In vitro responses of distal airways in horses with recurrent airway obstruction.
Abstract: Distal airway segments (ID, 3 to 4 mm; length, 5 mm) from 2 groups of horses were isolated and suspended in tissue baths filled with Krebs solution, aerated with 5% CO2 in oxygen and maintained at 37 degrees C. Responses to exogenous acetylcholine, isoproterenol, or electrical field stimulation were compared. Control horses (n = 30) had no history of recurrent airway obstruction, whereas principal horses (n = 15) had recurrent airway obstruction and were studied during an acute episode of airway obstruction. Although the distal airways contracted in response to the cumulative half-logarithmic addition of acetylcholine (10(-10) M to 10(-3) M) in both groups, bronchi obtained from principals were less sensitive to acetylcholine than were bronchi obtained from controls. Tetdrodotoxin-sensitive electrical field stimulation-induced contractions were observed in both groups of airways, but the tension achieved in principal bronchi was less than in controls. All electrical field stimulation-induced contractions were abolished by atropine, indicating that the only excitatory innervation of equine distal airway is through the parasympathetic system. To examine the effect of isoproterenol and determine inhibitory innervation, bronchi were precontracted with histamine. Electrical field stimulation did not cause relaxation of precontracted bronchi in either group, thus indicating that distal airways lack inhibitory innervation. Isoproterenol caused similar, dose-dependent relaxation in both groups.
Publication Date: 1991-07-01 PubMed ID: 1892280
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- Journal Article
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This study investigates the in vitro responses of distal airways to different stimulants in horses with recurrent airway obstruction (RAO), a common respiratory disease, compared to a control group of horses without RAO. The study implies that the airways of horses affected by RAO react differently to certain stimulants and lack inhibitory innervation.
Research Procedure
- The study involved two groups of horses; 30 that were free from recurrent airway obstruction (RAO) and acted as controls, and 15 that had RAO and were undergoing an acute episode of airway obstruction.
- Distal airway segments were isolated from each horse and subjected to a tissue bath, maintained at 37 degrees Celsius and aerated with 5% carbon dioxide in oxygen.
- The samples then underwent testing for responses to acetylcholine, isoproterenol, and electrical field stimulation.
Findings
- When all the airway segments were subjected to acetylcholine, they contracted. However, samples from horses with RAO contracted less in response to acetylcholine when compared to the control group. This suggests that the bronchi from horses with RAO were less sensitive to acetylcholine.
- Both groups displayed contractions in response to tetrodotoxin-sensitive electrical field stimulation. However, the bronchi from horses with RAO achieved less tension compared to those from the control group.
- All contractions induced by electric field stimulation stopped when treated with atropine. This demonstrates that the parasympathetic system is the only excitatory innervation for the equine distal airway.
Additional Tests
- The researchers also examined the effects of isoproterenol and searched for inhibitory innervation. For these tests, bronchi were pre-contracted with histamine and then subjected to electrical field stimulation.
- Neither groups’ pre-contracted bronchi relaxed with the electrical field stimulation. This suggests that the distal airways lack inhibitory innervation.
- However, isoproterenol caused a similar, dose-dependent relaxation in both groups of bronchi.
Implications of the Study
- The study indicates that horses suffering from RAO have different responses and sensitivities to various stimulants compared to horses without the condition. This could potentially have implications for the treatment and management of RAO.
- The lack of inhibitory innervation in the distal airways may also influence the development and treatment of airway diseases.
- The findings could be used to direct further research into more effective treatments for airway diseases.
Cite This Article
APA
LeBlanc PH, Broadstone RV, Derksen FJ, Robinson NE.
(1991).
In vitro responses of distal airways in horses with recurrent airway obstruction.
Am J Vet Res, 52(7), 999-1003.
Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, Michigan State University, East Lansing 48824.
MeSH Terms
- Acetylcholine / pharmacology
- Airway Obstruction / physiopathology
- Airway Obstruction / veterinary
- Animals
- Bronchi / drug effects
- Bronchi / innervation
- Bronchi / physiopathology
- Culture Techniques
- Dose-Response Relationship, Drug
- Electric Stimulation
- Horse Diseases / physiopathology
- Horses
- Isoproterenol / pharmacology
- Recurrence
Grant Funding
- HL 01742 / NHLBI NIH HHS
- HL 27619 / NHLBI NIH HHS
Citations
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