I am currently a senior level postdoctoral fellow with a primary research focus in opioid receptor pharmacology. I intend to transition to a junior faculty position in the next two years, and my current mentored position has been structured to accomplish this goal. I have a wide-range of experience with in vivo models of pain and addiction, as well as extensive experience with techniques to assess receptor binding, function, and localization ex vivo. I am currently working in the laboratory of Dr. Christopher Evans, a prominent opioid researcher, at the University of California Los Angeles (UCLA). During my time at UCLA, I will enhance my skill set by learning new techniques in primary cell culture, electrophysiology, and arrays. My mentor and I have also planned several strategies to facilitate my transition to a faculty position, including budgetary responsibility, teaching, and course work. UCLA is a renowned institution with a number of high profile researchers, and during this mentored phase I will develop important collaborations that I hope to sustain into my independence. In addition, the university also has several state-of-the-art core facilities through which I will enhance my research opportunities. My research focus is on the in vivo consequences of ligand directed signaling at the delta (4) opioid receptor. Agonists for this receptor are being developed for clinical use, as activation of 4 receptors relieves pain, and reduces anxiety and depression. However, a major limitation to the clinical use of these compounds is that a subset of 4 agonists also produce convulsions, the mechanism of which is unknown. This agonist-selective behavior could be due to differential trafficking and signaling of the 4 receptor, and my recent work shows that the internalizing agonist, SNC80, produces convulsions which are not observed with the non-internalizing agonist, ARM390. 2-arrestins are major mediators of receptor internalization, and also mediate subsequent receptor signaling. One of the aims of this proposal is to determine the role of 2-arrestins in SNC80 and ARM390-induced behaviors, using 2-arrestin 1 and 2 knockout mice. In addition, to characterize the different signaling mechanisms regulating this functional selectivity, the distinct signaling complexes formed by SNC80 and ARM390 will be determined using proximity ligation assays and phosphoprotein arrays. Furthermore, I have found that repeated use of these agonists in an inflammatory pain model also results in differential tolerance. SNC80 produces receptor down regulation and generalized tolerance to all agonist-induced effects. In contrast, ARM390-tolerant animals show intact 4 receptors, and analgesic tolerance only - the mechanism of which is unknown. A further aim of this application is to characterize this differential tolerance, by looking for changes in receptor-ion channel coupling within the dorsal root ganglia following chronic use. I will also examine the role of 2-arrestins in these two types of tolerance, and explore possible mechanisms underlying these differences using DNA microarrays. This work has important therapeutic implications, and will enhance our understanding of in vivo opioid receptor trafficking and signaling.

Public Health Relevance

Delta opioid receptor activation produces pain-relief, and reduces anxiety and depression;and for this reason agonist to this receptor are being developed for clinical use. However, a deterrent to the development of these compounds is that some delta agonists also produce convulsions, and at the moment there is no way to predict whether a novel agonist will have this property. The goal of this proposal is to determine the mechanism that accounts for this difference between agonists that bind to the same receptor. Ultimately, this work would increase the potential for the delta opioid receptor as a novel drug therapy.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Career Transition Award (K99)
Project #
5K99DA031243-02
Application #
8248182
Study Section
Human Development Research Subcommittee (NIDA)
Program Officer
Sorensen, Roger
Project Start
2011-04-01
Project End
2013-03-31
Budget Start
2012-04-01
Budget End
2013-03-31
Support Year
2
Fiscal Year
2012
Total Cost
$158,544
Indirect Cost
$11,744
Name
University of California Los Angeles
Department
Psychiatry
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Pradhan, Amynah A; Smith, Monique L; McGuire, Brenna et al. (2014) Characterization of a novel model of chronic migraine. Pain 155:269-74
Pradhan, Amynah A; Smith, Monique L; Zyuzin, Jekaterina et al. (2014) ?-Opioid receptor agonists inhibit migraine-related hyperalgesia, aversive state and cortical spreading depression in mice. Br J Pharmacol 171:2375-84
Pradhan, Amynah; Smith, Monique; McGuire, Brenna et al. (2013) Chronic inflammatory injury results in increased coupling of delta opioid receptors to voltage-gated Ca2+ channels. Mol Pain 9:8
Pradhan, Amynah A; Befort, Katia; Nozaki, Chihiro et al. (2011) The delta opioid receptor: an evolving target for the treatment of brain disorders. Trends Pharmacol Sci 32:581-90