data for H₁/H₃ are means ± SEM for four separate determinations. Competition binding experiments were carried out at 37°C for H₁/H₃ and ambient room temperature (20–22°C) for H₂/H₄.