Role of an arousal circuit in respiration and opioid-induced respiratory depression

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PROJECT SUMMARY This K99/R00 Pathway to Independence Award is designed to allow the candidate to achieve her long-term goal to establish an independent research career focused on how arousal circuits in the brain control breathing, and how these neural mechanisms are influenced by opioids. This proposal has been tailored to supplement the candidate’s background in neuroscience and respiratory neurophysiology with additional knowledge and technical skills to study respiratory control circuits in vivo and ex vivo, and will make her ideally suited to succeed on her career path. The primary cause of death from an opioid overdose is respiratory depression. The sedative effect of opioids further impairs respiratory drive through largely unexplored mechanisms. Although overdoses are routinely treated with the opioid antagonist, naloxone, naloxone reverses all opioid effects, causing pain and withdrawal. Our current understanding of opioid effects on the respiratory circuitry has not revealed an ideal therapeutic target to minimize respiratory depression without serious side effects. Therefore, it is essential to identify new strategies to alleviate respiratory depression and stimulate breathing. This proposal seeks to uncover important new insights whereby the locus coeruleus (LC), a brain structure widely known for its contributions to arousal, influences the Kӧlliker-Fuse (KF), a key respiratory region, which is highly sensitive to opioids and critical for opioid-induced respiratory depression. Preliminary data spanning cell-type specific neural tracing, ex vivo brain slice recordings, and in vivo optogenetics and fiber photometry, support a role for LC input to the KF in respiration, which has not been previously appreciated. Based on preliminary data, the overall hypothesis is that the LCKF circuit is a critical modulator of respiratory function, particularly during opioid-induced respiratory depression. The candidate’s prior training in brain slice recordings, in vivo electrophysiology in awake animals, and intersectional viral- genetic methods provides a solid foundation for the state-of-the-art ex vivo and in vivo optogenetics and fiber photometry techniques in the proposal. This multi-level approach will allow the candidate to test the hypothesis that KF neurons receive opioid-sensitive, monosynaptic excitatory input from LC neurons (Aim 1), that KF projecting LC neuron activity is coupled with respiration in vivo (Aim 2), and the LCKF circuit plays a key role in respiration and opioid-induced respiratory depression (Aim 3). Together, the aims of this proposal will yield novel information regarding the brain’s control of respiration and will also provide strong conceptual and methodological training, enabling development of an impactful and successful independent research program. Strong mentorship by Drs. Erica Levitt and David Fuller, as well as a Mentoring Committee comprised of established professors, who are experts in the proposed techniques and have extensive mentoring experience, will help the candidate achieve the research and career development goals of this proposal.