Long-term imaging of dorsal root ganglia in awake behaving mice

• Published in: Nature communications 2019-07, Vol.10 (1), p.3087-11, Article 3087
• Main Authors: Chen, Chao, Zhang, Jinhui, Sun, Linlin, Zhang, Yiling, Gan, Wen-Biao, Tang, Peifu, Yang, Guang
• Format: Article
• Language: English
• Subjects: 14; 14/69; 631/1647/245; 631/1647/245/2225; 631/378/1959/2605; 631/378/3917; 64/60; 82/51; Anesthesiology; Animal behavior; Animals; Behavior Observation Techniques - instrumentation; Behavior Observation Techniques - methods; Behavior, Animal - physiology; Calcium; Calcium - chemistry; Calcium imaging; Dorsal root ganglia; Female; Formaldehyde; Formaldehyde - administration & dosage; Formaldehyde - toxicity; Ganglia; Ganglia, Spinal - cytology; Ganglia, Spinal - diagnostic imaging; Ganglia, Spinal - physiology; Green Fluorescent Proteins - chemistry; Green Fluorescent Proteins - genetics; Hospitals; Humanities and Social Sciences; Hyperactivity; Imaging; Implantation; In vivo methods and tests; Injection; Intravital Microscopy - instrumentation; Intravital Microscopy - methods; Male; Mice; Mice, Transgenic; Models, Animal; multidisciplinary; Neurons; Optical Imaging - instrumentation; Optical Imaging - methods; Orthopedics; Pain; Pain - chemically induced; Pain - physiopathology; Pain Perception - physiology; Photons; Science; Science (multidisciplinary); Sensory neurons; Sensory perception; Sensory Receptor Cells - physiology; Spinal cord; Surgery; Surgical implants; Surgical outcomes; Vertebrae; Wakefulness
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-11158-0

The dorsal root ganglia (DRG) contain the somas of first-order sensory neurons critical for somatosensation. Due to technical difficulties, DRG neuronal activity in awake behaving animals remains unknown. Here, we develop a method for imaging DRG at cellular and subcellular resolution over weeks in awake mice. The method involves the installation of an intervertebral fusion mount to reduce spinal movement, and the implantation of a vertebral glass window without interfering animals’ motor and sensory functions. In vivo two-photon calcium imaging shows that DRG neuronal activity is higher in awake than anesthetized animals. Immediately after plantar formalin injection, DRG neuronal activity increases substantially and this activity upsurge correlates with animals’ phasic pain behavior. Repeated imaging of DRG over 5 weeks after formalin injection reveals persistent neuronal hyperactivity associated with ongoing pain. The method described here provides an important means for in vivo studies of DRG functions in sensory perception and disorders. Imaging sensory neurons in the dorsal root ganglion (DRG) in awake animals is challenging due to motion artefacts and other technical issues. Here the authors develop an intervertebral fusion procedure which minimizes spinal movement thereby enabling chronic imaging of DRG neurons in awake, behaving mice.