Table 3. Properties of Agonist-Stimulated [³⁵S]GTPγS Binding in Membranes from Whole Brain of Wild-Type and Gα_o Transgenic Mice.

Tissue	Genotype	Basal [35S]GTPγS binding	Agonist-stimulated [35S]GTPγS binding				DAMGO-stimulated [35S]GTPγS saturation binding
		(fmol/mg protein)	DAMGO		Morphine
			Emax (fmol/mg protein)	EC50 (nM)	Emax (fmol/mg protein)	EC50 (nM	Bmax (pmol/mg protein)	K (nM)
Whole brain	Wild type	62.2±2.5	71.3±3.2	287±91	39.4±4.5	165±14	8.31±1.01	14.2±4.0
	Gαo +/−	49.1±5.8	59.4±4.0	382±23	25.6±3.9	350±76	4.26±1.31	16.5±6.7
	Gαo −/−	22.2±0.3**, +	13.1±2.3***, +++	NC	5.2±1.0**	NC	1.18±0.53*	7.1±4.4
Spinal cord	Wild type	59.0±10.9	46.4±5.4	ND	36.3±4.0	ND	ND	ND
	Gαo +/−	49.0±11.1	35.0±6.7#	ND	19.5±3.1##	ND	ND	ND

Abbreviations: NC, not calculated; ND, not determined.

Agonist-stimulated [³⁵S]GTPγS binding is defined as the increase in [³⁵S]GTPγS incorporation in the presence of agonist, over that of basal (measured in the absence of agonist). Data represent the mean±SEM (n=2–3 performed in duplicate). Symbols indicate a statistical difference vs wild type whole brain (^*p<0.05, ^**p<0.01, ^***p<0.001) or Gα_o +/– whole brain (⁺p<0.05, ⁺⁺⁺p<0.001) by Bonferroni's post-test or vs wild-type spinal cord by Student's paired t-test (^#p<0.05, ^##p<0.01).