| Studies of mu-, kappa-, and delta-Opioid Receptor Densities and G Protein Activation in Cerebral Membranes of Mice. |
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Hee Seung Lee |
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Department of Anesthesiology and Pain Medicine, College of Medicine, Ewha Womans University, Seoul, Korea. leehee@ewha.ac.kr |
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| Abstract |
BACKGROUND
The aim of this study was to investigate the relative densities of mu-, kappa-, and delta-opioid receptors (MOR, KOR, and DOR) and [35S]GTPgammaS binding as stimulated by full agonists in mouse cerebral membranes METHODS: Naive mice (ICR, male, n = 20) were euthanized for cerebral membrane preparation. For saturation binding, [3H]DAMGO, [3H]U69593, and [3H]DPDPE were used to determine the binding parameters [Bmax (femtomoles per milligram)/Kd (nanomolar)]. And, for [35S]GTPgammaS stimulation binding, DAMGO, U69593, and SNC80 were used to determine EC50 (nanomolar) and maximum stimulation (% over basal) for MOR, KOR, and DOR, respectively. The Ke values of the corresponding selective antagonist, naloxone (20 nM), nor-BNI (3 nM), and naltrindole (3 nM) were also calculated.
RESULTS
The values of Bmax and Kd for saturation binding were as follows: [3H]DAMGO (MOR; 56.4/0.92), [3H]U69593 (KOR; 23.6/1.66), and [3H]DPDPE (DOR; 71.4/3.12), and the relative proportions of MOR, KOR, and DOR were 37.3, 15.6, and 47.2%. The EC50, maximum stimulation, and the Ke value of [35S]GTPgammaS binding were as follows: DAMGO (MOR; 215.3/18.3/2.10), U69593 (KOR; 38.5/8.9/0.32), and SNC80 (DOR; 84.3/28.3/0.36). Bmax and maximum [35S]GTPgammaS binding stimulation were linearly correlated (r = 0.99).
CONCLUSIONS
The densities of three opioid receptors were found to be significantly different in mouse cerebral membrane. The amount of G protein activated by agonists were found to be directly proportional to relative receptor density. |
| Key Words:
cerebrum; gtp binding; mice; opioid receptor |
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