Table 1

Binding parameters for inhibition of [³H]RX821002 by dopamine and norepinephrine at α₂ adrenoceptor subtypes

Receptor System		Dopamine	Norepinephrine
NRK-α_2A	K _{i high affinity}	3.3 ± 0.93	1.4 ± 0.48
	K _{i low affinity}	63 ± 14	25 ± 2.6
	% High affinity	27 ± 6.1	24 ± 5.3
NRK-α_2C	K _{i high affinity}	0.18 ± 0.11	0.16 ± 0.073
	K _{i low affinity}	9.5 ± 0.27	6.1 ± 0.85
	% High affinity	19 ± 2.7^1-a	38 ± 5.7

↵1-a p < .05 compared with norepinephrine (Student’s t test). Each value is the mean ± S.E.M. of four separate determinations.
K_i values given in μM concentrations.