title: Neurokinin receptors in recurrent airway obstruction: a comparative study of affected and unaffected horses.
abstract: The purpose of the study was to compare in vitro airway responses to neurokinin A & B (NKA and NKB) and expression of NK-2 receptors in airways of horses affected and unaffected with recurrent airway obstruction (RAO). Neurokinin-A, an inflammatory mediator belonging to the tachykinin family of neuropeptides, causes bronchoconstriction by binding to NK-2 receptors. Neurokinin-B is a lesser-known neuropeptide that acts on NK-3 receptors. Horses were placed into RAO-affected and RAO-unaffected groups based on their history, clinical scoring, and pulmonary function testing. Lung tissue from each lobe was collected for immunohistochemical staining for NK-2 receptors. Cumulative concentration-response relationships were determined on bronchial rings (4-mm wide) collected and prepared from the right diaphragmatic lung lobe to graded concentrations (half log molar concentrations 10(-7)M to 10(-4)M) of NKA and NKB. The results showed that NKA caused significantly greater contraction than NKB in both groups. In RAO-affected horses, both agents produced significantly greater bronchial contractions than those in the RAO-unaffected horses. Immunohistochemical staining showed that the overall NK-2 receptor distribution was significantly increased in bronchial epithelium and smooth muscles of bronchi and pulmonary vessels of RAO-affected than RAO-unaffected horses. The findings indicate that NK-2 receptors are up-regulated in RAO, suggesting that NK-2 receptor antagonists may have some therapeutic value in controlling the progression of airway hyperreactivity in horses affected with RAO.
authors.affiliation: Equine Health Studies Program, Departments of Veterinary Clinical Science and Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana 70803, USA. cvenugopal@vetmed.lsu.edu
authors.forename: Changaram S
authors.initials: CS
authors.lastname: Venugopal
authors.forename: Earnestine P
authors.initials: EP
authors.lastname: Holmes
authors.forename: Sumanth
authors.initials: S
authors.lastname: Polikepahad
authors.forename: Susan
authors.initials: S
authors.lastname: Laborde
authors.forename: Michael
authors.initials: M
authors.lastname: Kearney
authors.forename: Rustin M
authors.initials: RM
authors.lastname: Moore