Figure 2.

(A) Radioligand displacement of helianorphins 1–4 on HEK293 membrane preparations stably expressing the mouse KOR (n = 3). Dynorphin A (dyn A) 1–13 was used as a positive control (n = 3). (B) Concentration-dependent cAMP inhibition following receptor activation by helianorphin-1 and -2 (n = 3) and helianorphin-3 and -4 (n = 4) in HEK293 cells stably expressing the mouse KOR. Dynorphin A (dyn A) 1–13 was used as a positive control (n = 3). (C) Two-point radioligand displacement assay of helianorphins 5–13 (n = 3) and (D) helianorphins 14–19 (n = 5) at the mouse KOR. Radioligand [³H]-diprenorphine (DPN; 1 nM) with or without 10 μM (dark gray bars) or 100 nM (white bars) of helianorphins was used. Dynorphin A (dyn A) 1–13 was used as a positive control (n = 3). Specific binding was obtained by subtraction of nonspecific binding from total binding. Data are presented as mean ± SD and are normalized to the percentage of maximum binding.