Table 1

Potencies and efficacies of TCAs in stimulating [³⁵S]GTPγS binding in CHO/DOR cells

	K_i^a	[³⁵S]GTPγS Assay			Cyclic AMP Assay
	K_i^a	EC₅₀	E_max	%E_max^b	EC₅₀	E_max	%E_max^b
	μM	μM			μM
Amoxapine	2.5 ± 0.5	0.98 ± 0.08	87 ± 2	96 ± 3	3.4 ± 0.5	42 ± 3	72 ± 2
Amitriptyline	28.1 ± 1.2	23.5 ± 1.2	72 ± 3	79 ± 5	16.2 ± 0.8	43 ± 4	74 ± 4
Nortriptyline	30.0 ± 1.0	22.6 ± 2.0	77 ± 2	85 ± 3
Desipramine	40.1 ± 2.5	35.5 ± 3.5	53 ± 2	59 ± 3
Imipramine	49.8 ± 3.5	46.8 ± 4.0	69 ± 3	76 ± 4

↵a Determined by radioligand binding displacement.
↵b Percentage of maximal stimulation with respect to that elicited by DPDPE. Values are the mean ± S.E.M. of at least three experiments.