Table 1.

Binding affinities and selectivities of I₂ receptor agonists at I₁, I₂ receptors and α₂ adrenoceptors

Drug	I1 (Ki or IC50, nM)	I2 (Ki, nM)	α2 (Ki, nM)	I2/I1	I2/α2	References
Tracizoline	19.1	1.9	14,118	10	7431	Polidori et al. (2000); Gentili et al. (2006)
2-BFI	6392*	1.3	3,736	4917	2874	Hudson et al. (1997)
BU224	1747	2.1	2,231	832	1062	Hudson et al. (1999)
Phenyzoline	3697	2.5	1,985	1479	794	Gentili et al. (2006; 2008)
S22687	370	45	11,000	8	244	Barrot et al. (2000)
Diphenyzoline	6340	158.5	7,079	40	45	Gentili et al. (2006; 2008)
CR4056	ND	596 (IC50)	N.D, but inactive at 10 µM		–	Ferrari et al. (2011)
Idazoxan	1259	10.6	55.4	119	5	Hudson et al. (1997); Eglen et al. (1998)
Efaroxan	52	>10,000	13	<0.005	<0.001	Eglen et al. (1998)

Selectivity (I₂/I₁ or I₂/α₂) was determined by comparing the K_i or IC₅₀ values of the compounds on both receptors.

^*Personal communication with Dr Alan L. Hudson, University of Alberta.

ND, not determined.