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Effects of sciatic nerve injuries on δ ‐opioid receptor and substance P immunoreactivities in the superficial dorsal horn of the rat
Author(s) -
Robertson Brita,
Schulte Gunnar,
Elde Robert,
Grant Gunnar
Publication year - 1999
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1053/eujp.1998.0104
Subject(s) - substance p , sciatic nerve , opioid , medicine , opioid receptor , neuropathic pain , crush injury , anesthesia , peripheral nerve injury , receptor , ligation , endocrinology , surgery , neuropeptide
The aim of the present study was to examine the effects of transection combined with tight ligation, and crush of the sciatic nerve on δ ‐opioid receptor and substance P immunoreactivities in the superficial spinal dorsal horn at different time points after injury. Both the δ ‐opioid receptor and substance P are primarily localised to primary afferent fibres and terminals. Seven days following transection and ligation, a slight decrease in both δ ‐opioid receptor and substance P levels was seen in laminae I and II. The maximal reduction appeared to take place around 4 weeks. Restoration of immunoreactivity was observed by 32 weeks, and by 1 year the levels were almost back to normal. Regarding crush injury, the reduction in both δ ‐opioid receptor and substance P immunoreactivities were less pronounced and recovery was faster than after transection injury. Already by 16 weeks, the levels were almost back to normal. These results show that peripheral nerve injuries dramatically reduce the levels of δ ‐opioid receptor and substance P immunoreactivities in the superficial dorsal horn after short survivals and demonstrate recovery after long survivals. Whether the marked reduction of δ ‐opioid receptors in the dorsal horn is involved in the decreased ability of opioid analgesics to alleviate neuropathic pain remains to be studied.