The Science Behind Feeling Cold During a Fever
Ever wondered why a feverish body feels freezing cold, prompting us to bundle up under blankets? This counterintuitive sensation, known as chills, is the body's clever way of ramping up its temperature to fight infection. Researchers at Nagoya University in Japan have pinpointed the exact neural pathway responsible, revealing how chills actively support immune defense.
Fever, or pyrexia, occurs when the body's internal thermostat resets higher—typically to 38-40°C (100.4-104°F)—slowing pathogen replication and enhancing white blood cell function. Chills precede this rise, involving piloerection (goosebumps), shivering, and behavioral warmth-seeking. While autonomic mechanisms like shivering were known, the brain circuit for the subjective cold sensation remained elusive until this study.
The discovery highlights how prostaglandin E₂ (PGE₂), a lipid mediator produced by brain endothelial cells during infection, orchestrates both physiological and emotional responses. This dual action underscores fever as an adaptive strategy, not just a symptom.
Nagoya University's Research Team and Methods
Leading the effort was Professor Kazuhiro Nakamura from the Department of Integrative Physiology at Nagoya University Graduate School of Medicine. Collaborators included Dr. Takaki Yahiro (now at Oregon Health & Science University) and Dr. Yoshiko Nakamura. Nakamura's lab specializes in central neural circuits for thermoregulation, with prior breakthroughs on fever switches and thermosensory pathways.
Using male rats as a model—standard for neural circuit studies due to consistent responses—the team employed precise intracerebral injections. They targeted the lateral parabrachial nucleus (LPB), a brainstem relay for sensory signals. Rats underwent thermal plate preference tests (TPPTs): two adjacent plates at 28°C (neutral) and 39°C (warm). Normal rats favored neutral temperatures, but PGE₂-injected LPB-shifted preferences dramatically toward warmth, elevating core body temperature without shivering.
- Injection of PGE₂ analogs specific to EP1-4 receptors isolated EP₃ (prostaglandin E₂ receptor 3) as key.
- Tracing showed EP₃-expressing LPB neurons project mainly to the central amygdala (CeA), evoking discomfort.
- Cold exposure activated this pathway, confirming cold signal amplification.
Published in The Journal of Physiology (DOI: 10.1113/JP289466), the work was funded by Japan's Moonshot R&D and MEXT grants, showcasing national support for neuroscience.
Decoding the Neural Pathway Step by Step
The mechanism unfolds in precise sequence:
- Infection triggers immune cells to induce PGE₂ synthesis in brain vascular endothelium.
- PGE₂ diffuses to the preoptic area (POA) of the hypothalamus, the master thermoregulator, activating EP₃ neurons for autonomic fever: brown adipose tissue (BAT) thermogenesis, vasoconstriction, and eventual shivering.
- Simultaneously, PGE₂ reaches LPB glutamatergic neurons expressing EP₃ receptors.
- These neurons amplify incoming cold signals from spinal-projecting skin thermoreceptors (via TRPM8 channels in cold-sensing neurons).
- Amplified signals travel monosynaptically to CeA, heightening cold perception (chills) and motivating behaviors like huddling or seeking heat sources.
- Result: Behavioral fever complements autonomic responses, synergistically raising temperature to inhibit viruses/bacteria.
This bifurcation explains why chills feel emotionally aversive—CeA links to fear/discomfort circuits.
In Japan, where seasonal flu affects millions annually (over 10 million cases in 2025 per MHLW data), understanding this could refine antipyretic strategies.
Prof. Kazuhiro Nakamura: A Pioneer in Thermoregulation
With over 100 publications (h-index 50+ on Google Scholar), Nakamura has mapped fever's 'on-switch'—EP₃ POA neurons—and shivering circuits. His lab integrates optogenetics, pharmacogenetics, and in vivo imaging, training PhD students in cutting-edge techniques.
"We have identified part of the neural basis for emotional symptoms during infection," Nakamura noted. "Behavioral changes linked to fever are adaptive survival strategies." This perspective shifts chills from nuisance to evolutionary asset.
For aspiring researchers, Nakamura's career exemplifies Japan's academic path: MD-PhD at Nagoya, postdocs abroad, professorship via competitive grants. Explore tips for academic CVs or research positions in physiology.
Photo by Nemanja Milenkovic on Unsplash
Implications for Infectious Diseases and Beyond
This pathway offers therapeutic targets. Blocking LPB EP₃ could alleviate chills without blunting fever's benefits, ideal for vulnerable groups like elderly Japanese (aging population >29% over 65). In chronic conditions like rheumatoid arthritis, where PGE₂ drives inflammation, selective modulators might help.
Globally, fevers contribute to 5% of deaths in low-income settings (WHO), but adaptive in moderation. Japan's precision medicine push, via AMED funding, positions such research centrally.Nagoya press release
| Response Type | Brain Region | Effect |
|---|---|---|
| Autonomic | POA | Shivering, BAT heat |
| Behavioral | LPB → CeA | Chills, warmth-seeking |
Nagoya University: A Hub for Neuroscience in Japan
Nagoya University, founded 1871, ranks 6th nationally (THE 2026: 201-250 global) and #156 in neuroscience (US News). Home to 7 Nobel laureates, it excels in life sciences, with Graduate School of Medicine fostering interdisciplinary research. The Integrative Physiology department trains ~20 grad students yearly, emphasizing English publications and international collaborations.
In Japan's higher ed landscape, amid MEXT reforms boosting basic research (¥1.37 trillion FY2026), Nagoya leads. Students benefit from Moonshot programs funding bold neuroscience. Check Japan university jobs or RA opportunities.
Previous Nakamura Lab Contributions
Building on 2023 LPB thermosensory findings and 2022 POA 'master neurons' (Science Advances), this chills circuit completes the fever puzzle. Earlier: distinct cold/heat discomfort pathways (J Neurosci 2023), stress hyperthermia circuits.
- Identified rMR/DMH as sympathetic premotors for BAT/shivering.
- Linked limbic stress to tachycardia/hyperthermia, relevant for PTSD.
These lay groundwork for AI-modeling neural homeostasis, attracting postdocs.
Challenges and Future Outlook
Translating to humans requires fMRI/PET validation; CeA hyperactivity in depression suggests overlaps. Japan's aging society (life expectancy 84+) demands chill-relief for frail patients. Potential: EP₃ antagonists for 'comfort fever' management.
Horizons: Chronic inflammation (e.g., COVID long-haul), torpor studies. Nagoya plans human cohort studies, partnering globally.Nakamura Lab site
Careers in Japanese Neuroscience Research
This study exemplifies opportunities at top unis like Nagoya. PhDs in physiology command ¥5-7M starting salaries, rising with grants. International postdocs thrive via JSPS fellowships. Postdoc jobs, thrive as postdoc, or review profs at Rate My Professor.
Japan's research ecosystem, with 20% GDP on R&D, fuels such discoveries. Aspiring academics: master grantsmanship, publish in J Physiol-level journals.
In summary, Nagoya's chills revelation reframes infection responses as smart defenses, powered by elegant brain wiring. It bolsters Japan's neuroscience stature, inviting global collaboration. Stay informed via higher ed jobs, university jobs, career advice, and professor ratings.