PROJECT SUMMARY/ABSTRACT
Opioid analgesics are critical for acute and chronic pain management, but important side effects limit their safety
and utility, including tolerance, constipation, respiratory depression, and abuse liability. We have determined that
simultaneous activation of µ-opioid receptors (MORs), with the opioid analgesic morphine, and enhancement of
GABAergic signaling at α2 and α3 subunit-containing GABAA (α2/α3GABAA) receptors, with the novel
imidazodiazepine ligand MP-III-024, produces synergistic antinociceptive and anti-hyperalgesic effects.
Preliminary data also indicate that MP-III-024/morphine mixes produce sub-additive effects in behavioral tests
sensitive to morphine side effects, supporting further investigation of a dual pharmacological approach that
simultaneously targets MOR and α2/α3GABAA to enhance analgesic effects without increasing side effects. We
hypothesize that this dual pharmacology approach will result in more effective antinociception with reduced
development of critical opioid side effects. To test this hypothesis, we will perform a comprehensive preclinical
analysis of the effects of dual MOR-α2/α3GABAA pharmacotherapy in models of pain, tolerance, constipation,
respiratory depression, and abuse liability. We will systematically test whether κ-opioid receptors or δ-opioid
receptors also contribute to the antinociceptive effects of MP-III-024/morphine mixtures. Finally, we will
determine whether bivalent ligands designed to simultaneously target MOR and α2/α3GABAA will produce
analgesic effects and represent a new line of medication development. If successful, these studies would identify
a new method to enhance opioid analgesia, requiring lower necessary doses of opioid medications, in turn
reducing the likelihood of dangerous side effects or the development of opioid dependence and addiction.