17: Longitudinal trigeminal ganglion sensory encoding in anesthetized, awake, and freely moving mice

Topic: Basic Science
Subtopic: Non-specific to any diagnosis (including studies in healthy animals), Developing methodology/technology, Pharmacological interventions, Animal imaging (includes Ca2+ imaging, fluorescence microscopy)

Background and Aims: The face is a key location for sensory processing across the animal kingdom. Trigeminal ganglion neurons (TGNs) process facial somatosensory information, transmitting it to the nucleus caudalis and then to the brain. This processing can become abnormal, as is thought to occur in trigeminal neuralgia, a devastating pain condition with significant need for treatment. Understanding how TGN computation relates to perception and behavior, along with how this changes in chronic pain and analgesic states, necessitates recording TGN activity over time and in behaving animals. To address these gaps, here we longitudinally imaged TGN activity in anesthetized and awake animals.

Methods: We developed a calcium imaging approach to longitudinally record TGNs. We expressed jGCaMP8 in sensory neurons and implanted a microendoscopic (GRIN) lens over the trigeminal ganglion, focusing on maxillary zone innervating TGNs. We imaged TGNs using one-photon microscopy, in either freely moving mice with miniature microscopes or head-fixed, and then processed and analyzed the imaging datasets using CIAtah (git.io/ciatah). We delivered mechanical, thermal, pruritic, gustatory, and other stimuli to the face or oral cavity. We measured face temperatures using thermal imaging. For awake mice, we concurrently monitored and quantified behavior using accelerometers and machine vision analysis.

Results: We monitored post-surgery animals for weeks to months and found that behavior recovered. In vivo microCT imaging validated GRIN lens placement. We identified stimulus-evoked TGN activity to orofacial ipsilateral—but not contralateral—thermal, mechanical (including whisker and oral cavity), and pruritogenic stimuli, in anesthetized and awake, behaving animals. We recorded stimulus-responsive TGNs, at times daily, for weeks to months post-surgery. Cross-session tracking revealed that certain TGNs preserved their coding properties for days. Facial nerve block eliminated TGN stimulus-evoked activity; crucially, activity returned the following day. In awake animals, TGN activity and behavior were at times decoupled depending on animal state.

Conclusions: Longitudinal imaging demonstrated that TGNs can stably encode sensory information that recovers after transient nerve block. With our approach we can monitor individual TGNs while relating TGN activity to behavioral outcomes after injury (e.g. persistent trigeminal pain and itch models) and analgesics (e.g. carbamazepine and novel compounds). We conducted hours-long TGN recordings in awake mice, allowing us to assess pharmacodynamics and -kinetics. We can now screen novel therapies for facial and dental pain. Our finding that TGN stimulus-evoked activity does not always correlate with behavior emphasizes the need to investigate the relationship between peripheral and central nervous system activity in awake animals.

References: CIAtah software: Corder, G., Ahanonu, B., Grewe, B.F., Wang, D., Schnitzer, M.J., Scherrer, G., 2019a. An amygdalar neural ensemble that encodes the unpleasantness of pain. Science 363, 276–281. https://github.com/bahanonu/ciatah.

Presenting Author: Biafra Ahanonu
Submitting Author: Biafra Ahanonu

Senior Author: Allan Basbaum

IASP 2026 Global Year theme of Neuropathic Pain: Yes

• Biafra Ahanonu: PhD - Stanford University
• Darian Mohsenin: BS - University of California, San Francisco
• Xiaobing Yu: MD - University of California, San Francisco
• Allan Basbaum: PhD - University of California, San Francisco