Semester

Spring

Date of Graduation

2019

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Physiology, Pharmacology & Neuroscience

Committee Chair

Bernard Schreurs

Committee Co-Chair

David Siderovski

Committee Member

David Siderovski

Committee Member

Vincent Setola

Committee Member

Walter Byrd

Committee Member

Werner Geldenhuys

Abstract

Endogenous opioids mediate both analgesic and affective responses to stress. While the mu opioid receptor (MOR) produces the reinforcing euphoric effects responsible for the high abuse potential of traditional opioid analgesics, the kappa opioid receptor (KOR) is hypothesized to mediate the dysphoric component of stress. With increasing rates of opioid addiction, extensive research efforts are focused on better understanding each of these systems and how they interact, with the goal of developing less addictive pain management strategies and better approaches to addiction treatment. With this in mind, we conducted both clinical and pre-clinical studies aimed at developing better treatment strategies for opioid use and the management of patients with opioid use disorder (OUD). First, we assessed a local cohort of patients with (OUD) for a collection of single nucleotide polymorphisms (SNPs) related to reward processing, with the goal of furthering efforts to develop a gene-based screening mechanism for OUD risk assessment. Second, we conducted preclinical assessments of the G protein-biased KOR agonist nalfurafine as a potential adjuvant medication for increasing the therapeutic efficacy of opioid-based analgesia. Genetic analysis of OUD patients identified two SNPs within the gene encoding the mu opioid receptor, one SNP within the gene encoding the serotonin 2B (5-HT2B) receptor, and one SNP within the gene encoding Regulator of G protein Signaling 2 (RGS2), with the frequency of each SNP varying significantly from that observed in reference populations of European descent. Preclinical investigations with nalfurafine use in mice demonstrated a greater analgesic synergy when co-administered with morphine than morphine co-administered with the unbiased KOR agonist U50,488. As G protein-biased KOR agonists are hypothesized to produce less dysphoria (a therapeutically limiting side effect of KOR agonists), they may present a viable method for reducing the dose of MOR-targeting analgesic necessary for adequate pain relief, thereby reducing the likelihood of developing OUD. Further research is necessary to identify any anti-therapeutic effects of co-administering these two classes of drugs, as well as the range of pain modalities for which this approach is efficacious.

Download

Share

COinS