Table 3. Some σR ligands in order of their potency.

σR ligands in rough order of potency
σ1R ligands	σ2R ligands
(+)-pentazocine [PTZ]	1,3 di-o-tolyl-guanidine [DTG]
Haloperidol	Haloperidol
1,3 di-o-tolyl-guanidine [DTG]	(+)-3-PPP [preclamol)
(+)-3-PPP	(−)-pentazocine
Dextromethorphan [DEX]	Phencyclidine
(+)-SKF 10,047	(+)-pentazocine
(+)-cyclazocine	(−)-SKF 10,047
(−)-pentazocine	BD1047
Phencyclidine	BD1063
(−)-SKF 10,047