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Table 1 Activation Profile of Opioid ligands in HEK-δ Cells

From: Activation profiles of opioid ligands in HEK cells expressing δ opioid receptors

LIGAND IC50 ± SEM (nM) Max Inhibition %
Butorphanol 61 ± 12 64 ± 4$
Cyclazocine 6 ± 3 53 ± 2**
Dezocine 477 ± 152 39 + 8
Etorphine 0.2 ± 0.1 67 ± 3$$
Fentanyl 2039 ± 554 71 ± 7$$ #
Hydromorphone 54 ± 31 65 ± 5$
Lofentanil 0.8 ± 0.4 62 ± 7$
Metazocine 159 ± 70 77 ± 4$$
Met-enkephalin 22 ± 17 49 ± 6##
Morphine 1101 ± 614 39 ± 4**
Nalbuphine 545 ± 378 55 ± 7*
Nalorphine Antagonist  
Naltrexone Antagonist  
SKF 10047 184 ± 121 68 ± 9$$
WIN 44,441 40 ± 25 54 ± 6*
Xorphanol 8 ± 2 76 ± 4$$ ##
  1. Inhibitory effect of opioid ligands on Forskolin-stimulated Adenylyl Cyclase activity was measured as described under Materials and Methods. Data for IC50's represent the mean ± SEM obtained from two or more experiments carried out in duplicate. Maximum inhibition is the mean ± SEM of maximum inhibition obtained from a best fit curve as described under "Materials and Methods" (** = P < 0.001, * = P < 0.05 compared to Metazocine), ($$ = P < 0.001, $ = P < 0.05 compared to morphine), (## = P < 0.001, # = P < 0.05 compared to met-enkephalin).