Defense Date


Document Type


Degree Name

Doctor of Philosophy


Pharmacology & Toxicology

First Advisor

Matthew Banks

Second Advisor

Sidney Negus

Third Advisor

Katherine Nicholson

Fourth Advisor

Kimberle Jacobs

Fifth Advisor

Pamela Knapp


Mu-opioid receptor (MOR) agonists are effective agents for pain management, but are also limited by a number of undesirable effects. One approach to enhance the therapeutic effects and minimize the undesirable effects of MOR agonists may be to combine MOR agonists with an adjunct targeting a different receptor system. This targeted medical approach, known as “combination therapy”, aims to augment the desired effects of the MOR agonist (i.e. antinociception) and/or diminish the undesirable deleterious side effects of the MOR agonist. This dissertation investigated the utility of this approach in an assay of thermal nociception and schedule-controlled responding in male rhesus monkeys with three aims. One aim determined the utility of N-methyl D-aspartate (NMDA) receptor antagonists to selectively enhance MOR agonist antinociception. A second identified the pharmacological determinants of antinociceptive interactions between a nociceptin opioid peptide (NOP) receptor agonist and MOR agonists. A third aim investigated the potential for fixed-proportion mixtures of a competitive MOR antagonist and MOR agonist to manipulate antinociceptive efficacy. Experimental results did not support the utility of NMDA antagonists as adjuncts to selectively enhance MOR agonist antinociception. Furthermore, the antinociceptive interactions between a NOP agonist and MOR agonists were modest and occurred under a narrow range of conditions. Finally, fixed proportion MOR antagonist-agonist mixtures were effective in manipulating antinociceptive in vivo efficacy. In conclusion, this dissertation does not provide strong empirical evidence that a combination therapy approach will result in clinically effective and selective enhancement of MOR agonist analgesia. The dissertation concludes with proposed strategies and novel preclinical methods to enhance preclinical-to-clinical translation of effective candidate analgesics.


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