Is our sensitivity to pain influenced by signals coming from our blood vessels? This could explain why when we raise the arm on which a capsaicin patch is applied, the pain becomes much worse, a phenomenon we describe and probe in our latest paper doi.org/10.1002/ejp.... A 🧵 - ThreadSky

acourtin.bsky.social • 119 days ago

Is our sensitivity to pain influenced by signals coming from our blood vessels? This could explain why when we raise the arm on which a capsaicin patch is applied, the pain becomes much worse, a phenomenon we describe and probe in our latest paper https://doi.org/10.1002/ejp.4742
A 🧵

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acourtin.bsky.social•119 days ago

We stumbled upon this phenomenon while piloting a different experiment. Sabien van Neerven was at her desk, wearing a capsaicin patch on her forearm. When she casually placed her hands behind her head, the pain -which had faded- suddenly flared up, becoming excruciating.

acourtin.bsky.social•119 days ago

Intrigued, we set out to replicate this phenomenon and investigate its mechanism. To do so, we repeatedly probed sensations evoked by a capsaicin and a vehicle patch, in resting position and during arm raising, as well as pinprick secondary hyperalgesia (central sensitization).

acourtin.bsky.social•119 days ago

Our results show that the arm raising effect is very robust and that it is driven by the position of the arm relative to the ground (gravity) rather than to the body (i.e., the effect is the same when the arm is vertical, whether a person is sitting or lying down).

acourtin.bsky.social•119 days ago

Contrary to our hypothesis, this effect did not seem caused by the heterosynaptic long-term potentiation like mechanisms underlying pinprick secondary hyperalgesia (central sensitization), as evidenced by the lack of temporal correlation between the decays of both phenomena.

acourtin.bsky.social•119 days ago

In the paper, we speculate about possible mechanisms, which include crosstalk between the vascular and the nociceptive systems. Overall, we are left with more questions than answers but we think we have laid the groundwork for future investigations of this intriguing phenomenon!

acourtin.bsky.social•119 days ago

Thank you to all the people involved in this project and the funders who made it possible to pursue it!
And thank you @micahgallen.com for the thread writing advice!

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