Table 3.

Affinities of unlabelled antagonists at Nluc-H₁R measured in whole cells and membranes.

Compound	25 nM 10				25 nM 23
	Whole cells		Membranes		Whole cells
	pKi	n	pKi	n	pKi	n
Promethazine	8.12 ± 0.02†	5	8.67 ± 0.07†	4	7.94 ± 0.12	4
Mepyramine	7.62 ± 0.05*	5	7.77 ± 0.14	4	7.28 ± 0.12*	5
Loratadine	6.48 ± 0.05†	5	6.21 ± 0.09†	4	6.36 ± 0.10	4
Triprolidine	7.55 ± 0.11	4	7.77 ± 0.09	4	7.34 ± 0.13	5
Doxepin	8.36 ± 0.10†	5	9.06 ± 0.15†	4	8.30 ± 0.13	5
Olopatadine	7.73 ± 0.10*†	5	8.40 ± 0.13†	4	8.05 ± 0.04*	4
Fexofenadine	6.78 ± 0.18	5	7.00 ± 0.11	4	6.70 ± 0.10	4
Levocetirizine	7.28 ± 0.06†	3	7.66 ± 0.08†	4	7.38 ± 0.10	5

pK_i values of eight H₁R antagonists in HEK293T cells or membranes expressing Nluc-H₁R were determined by competition binding with 25 nM 10 (whole cells and membranes) or 25 nM 23 (whole cells only). All values represent mean ± SEM from n separate experiments performed in triplicate. ^*p < 0.05 pK_i measured using 10 versus 23 (Student’s unpaired t test). ^†p < 0.05 pK_i measured using 10 in whole cells versus membranes (Student’s unpaired t test).