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Effects of peripheral inflammation on activation of ERK in the rostral ventromedial medulla

Hiroki Imbe1, Keiichiro Okamoto, Tomoharu Okamura

  • 1Department of Anatomy and Neurobiology, Wakayama Medical University, Kimiidera 811-1, Wakayama City, 641-8509, Japan. imika@js9.so-net.ne.jp

Brain Research
|November 18, 2005
PubMed

Insights

Peripheral inflammation activates extracellular signal-regulated kinase (ERK) in the rostral ventromedial medulla (RVM). This activation, particularly in serotonergic neurons, suggests a role in the descending pain modulatory system

Area of Science:

  • Neuroscience
  • Pain Research
  • Cellular Signaling

Background:

  • Peripheral inflammation triggers complex neural responses.
  • The descending pain modulatory system regulates pain perception.
  • Extracellular signal-regulated kinase (ERK) signaling is implicated in neural plasticity.

Purpose of the Study:

  • To investigate the activation of ERK in the RVM following peripheral inflammation.
  • To elucidate the role of ERK in the RVM within the descending pain modulatory system.
  • To determine the involvement of serotonergic neurons in inflammation-induced RVM ERK activation.

Main Methods:

  • Complete Freund's adjuvant (CFA) was injected into the rat hindpaw to induce inflammation.
  • Immunohistochemistry was used to detect phospho-extracellular signal-regulated kinase (p-ERK)-immunoreactive neurons in the RVM.
  • Co-localization studies identified p-ERK positive neurons within the serotonergic population.

Main Results:

  • CFA injection significantly increased the number of p-ERK-IR neurons in the RVM compared to controls.
  • ERK activation in the RVM peaked at 7 hours and lasted for 24 hours post-CFA injection.
  • Approximately 60% of inflammation-induced p-ERK-IR neurons in the RVM were serotonergic, a sevenfold increase compared to controls.

Conclusions:

  • Inflammation induces significant ERK activation in the RVM, particularly in serotonergic neurons.
  • This inflammation-induced ERK activation in the RVM is likely involved in the plasticity of the descending pain modulatory system.
  • Findings highlight a potential mechanism for altered pain modulation during inflammatory states.

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