[Frontiers in Bioscience S2, 772-780, January 1, 2010]

Kappa2 opioid receptor subtype binding requires the presence of the DOR-1 gene

Michael A Ansonoff1, Ting Wen1, John E. Pintar1

1Department of Neuroscience and Cell Biology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School (UMDNJ-RWJMS), 675 Hoes Lane, Piscataway, NJ 08854

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and methods
3.1. Mice
3.2. Binding studies
3.2.1. Saturation studies
3.2.2. Displacement studies
3.3. Behavioral studies
3.4. Statistical analysis
4. Results
4.1. Confirmation of the existence of kappa2 opioid receptor binding
4.2. Knockout of DOR-1 gene eliminates kappa2 opioid receptor binding
4.3. Knockout of the DOR-1 gene increases kappa1 opioid receptor binding in spinal cord membranes
4.4. Knockout of the DOR-1 gene increases potency of intrathecally injected U69,593
4.5. Co-injection of kappa agonists with delta ligands enhances kappa agonist intrathecal potency
5. Discussion
6. Acknowledgements
7. References

1. ABSTRACT

Over the past several years substantial evidence has documented that opioid receptor homo- and heterodimers form in cell lines expressing one or more of the opioid receptors. We used opioid receptor knockout mice to determine whether in vivo pharmacological characteristics of kappa1 and kappa2 opioid receptors changed following knockout of specific opioid receptors. Using displacement of the general opioid ligand diprenorphine, we observed that occupancy or knockout of the DOR-1 gene increases the binding density of kappa1 receptors and eliminates kappa2 receptors in crude membrane preparations while the total density of kappa opioid binding sites is unchanged. Further, the analgesic potency of U69,593 in cumulative dose response curves is enhanced in mice lacking the DOR-1 gene. These results demonstrate that the DOR-1 gene is required for the expression of the kappa2 opioid receptor subtype and are consistent with the possibility that a KOR-1/DOR-1 heterodimer mediates kappa2 pharmacology.