Table 4.

Thermodynamic parameters of binding to histamine H₃-receptors in guinea-pig cerebral cortex membranes in buffer A

Ligand	Intrinsic activity (α)	ΔGo′ calculated (kJ mol−1)a	ΔGo′ (kJ mol−1)	ΔHo′ (kJ mol−1)	−TΔSo′ (kJ mol−1)	ΔSo′ (J mol−1 K−1)	n
Histamine H3-receptor agonists
immepip	1.00b	−53.8±0.3	−53.4±0.2	9.1±10.0	−62.5±9.9	211.7±33.3	5
imetit	0.90b,c	−52.6±0.7	−51.9±0.8	6.4±6.2	−58.3±6.9	197.8±23.3	4
R-α-MH	1.00c	−51.6±1.0	−51.2±1.1	19.1±3.9	−70.3±4.0	218.3±14.2	5
proxyfan	0.35c	−48.6±1.0	−47.4±0.7	44.5±9.2	−91.8±9.8	311.3±33.1	3
chloroproxyfan	0.45c	−46.9±2.9	−50.5±0.9	26.6±4.9	−77.1±5.8	261.4±19.7	5
bromoproxyfan	0.69c	−51.6±0.9	−52.2±0.2	14.2±13.4	−66.3±13.3	224.9±45.0	3
iodoproxyfan	0.90c	−55.3±0.3	−54.7±0.3	37.3±7.3	−92.0±7.3	311.0±24.4	4
Histamine H3-receptor antagonists
JB96132	0c	−51.8±0.7	−51.0±0.5	−34.1±6.5	−16.9±6.8	57.3±23.2	3
thioperamide	0c	−47.8±0.3	−48.0±0.3	−30.5±6.1	−17.5±6.1	59.3±20.6	6
[3H]clobenpropit	0c	−58.5±0.4	−58.0±0.3	−22.9±1.2	−35.1±1.3	119.5±4.4	3

Data are the mean±s.e.m.

^aΔG^o′ at 21°C, calculated using equation 2.

^ba values from Alves-Rodrigues et al., 2001

^cIntrinsic activity in guinea-pig ileum bioassay, see Harper et al. (2007).