Fentanyl produced rapid, ensemble-wide reconfiguration of multimodal afferent encoding in the NTS of anesthetized mice, altering how cardiorespiratory signals are interpreted.
Opioids profoundly disrupt breathing, yet the network-level mechanisms within the nucleus tractus solitarius (NTS), the brainstem hub for integrating cardiorespiratory afferents, remain poorly understood. Using high-density Plexon SiNAPS recordings in anesthetized mice, we simultaneously measured neuronal activity in the NTS alongside respiratory airflow, diaphragm EMG, end-tidal CO 2 , carotid pulse pressure, and ECG. We developed an analysis framework combining (1) breath- and cardiac-aligned spike timing, (2) spike-triggered averages, and (3) a Poisson generalized linear model (GLM) to quantify how individual neurons encode respiratory phase, respiratory drive, blood pressure, CO 2 , and cardiac phase. Across NTS units, we found highly heterogeneous but structured multimodal encoding, with most neurons driven by multiple afferent inputs. ΔR 2 variance partitioning revealed distinct encoding signatures that mapped onto functional clusters identified via UMAP + HDBSCAN. Importantly, fentanyl produced rapid, ensemble-wide reconfiguration. Some NTS neuron clusters were silenced, others were strongly excited, and a subset showed preserved firing but altered encoding weights, particularly in respiratory-phase and pressure-related kernels. Despite large drug-induced changes in ventilation and autonomic output, our GLM analyses show that the structure of afferent encoding, not just firing rate, changes during opioid exposure, indicating that opioids reshape how the NTS interprets cardiorespiratory signals. These findings support a model in which opioid-induced dysregulation of NTS afferent integration contributes to failures of compensatory homeostatic reflexes during opioid overdose. Together, these data provide a high-dimensional map of multimodal encoding in the NTS during opioid perturbation and establish a framework for identifying neural substrates of respiratory and autonomic collapse. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Andersen et al. (Fri,) conducted a other in Opioid exposure. Fentanyl was evaluated on Neuronal encoding of respiratory phase, respiratory drive, blood pressure, CO2, and cardiac phase. Fentanyl produced rapid, ensemble-wide reconfiguration of multimodal afferent encoding in the NTS of anesthetized mice, altering how cardiorespiratory signals are interpreted.