PAIN-ACTIVE CENTROLATERAL THALAMUS NEURONS PROJECTING TO ANTERIOR CINGULATE CORTEX MEDIATE PAIN-INDUCED SLEEP DISRUPTION IN MICE

Chronic pain and sleep disruption form a bidirectional cycle, yet the neural circuits driving pain-induced sleep fragmentation remain unknown. The centrolateral thalamus (CL), an intralaminar nucleus involved in arousal and nociception, projects densely to the anterior cingulate cortex (ACC), a region critical for affective pain processing and slow-wave generation and transmission during NREM sleep. We hypothesized that pain-active CL→ACC neurons mediate pain-induced sleep disruption. To test necessity, we used activity-dependent labeling (TRAP2) combined with viral Kir2.1 overexpression to constitutively inhibit pain-active CL neurons in mice with chronic neuropathic pain. To test sufficiency, we expressed excitatory DREADDs (hM3Dq) in pain-responsive CL→ACC neurons using an intersectional viral approach and activated them for seven consecutive days. Sleep-wake behavior was assessed via automated home-cage activity monitoring. Inhibition of pain-active CL neurons prevented mechanical hypersensitivity and preserved rest bout duration. Conversely, chemogenetic activation of CL→ACC neurons decreased rest bout duration without altering mechanical sensitivity. These results demonstrate that pain-active CL→ACC neurons are both necessary and sufficient for pain-induced sleep disruption. To investigate neural dynamics preceding these arousals, we developed a multimodal platform combining miniscope calcium imaging in ACC, local field potential recordings in CL and ACC, polysomnography, electrocardiography, and LUPE, the in-house developed deep-learning behavioral tracking. We identified two distinct awakening types: pain-triggered arousals, characterized by spontaneous pain behaviors immediately following sleep-wake transitions, and non-pain-triggered arousals. Current analyses are comparing CL and ACC activity patterns preceding each awakening type to determine how pain alters thalamocortical circuits to fragment sleep.