Dissociation between post-surgical pain behaviors and spinal Fos-like immunoreactivity in the rat.

Abstract

Previous studies have demonstrated that Fos-like immunoreactivity is increased in spinal dorsal horn neurons in several pain models, and have suggested that Fos-like immunoreactivity could be used as a marker of neurons activated by painful stimulation. In the present study, we evaluated nociceptive behaviors and spinal Fos-like immunoreactivity in a rat skin incision model of post-operative pain. In this model, evoked and non-evoked pain behaviors were observed at least for 2 days after paw surgery, an increased number of Fos-like immunoreactive neurons was observed in the spinal dorsal horn at lumbar levels 4-5 two-hour post-surgery. The number of Fos-like immunoreactive neurons was significantly greater in animals with skin-muscle incision compared to animals with skin-alone incision. Interestingly, spinal Fos-like immunoreactivity was quickly normalized in rats with paw surgery at later time points (8 and 24 h post-surgery), whereas nociceptive behaviors were still observed. Furthermore, at 24 h post-surgery, spinal Fos-like immunoreactivity induced by thermal stimulation (42, 44, 46, 48, 52 degrees C for 15 s) was not significantly different between sham animals and animals with surgery. In both groups, an increase in spinal Fos-like immunoreactive neurons was observed with increasing temperatures, with similar laminar distribution. Finally, systemic morphine reduced post-operative pain and Fos-like immunoreactivity in a naloxone reversible manner, with greater potency and efficacy on behavioral endpoints than on Fos-like immunoreactivity. These results demonstrate a different profile of nociceptive behaviors and spinal Fos-like immunoreactivity in the rat skin incision model, suggesting a limited potential of spinal Fos-like immunoreactivity to study post-surgical pain and its pharmacology.

• Authors: Chang Z Zhu, Arthur L Nikkel, Brenda Martino, Robert S Bitner, Michael W Decker, Prisca Honore
• Journal: European journal of pharmacology (Eur J Pharmacol) Vol. 531 Issue 1-3 Pg. 108-17 (Feb 15 2006) ISSN: 0014-2999 [Print] Netherlands
• PMID: 16438960 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Analgesics, Opioid
• Narcotic Antagonists
• Proto-Oncogene Proteins c-fos
• Naloxone
• Morphine

Topics

• Analgesics, Opioid (pharmacology)
• Animals
• Dermatologic Surgical Procedures
• Dose-Response Relationship, Drug
• Hindlimb (surgery)
• Immunohistochemistry
• Male
• Morphine (pharmacology)
• Muscles (surgery)
• Naloxone (pharmacology)
• Narcotic Antagonists (pharmacology)
• Pain, Postoperative (physiopathology, prevention & control)
• Posterior Horn Cells (chemistry, drug effects)
• Proto-Oncogene Proteins c-fos (analysis)
• Rats
• Rats, Sprague-Dawley
• Spinal Cord (chemistry, drug effects)
• Temperature
• Time Factors