Evaluation of opioid receptors in synovial membranes of horses.

TitleEvaluation of opioid receptors in synovial membranes of horses.
Publication TypeJournal Article
Year of Publication2001
AuthorsSheehy JG, Hellyer PW, Sammonds GE, Mama KR, Powers BE, Hendrickson DA, Magnusson KR
JournalAmerican journal of veterinary research
Volume62
Issue9
Pagination1408-12
Date Published2001 Sep
ISSN0002-9645
KeywordsAnimals, Arthroscopy, Horse Diseases, Horses, Immunohistochemistry, Inflammation, Naloxone, Narcotic Antagonists, Receptors, Opioid, mu, Stifle, Synovial Membrane
Abstract

OBJECTIVE: To evaluate mu-opioid receptors in synovial membranes of horses and determine whether these receptors are up-regulated in nerve endings during inflammation.

SAMPLE POPULATION: Synovial tissue obtained from 39 client-owned horses during arthroscopy and 14 research horses during necropsy; brain and synovial tissues were obtained during necropsy from 1 horse, and control tissues were obtained from a mouse.

PROCEDURE: Horses were classified into 7 groups on the basis of histologically determined degree of inflammation. Binding of primary rabbit antibody developed against mu-opioid receptors in equine synovial tissue was studied, using western blot analysis. Synovial membranes were tested for mu-opioid receptors by immunohistochemical staining, using a diaminobenzidine-cobalt chloride chromogen. Homogenates of synovial membranes were evaluated by use of radioligand binding.

RESULTS: Examination of western blots of equine thalamus revealed that rabbit antibody developed against mu-opioid receptors yielded a band (molecular weight, 55 kd) that corresponded with that of other opioid receptors. Use of immunohistochemical staining of synovial tissue revealed considerable staining in the proliferative lining layer and in regions surrounding vascular structures. Specific radioligand binding of tissue homogenates was found in all groups. We did not detect significant differences in binding between horses with inflammation and horses without inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE: Results of immunohistochemical analysis and radioligand binding of tissue homogenates suggest that there are opioid receptors in synovial membranes of horses. Our results support the practice of intra-articular administration of opioids to relieve pain after arthroscopic surgery in horses.

Alternate JournalAm. J. Vet. Res.