TABLE 1

o-DTG binds to both σ receptor subtypes with greater affinity than p-BrDPhG

Mean K_i values ± S.E.M. determined from binding assays using membrane protein extracts from rat livers. σ-1 receptors were labeled with 5 nM [³H](+)-pentazocine, and σ-2 receptors were labeled with 3 nM [³H]o-DTG in the presence of 300 nM (+)-pentazocine to block σ-1 receptors. Nonspecific binding was determined in the presence of 50 µM haloperidol.

Variable	Receptor^*	Mean K_i	S.E.M.
		nM
o-DTG	σ-1	91.02	9.7
	σ-2	60	8.76
p-BrDPhG	σ-1*	296	46.01
	σ-2*^#	800.33	56.96

↵* Significant difference between p-BrDPhG and o-DTG binding at σ-1 (P < 0.001) and σ-2 (P < 0.001) receptors.
↵# Significant difference between p-BrDPhG affinity for σ-1 vs. σ-2 sites.