Background & Aims

It is well known that atmospheric pressure change can be one of the meteorological factors that trigger or exacerbate pain in humans. We previously reported that neuropathic pain-related behavior in rats is aggravated by lowering barometric pressure, and that this effect is blocked by sympathectomy. These results suggest that mechanisms that increase sympathetic activity may parallel those that contribute to meteoropathy generation.
However, it remains unknown whether changes in barometric pressure activate Hypothamic-Pituitry-Adrenal (HPA) axis. To address this issue, we used corticosterone measurement as a marker for HPA axis activation in mice.

Methods

We used forty-eight female C57BL/6J mice (10 weeks-old) in this study. Chronic constriction injury of the sciatic nerve (CCI surgery) was performed in mice to induce neuropathic pain. Mechanical response was evaluated by using von Frey hair test. All mice showed mechanical hyperalgesia (increase in number of paw-withdrawal) three weeks after CCI surgery, and were used in the further experiments.
Experiment 1: Mice were placed in a climatic chamber, and the barometric pressure was lowered by 20 hPa from atmospheric pressure at the beginning of the experiment (LP stimulation): single LP or three-times consecutive LPs (3LPs). Behavioral tests were performed before and after LP stimulation. A group of animals was placed in the chamber without pressure changes and served as the normal pressure group.
Experiment 2: Plasma sample was collected from CCI and intact mice exposed to 3LPs. Plasma corticosterone level was measured by ELISA.

Results

Experiment 1: After 3LPs protocol, number of paw-withdrawal significantly increased in CCI mice. On the other hand, groups of CCI animals placed in the chamber without barometric pressure change did not show any changes in number of paw-withdrawal. After single LP protocol, no significant differences in number of paw-withdrawal of CCI animals.
Experiment 2: In CCI mice, corticosterone level in plasma significantly increased after 3LPs protocol. On the other hand, in intact mice, corticosterone level in plasma was not increased after 3LPs protocol.

Conclusions

The present study showed that three-times lowering barometric pressure increased sensitivity to mechanical stimulation in mice with neuropathic pain. Our data suggests that a fluctuation of barometric pressure is one of important meteorological factors increasing pain in mice. Furthermore, the fact that the elevation of plasma corticosterone levels was observed only in mice with neuropathic pain. This result suggests that chronic pain conditions is an essential factor of hypersensitivity to barometric pressure change, and HPA axis activation may have an important relationship to LP-induced pain in mice.

References

Horvath G, Nagy K, Tuboly G, Nagy E. Pain and weather associations – Action mechanisms; personalized profiling. Brain Research Bulletin. 2023;200:110696. doi:10.1016/j.brainresbull.2023.110696
Sato J, Morimae H, Seino Y, Kobayashi T, Suzuki N, Mizumura K. Lowering barometric pressure aggravates mechanical allodynia and hyperalgesia in a rat model of neuropathic pain. Neuroscience Letters. 1999;266(1):21-24.
Sato J, Takanari K, Omura S, Mizumura K. Effects of lowering barometric pressure on guarding behavior, heart rate and blood pressure in a rat model of neuropathic pain. Neuroscience letters. 2001;299(1-2):17-20.
Sato J, Inagaki H, Kusui M, Yokosuka M, Ushida T. Lowering barometric pressure induces neuronal activation in the superior vestibular nucleus in mice. PLoS One. 2019;14(1):e0211297.

Presenting Author

Yuki Terajima

Poster Authors

Yuki Terajima

MD

Aichi Medical University Medical Center

Lead Author

Jun Sato

PhD

Department of Physical Therapy, College of Life and Health Sciences, Chubu University

Lead Author

Takahiro Ushida

Multidisciplinary Pain Center, Aichi Medical University

Lead Author

Hideaki Inagaki

PhD

Department of Pain Medicine, Aichi Medical University

Lead Author

Topics

  • Mechanisms: Biological-Systems (Physiology/Anatomy)