HARNESSING NEURON TYPE-SPECIFIC GPCR TARGETS AND TOOLS FOR PRECISION ANALGESIA

Opioid analgesics are broadly used to manage severe pain, however they are responsible for harmful side effects, like addiction, hyperalgesia, constipation, and lethal opioid-induced respiratory depression (OIRD). Today, over 20% of the US population experiences chronic pain, with 1.6 million of the population having an opioid use disorder in the past year. This dual epidemic of chronic pain and opioid misuse urgently requires a better understanding of opioid receptor neurobiology and novel pharmacological targets to develop safer therapeutic alternatives to treat pain. In this dissertation work, I aimed to 1) uncover novel G protein-coupled receptor (GPCR) therapeutic targets that mediate non-opioid analgesia and 2) characterize the neuron type-specific dynamics of opioid receptors, to enable safer, precision analgesia. First, I describe the pharmacological targeting of non-opioid analgesic GPCRs that are expressed in neurons encoding the negative emotional valence of pain (i.e., pain unpleasant quality). Our lab previously described a discrete ensemble of neurons in the amygdala that encodes pain unpleasantness. We revealed several non-opioid GPCR targets enriched in these amygdalar neurons through single cell RNA sequencing (scRNA-seq), which individually decreased pain when targeted through systemic administration of selective ligands. By taking different pharmacological approaches, including allosteric receptor modulation and synergistic agonism, we demonstrated a decrease in pain affective-motivational behaviors in several preclinical pain assays, with limited side effects. Then, I outline the process of uncovering opioid receptor dynamics and interactomes across intact neural populations. Recent advances in in situ proximity labeling have enabled the neuro type-specific interrogation of receptor proteomes and ultrastructural localizations with high spatial and temporal resolution. I describe the development and use of novel adeno-associated viruses (AAVs) expressing ascorbate peroxidase 2 (APEX2)-conjugated opioid receptors in a Cre recombinase-dependent manner to uncover receptor interactions and trafficking across opioid receptor subtypes in a discrete neuronal population that co-express different types of opioid receptors. The interrogation of pharmacological targets and tools in this dissertation enables the discovery of analgesic alternatives to opioids, contributing to efforts that aim to end the current dual epidemic of chronic pain and OUD.