Noradrenergic mechanisms underlying stress-induced opioid reinstatement - PROJECT SUMMARY The initiating factor for opioid use disorder often stems from comorbid neuropsychiatric conditions including anxiety, depression, and post-traumatic stress disorder. Experience of extreme or traumatic stress is often the underlying factor responsible for these neuropsychiatric conditions and, thus, investigation into the neural mechanisms by which stress impacts the brain is essential for determining the mechanisms responsible for the initiation of substance use disorders. Our preliminary data demonstrates that stress exposure leads to increased cytokine release and heightened activity of the noradrenergic locus coeruleus (LC), a key region responsible for the integration of stress signaling that projects norepinephrine to numerous downstream brain areas. The prelimbic cortex of the medial prefrontal cortex (PrL) is one such region that receives over 90% of its noradrenergic innervation from the LC and plays a major role in drug seeking and reward-related behaviors. Thus, the overall goal of this project is to establish the circuit mechanisms of stress-related norepinephrine release in the PrL and the role of these projections in oral oxycodone seeking behaviors. These experiments will use cutting edge techniques including chemogenetics, in vivo electrophysiology, and fiber photometry with GRAB sensors to monitor neuronal activity and transmitter release across this circuit in response to stress and drug stimuli. Three main experiments have been designed to address the hypothesis that stress-evoked increases in neuroimmune activity in the LC initiate neuronal activation and downstream NE release to mediate stress- induced drug seeking behavior. First, chemogenetic suppression of neuroimmune activity in the LC will be paired with in vivo electrophysiology during stress to monitor the impact of microglial reactivity on neuronal activity within this region (Aim1, K99). The second experiment will utilize GRABNE sensors in the PrL to determine the time-course of norepinephrine release in response to stress cues. These studies will also use adrenergic receptor antagonists microinjected into the PrL during stress-cue reinstatement to determine the mechanisms by which NE is acting in this region to impact drug seeking behaviors (Aim2, K99). The final experiment will use translationally relevant compounds to determine if the reversal of stress-induced neuroimmune reactivity can prevent the deleterious effects observed as a consequence of stress (Aim3, R00). Taken together, these studies will expand our understanding of the circuit mechanisms responsible for stress-related opioid seeking behaviors and determine the therapeutic potential of clinically available pharmaceuticals all while providing extensive training in innovative preclinical techniques. The combined technical training and career development opportunities supported by this application will facilitate further independent projects designed to address unanswered questions regarding the neural mechanisms responsible for opioid use to develop novel treatment targets for comorbid stress and substance use disorders.
