Identification of a Circuit Basis for Neuropathic Pain in the Parabrachial Nucleus - Project Summary / Abstract The parabrachial nucleus (PBN) serves as a crucial nexus where nociceptive sensory signals from the spinal cord are transformed into the unpleasant components of pain. Persistent forms of pain such as neuropathic pain result in hyperexcitation of a subset of PBN neurons, which is thought to underlie heightened pain perception. Furthermore, inhibiting PBN activity is sufficient to restore normal pain levels or prevent the development of neuropathic pain altogether, highlighting the PBN as a potent therapeutic target for pain management. However, the PBN is composed of dozens of transcriptionally defined cell types involved in diverse functions (e.g., pain, malaise, breathing), making it challenging to manipulate the PBN without affecting other behaviors. Ideally, future therapeutic strategies could be designed to inhibit those PBN neurons that contribute to increased pain, while sparing others. This would require answering the following fundamental questions about PBN: (i) How are different pain-related stimuli integrated in the PBN? (ii) Do specific subtypes of PBN neurons become hyperexcitable during neuropathic pain states? (iii) Is inhibiting pain-responsive PBN subtypes sufficient to induce analgesia? The main barrier to answering these questions is the lack of tools to link functional and transcriptomic information in individual neurons. I have recently overcome this barrier by developing a 3D imaging pipeline to track the activity of hundreds (in vivo) to thousands (ex vivo) of PBN neurons followed by multiplexed mRNA labeling of dozens of genetic markers in each imaged neuron. The studies and career development activities in this K99/R00 proposal are designed to provide me with the necessary training to initiate an independent research program that applies these new tools to the study of neuropathic pain in PBN. I hypothesize that the PBN subtypes that become hyperexcitable during neuropathic pain will emerge as potent targets for analgesic interventions while minimizing undesired effects on other physiological functions. This proposed research endeavor will benefit from the mentorship of Drs. Mark Andermann, Brad Lowell, and Clifford Woolf, experts in in vivo imaging, PBN circuitry, and pain, respectively. Dr. Woolf's laboratory will provide training in pain assays, as well as surgical induction of neuropathic pain, while the Lowell lab will train me in transcriptomic data analysis and the generation of transgenic mouse lines. Additionally, my advisory committee, comprising Drs. Alexander Banks, Yuhan Wang, Gregory Corder, and Maria Lehtinen, will offer specialized training in metabolic cage recordings, advanced in situ hybridization methods, in vivo imaging during pain, and intracerebral drug infusions. Beyond technical mentorship, my mentors and advisory committee members are committed to equipping me with the necessary skills for a seamless transition to an independent investigator.
