This project is a novel investigation of opioid receptors in amphibians. The overall objective is to examine the antinociceptive action of opioids in amphibian as an evolutionary model that will provide insights into the action of opioids in the clinic and on the street. The premise is that understanding the mechanisms of opioid receptor selectivity and activation in earlier-evolved vertebrates will help in the design and understanding of opioid action in humans. Morphine and other opioid drugs produce analgesia in humans and antinociception in animals by direct interaction with opioid receptor proteins located on neurons in the brain and spinal cord. Knowledge of the detailed relationship between the molecular structure of the opioid drug and the molecular conformation of the opioid receptor is essential to understand pharmacological actions of opioids. Whereas mammalian CNS expresses three distinct opioid receptor genes (MOR1, DOR1, KOR1), each capable of mediating antinociception mammals, amphibians appear to mediate the antinociception effects ofmu, 8, and K-selective opioid agonists via a single opioid receptor, termed the 'unireceptor'. Brain and spinal cord tissue homogenates from the Northern grass frog, Rana pipiens, will be used for all studies.
The specific aims are: 1) Determine the affinity, receptor density, and selectivity of sites labeled with ji-, K-, S-selective opioid radioligands; 2) Determine affinity, receptor density, and selectivity of sites labeled with highly-selective mu-, K-, delta-opioid antagonist radioligands; and 3) Characterize the intrinsic activity and selectivity of mu-, K-, S-selective opioid agonists by the stimulation of GTPTS35 binding. Preliminary data are presented for each of these specific aims. Additionally as our lab is the sole purveyor of opioid pharmacology using an earlier-evolved vertebrate model, the proposed studies are a unique examination of the functional evolution of opioid receptors. These studies challenge existing paradigms and further develop a new methodology for the study of opioids. Data obtained will be significant contributions to current understanding of the functional evolution of opioid receptors with regard to opioid ligand selectivity. This knowledge will likely contribute to the to understanding of the mechanisms of opioid receptor activation and may help guide the rational development of improved therapies where opioids drugs are used or abused.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Academic Research Enhancement Awards (AREA) (R15)
Project #
5R15DA012448-03
Application #
6515683
Study Section
Integrative, Functional and Cognitive Neuroscience 8 (IFCN)
Program Officer
Thomas, David A
Project Start
1999-06-01
Project End
2004-08-31
Budget Start
2002-07-01
Budget End
2004-08-31
Support Year
3
Fiscal Year
2002
Total Cost
$72,800
Indirect Cost
Name
Osu Center of Health Sciences
Department
Pharmacology
Type
Schools of Osteopathy
DUNS #
City
Tulsa
State
OK
Country
United States
Zip Code
74107
Stevens, Craig W (2015) Bioinformatics and evolution of vertebrate nociceptin and opioid receptors. Vitam Horm 97:57-94
Stevens, Craig W (2011) Analgesia in amphibians: preclinical studies and clinical applications. Vet Clin North Am Exot Anim Pract 14:33-44
Mohan, Shekher; Davis, Randall L; DeSilva, Udaya et al. (2010) Dual regulation of mu opioid receptors in SK-N-SH neuroblastoma cells by morphine and interleukin-1ýý: evidence for opioid-immune crosstalk. J Neuroimmunol 227:26-34
Stevens, Craig W (2009) The evolution of vertebrate opioid receptors. Front Biosci (Landmark Ed) 14:1247-69
Stevens, Craig W; Martin, Kristin K; Stahlheber, Brad W (2009) Nociceptin produces antinociception after spinal administration in amphibians. Pharmacol Biochem Behav 91:436-40
Davis, Randall L; Buck, Daniel J; Saffarian, Neda et al. (2008) Beta-funaltrexamine inhibits inducible nitric-oxide synthase expression in human astroglial cells. J Neuroimmune Pharmacol 3:150-3
Brasel, Chris M; Sawyer, Gregory W; Stevens, Craig W (2008) A pharmacological comparison of the cloned frog and human mu opioid receptors reveals differences in opioid affinity and function. Eur J Pharmacol 599:36-43
Davis, Randall L; Buck, Daniel J; Saffarian, Neda et al. (2007) The opioid antagonist, beta-funaltrexamine, inhibits chemokine expression in human astroglial cells. J Neuroimmunol 186:141-9
Stevens, Craig W; Toth, Geza; Borsodi, Anna et al. (2007) Xendorphin B1, a novel opioid-like peptide determined from a Xenopus laevis brain cDNA library, produces opioid antinociception after spinal administration in amphibians. Brain Res Bull 71:628-32
Newman, Leslie C; Sands, Steven S; Wallace, David R et al. (2002) Characterization of mu, kappa, and delta opioid binding in amphibian whole brain tissue homogenates. J Pharmacol Exp Ther 301:364-70

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