Highlights
- •A novel rat model of acute postoperative pain has been developed.
- •It represents the first animal model of acute pain following inguinal hernia repair.
- •The model is characterized by deficits in locomotor activity, reversible by analgesics.
- •Pain-related phenotype is driven primarily by activation of deep somatic or visceral nociceptors.
- •The model is associated with increased c-Fos expression in the dorsal horn.
Abstract
Acute postoperative pain remains a significant health care issue. Development of anatomically
relevant animal models of postoperative pain, with improved predictive validity, would
advance understanding of postoperative pain mechanisms and improve treatment outcomes.
This study aimed to develop, characterize, and validate a rat model of acute postoperative
pain associated with inguinal hernia repair based on the Lichtenstein inguinal hernia
repair procedure (without hernia induction). We hypothesized that the surgery would
result in reduced spontaneous locomotor activity, which would represent a pain-related
phenotype. Postsurgical characterization involved extensive monitoring of home cage
and open field locomotor activity, as well as mechanical hypersensitivity and assessment
of c-Fos expression in the dorsal horn of the spinal cord. In pharmacologic validation
studies, rats received morphine, carprofen, or paracetamol 1 hour before, and/or immediately
after, surgery. Rats that underwent hernia repair surgery exhibited significantly
lower horizontal and vertical activities in the home cage and open field in the early
postsurgical period, compared with sham rats or rats that underwent skin incision
only. Morphine, carprofen, and paracetamol attenuated the surgery-induced reductions
in locomotor activity, to varying degrees. Surgery was associated with significantly
increased c-Fos expression in the ipsilateral dorsal horn of the spinal cord, an effect
attenuated by carprofen treatment. These results support the development and characterization
of a novel, anatomically relevant animal model of acute postoperative pain that may
facilitate development of improved treatment regimens.
Perspective
Acute pain following inguinal hernia repair can be difficult to treat. Here we report,
for the first time, the development of a novel, anatomically relevant rat model to
facilitate improved understanding and treatment of acute postoperative pain following
inguinal hernia repair.
Key words
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Article info
Publication history
Published online: January 29, 2015
Accepted:
January 13,
2015
Received in revised form:
January 7,
2015
Received:
November 30,
2014
Footnotes
The authors have no conflicts of interest to declare. This project was funded by a grant from the Irish Industrial Development Agency in partnership with Covidien. The Irish Industrial Development Agency played no part in study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the article for publication. Coauthors O.M., C.O.M., and D.C.B. at Covidien did contribute to these elements.
Supplementary data accompanying this article are available online at www.jpain.org and www.sciencedirect.com.
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© 2015 American Pain Society. Published by Elsevier Inc. All rights reserved.
