ScienceDaily (June 17, 2008) — The increased beating of the heart that one experiences when in a stressful situation is just one part of the body's response to stress, something often known as the "fight-or-flight response".  Another component of the fight-or-flight response is the suppression of pain, also known as stress-induced analgesia (SIA).

Some of the nerves and nerve-produced peptides that are responsible for SIA have been identified, but much remains to be discovered. In a new study, a team of researchers in California, from AfaSci, Inc., Burlingame, and SRI International, Menlo Park, has revealed that nerves producing the peptide N/ORQ and nerves producing the peptide Hcrt are key in regulating SIA in mice.

The research team, which was led by Xinmin Xie and Thomas Kilduff, showed that in the brain of normal mice, Hcrt-producing nerve cells (Hcrt neurons) and N/ORQ-producing nerve cells interacted. N/ORQ affected the electrical current across Hcrt neurons and the release of neurotransmitters by these cells.

Furthermore, administration of N/ORQ blocked SIA in normal mice, but this was overcome by administration of Hcrt at the same time. The authors therefore conclude that N/ORQ likely influences a variety of Hcrt-mediated processes, in addition to SIA, and suggest that these pathways might contribute to medical conditions caused by excessive stress, such as anxiety and post-traumatic stress disorder.

Journal reference:

1. Xinmin (Simon) Xie, Thomas Kilduff et al. Hypocretin/orexin and nociceptin/orphanin FQ coordinately regulate analgesia in a mouse model of stress-induced analgesia. Journal of Clinical Investigation, June 12, 2008

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