TABLE 2

Effects of different opioid antagonists on basal [³⁵S]GTPγS binding in MOR cell membranes with or without agonists pretreatment

Maximal effects (E_max) are expressed as percentage of change from basal. Positive values indicate agonistic effects, whereas negative values indicate inverse agonist effects. Data are means ± S.D., n = 4 to 8.

Compound	No Pretreatment			Pretreatment
	No Pretreatment					DAMGO		Morphine
		EC₅₀	E_max	EC₅₀	E_max	EC₅₀	E_max
	nM	% change	nM	% change	nM	% change
DAMGO	74 ± 13	92 ± 5	164 ± 59^*	69 ± 7^*	N.D.	N.D.
BNTX	402 ± 250	-7 ± 2^**	31 ± 16^*	-13 ± 1^,^*	57 ± 15^*	-14 ± 1^,^*
Naloxone	2 ± 1	14 ± 1^**	7 ± 2	-9 ± 1^,^*	N.D.	-9 ± 3^,^*
Naltrexone	N.D.	29 ± 6^**	N.D.	-8 ± 2^,^*	N.D.	-8 ± 1^,^*
6β -Naltrexol	3 ± 2	12 ± 1^**	N.D.	1 ± 2^*	N.D.	2 ± 5^*
6β -Naltrexamide	3 ± 2	22 ± 1^**	29 ± 15^*	17 ± 1	N.D.	12 ± 6^*

N.D., not determined.
↵* P < 0.01, compared with no pretreatment.
↵** P < 0.01, compared with zero; ANOVA with Dunnett's post test.