Table 1.

Human histamine H₁, H₃, and H₄ receptor affinities and fluorescence absorption and emission maximum wavelengths of novel non-imidazole ligands.

Compound	Structure	hH1R Ki [nM]a	hH3R Ki [nM]b	hH4R Ki [nM]c	λmax Abs. [nm]d	λmax Em. [nm]d	Stokes shift [nm]
Ciproxifan		>10,000e	46 ± 4f	612 ± 32g
1		3,473 ± 475	68 ± 12	100,535 ± 21,305
2		3,717 ± 873	89 ± 8	169,895 ± 118,942
3		791 ± 192	70 ± 21	12,370 ± 3,055	405	584	179
4		2,142 ± 886	149 ± 29	13,725 ± 1,110	397	583	186
5		881 ± 203	94 ± 26	5,634 ± 2,100	468	670	202
6		1,974 ± 89	101 ± 13	8,704 ± 204	467	674	207
7		1,968 ± 416	19 ± 5	37,260 ± 13,209
8		3,686 ± 950	17 ± 5	43,875 ± 9,581
9		1,768 ± 472	41 ± 4	12,598 ± 6,608	405	567	162
10		4,228 ± 1,121	97 ± 34	15,610 ± 5,841	405	583	178
11		1,374 ± 10	68 ± 3	6,400 ± 2,189	467	600	133
12		1,837 ± 837	87 ± 20	10,984 ± 3,403	467	607	140

^a[³H]Pyrilamine competition binding assay with membrane preparation of CHO-K1 cells expressing human histamine H₁ receptor. ^b[³H]N^α-Methylhistamine competition binding assay with membrane preparation of HEK-293 cells over-expressing human histamine H₃ receptor. ^c[³H]Histamine displacement assay with membrane preparation of Sf9 cells transiently expressing human histamine H₄ receptor and co-expressed with supporting G-Protein G_αi/o and G_β1γ2. K_i values are means ± SEM. ^dMeasured in buffer (12.5 mM MgCl₂, 100 mM NaCl, and 75 mM Tris/HCl, pH 7.4) at a concentration of 10 mM. ^eZhao et al. (2008). ^fLigneau et al. (2000). ^gGbahou et al. (2006).