【Customer Case】Application of Whole Body Plethysmography System in Sleep Research

CeA SST+ Neurons Regulate Stress-Induced Insomnia

Research Overview

Recently, a research team led by Li Chen from the Fujian Key Laboratory of Drug Target Discovery and Structural and Functional Research, Department of Pharmacology, School of Pharmacy, Fujian Medical University, published a study titled "Central amygdala somatostatin neurons modulate stress-induced sleep-onset insomnia" in Communications Biology.

Application of WBP

In this study, the team utilized WBP-4M (a whole-body plethysmography system for mice independently developed by TOW-INT TECH) to monitor respiratory parameters. Specifically, under anesthesia, tidal volume (Vt) and respiratory rate were recorded in mice. Blue light stimulation (10 ms, 30 Hz, 3–5 mW/mm², 1 min) was applied to activate somatostatin-positive (SST+) neurons in the central amygdala (CeA) to observe their impact on respiratory frequency.
Results revealed that activating CeA SST+ neurons significantly increased respiratory rate (control: 87.8 ± 6.537 breaths/min → post-stimulation: 106.7 ± 6.926 breaths/min). This indicates that CeA SST+ neurons not only regulate anxiety-like behaviors and sleep-wake transitions but also modulate stress-related physiological metrics (e.g., respiratory rate), further supporting their critical role in stress-induced sleep disorders.

Experimental Methods
1. Fiber Photometry
   - Recorded Ca²⁺ dynamics of CeA SST+ neurons under stressors (restraint, rat bedding, air puff, cage change).
   - Neurons were labeled using Cre-dependent AAV-GCaMP7s, and fluorescence signals were monitored via optical fibers.

2. Optogenetics
   - Expressed ChR2 in CeA SST+ neurons of SST-Cre mice. Acute or semi-chronic activation (20 Hz blue light) was used to assess sleep-wake transitions.
   - Combined EEG/EMG recordings analyzed sleep stages (latency and probability of NREM→wake transitions).

3. Chemogenetics
   - Employed DREADD technology (hM3Dq activation and hM4Di inhibition) to chronically modulate CeA SST+ neuronal activity, evaluating effects on sleep latency and architecture.

4. Behavioral and Physiological Analyses
   - Open Field Test (OFT) & Elevated Plus Maze (EPM): Assessed anxiety-like behaviors.
   - WBP-4M: Recorded respiratory rate and tidal volume under optogenetic stimulation.
   - Pupillometry: Quantified pupil dilation during CeA SST+ neuron activation.

5. Stress Models
   - Cage Change Challenge: Mimicked the "first-night effect" by transferring mice to a cage previously inhabited by other mice.
   - Restraint Stress: Restricted mouse movement for 1 hour to induce sleep-onset difficulties.

6. Immunohistochemistry
   - Detected c-fos expression to validate neuronal activation and confirmed SST+ neuron specificity via SST antibody labeling.
Experimental Results
1. CeA SST+ Neuronal Responses to Stress
   - Multiple stressors (restraint, rat bedding, air puff, cage change) significantly increased Ca²⁺ activity in CeA SST+ neurons (e.g., ΔF/F rose from 4.5% to 17.5% post-cage change).

2. Optogenetic Activation Effects
   - Acute activation (20 Hz blue light) shortened NREM→wake latency to 11.6 seconds (vs. control: 60 seconds) with 100% transition probability.
   - Semi-chronic activation (1 hour) prolonged sleep latency (35.05 min vs. control: 1.56 min) and increased wake duration (51.19 min vs. 21.20 min).

3. Chemogenetic Modulation
   - Activation (CNO treatment) extended sleep latency to 69.6 minutes (vs. control: 18.5 minutes), while inhibition alleviated stress-induced insomnia (latency reduced from 51 to 27 minutes).
   - Inhibiting CeA SST+ neurons did not alter physiological sleep architecture, indicating specificity to stress-induced insomnia.


4. Behavioral and Physiological Changes
   - CeA SST+ neuron activation induced anxiety-like behaviors (reduced center time in OFT, increased closed-arm time in EPM) and elevated respiratory rate (106.7 vs. baseline: 87.8 breaths/min).

Research Conclusions
By integrating multimodal approaches, the team concluded:
1. CeA SST+ neurons are key regulators of stress-induced sleep-onset insomnia. These neurons are activated under stress, promoting wakefulness and prolonging sleep latency.
2. Target specificity: Inhibiting CeA SST+ neurons alleviated stress-related insomnia without disrupting normal sleep, highlighting their therapeutic potential.
3. Neural mechanism hypothesis: CeA SST+ neurons may regulate sleep-wake balance by suppressing downstream sleep-promoting regions (e.g., vIPAG NTS+ neurons) or integrating upstream stress signals (e.g., PVT, VTA inputs).
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References

[1]Yao W, Huang S X, Zhang L, et al. Central amygdala somatostatin neurons modulate stress-induced sleep-onset insomnia[J]. Communications Biology, 2025, 8(1): 381.