Nerve growth factor expression after plantar incision in the rat.
BACKGROUND
Postoperative pain control remains a significant problem. Advances will proceed if we can further reveal the underlying mechanisms of incisional pain and its mediators. Previous studies have demonstrated that nerve growth factor (NGF) is released in incised tissue and contributes to hyperalgesia in incisional pain. The purpose of this study is to examine the expression of NGF in skin after planter incision.


METHODS
Adult Sprague-Dawley rats underwent incision at the plantar aspect of hind paw. The NGF messenger RNA (mRNA) was measured at various times after incision by polymerase chain reaction. NGF protein expression was detected by Western blot and immunohistochemistry in incisions.


RESULTS
NGF mRNA increased from 2 to 4 h after incision and was the same as control by postoperative day 1. A large-molecular-weight form of NGF, approximately 75 kd, was found in normal skin. The large-molecular-weight NGF protein increased 4 h after incision and returned to baseline on postoperative day 7. The skin immediately adjacent to the incision had the greatest NGF expression. Immunohistochemical staining for NGF was present adjacent to the incision and localized in Schwann cells and axons.


CONCLUSIONS
NGF mRNA is increased and a large-molecular-weight form of NGF protein is expressed in the region adjacent to the incision. NGF immunoreactivity is present in nerve bundles; both Schwann cells and axons are labeled. Immunoreactive NGF in axons is likely taken up into cut axons. This study suggests some common mechanisms for neuropathic and incisional pain.
Wu
Chaoran
C
Department of Anesthesia, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA. chaoran-wu@uiowa.edu
Boustany
Leila
L
Liang
Hong
H
Brennan
Timothy J
TJ
D015100:3,3'-Diaminobenzidine; D000199:Actins / Q000378:metabolism; D000818:Animals; D001369:Axons / Q000378:metabolism; D015153:Blotting, Western; D005455:Fluorescent Antibody Technique; D018409:Foot Injuries / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000096:biosynthesis; D007150:Immunohistochemistry; D008297:Male; D020932:Nerve Growth Factor / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D009418:S100 Proteins / Q000378:metabolism; D012583:Schwann Cells / Q000378:metabolism; D014018:Tissue Distribution; D043222:Ubiquitin Thiolesterase / Q000378:metabolism
D000199:Actins; D012333:RNA, Messenger; D009418:S100 Proteins; D015100:3,3'-Diaminobenzidine; D020932:Nerve Growth Factor; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; C489034:UCHL1 protein, rat; D043222:Ubiquitin Thiolesterase