▁vocals ▁ ▁The ▁Secret ▁Sister s ▁– ▁backing ▁vocals ▁ ▁k . d . ▁lang ▁– ▁backing ▁vocals ▁ ▁N ek o ▁Case ▁– ▁backing ▁vocals ▁ ▁Ch arts ▁ ▁References ▁ ▁External ▁links ▁▁ ▁M . ▁Ward ' s ▁official ▁home page ▁ ▁More ▁Rain ▁on ▁Mer ge ▁Records ▁ ▁Category : M . ▁Ward ▁albums ▁Category : 2 0 1 6 ▁albums <0x0A> </s> ▁Bu pr en orph ine - 3 - gl uc ur on ide ▁( B 3 G ) ▁is ▁a ▁major ▁active ▁met abol ite ▁of ▁the ▁op io id ▁mod ulator ▁bu pr en orph ine . ▁It ▁has ▁aff inity ▁for ▁the ▁ μ - op io id ▁re ceptor ▁( K i ▁= ▁ 4 . 9 ▁( ± ▁ 2 . 7 ) ▁p M ), ▁ δ - op io id ▁re ceptor ▁( K i ▁= ▁ 2 7 0 ▁n M ), ▁and ▁n oc ice pt in ▁re ceptor ▁( K i ▁= ▁ 3 6 ▁ μ M ), ▁but ▁not ▁for ▁the ▁ κ - op io id ▁re ceptor . ▁Whether ▁B 3 G ▁acts ▁as ▁an ▁ag on ist ▁or ▁ant agon ist ▁of ▁each ▁of ▁the ▁former ▁three ▁respective ▁sites ▁has ▁yet ▁to ▁be ▁determined . ▁In ▁r ats , ▁at ▁the ▁dos es ▁ass ay ed , ▁B 3 G ▁has ▁been ▁found ▁to ▁produce ▁a ▁small ▁degree ▁of ▁ant in oc ice ption , ▁and ▁similarly ▁to ▁bu pr en orph ine