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. Author manuscript; available in PMC: 2009 Aug 1.
Published in final edited form as: Peptides. 2008 Apr 10;29(8):1413–1423. doi: 10.1016/j.peptides.2008.03.022

Table 2.

Binding Affinities and Functional Activities of the CCK/Opioid Peptides at the δ and µ Opioid Receptors

Binding Affinity [35S]GTP-γ-S binding
Peptidea hDORb, [3H]DPDPEc rMORb, [3H]DAMGOd hDORb rMORb
Log IC50e Ki/nMf Log IC50e Ki/nMf Log EC50g EC50/nM ECmaxh Log EC50g EC50/nM Emaxh
1 0.2 2.2 780 190 42 69
2 3.8 9.2 200 110 25 110
3 0.3 1300 14 150 110 42
4 2.6 1.4 1.8 44 1.7 45
5 57 43. n/d n/d 42 69
6 510 1500 2000 43 5400 58
RSA504 23. 27 5.5 81 0.47 110
DPDPE n.d. - n.d. - −8.8±0.25 1.6 69±4.2 - -
DAMGO CCK-8 n.d. - n.d. - n.d. - - −7.44±0.19 37 150±9.4
a

Refer to Table 1 for the structure of the peptides.

b

Carried out using membrane preparations from transfected HN9.10 cells that constitutively expressed the respective opioid receptor type.

c

Kd = 0.50 ± 0.1 nM.

d

Kd = 0.85 ± 0.2 nM.

e

Logarithmic values determined from the non-linear regression analysis of data collected from at least 2 independent experiments.

f

Caculated using the Cheng and Prusoff equation to correct for the concentration of the radioligand used in the assay.

g

Logarithmic values determined from the non-linear regression analysis of data collected from at least 2 independent experiments. The EC50 value is converted from the respective log EC50.

h

[35S]GTP-γ-S bound / basal [35S]GTP-γ-S bound] X 100 ± standard error. n.c. incomplete competition of the radioligand at the highest test concentration of the peptide. An IC50 value cannot be determined. n.s. non-saturable dose-response curve. In these cases,stimulation of [35S]GTP-γ-S binding was observed only at the highest test dose(s) of the peptide (1 ×10−5 and 1 × 10−4 M). An EC50 or Emax value cannot be determined. n.d. not determined.