Effects of aerosolized histamine and carbachol in the conscious horse.
Abstract: Pulmonary function tests were performed in seven conscious, standing horses. Changes in pulmonary mechanics and ventilation volumes were measured after inhalation challenge with saline (baseline), histamine (1% w/v solution for 5 min) and carbachol (0.5% w/v solution for 3 min). Comparisons between baseline and posthistamine values revealed a significant (P less than 0.05) increase in nonelastic work of breathing (Wb), maximum change in transpulmonary pressure (max delta Ppl), and pulmonary resistance (RL), while dynamic compliance (Cdyn) decreased (P less than 0.05). Tripelennamine completely abolished these histamine induced changes suggesting the involvement of H1 receptors. A nonsignificant increase occurred in functional residual capacity. However, the amount of nitrogen retained in the lung at the end of a nitrogen washout test was significantly (P less than 0.05) greater after histamine when compared to baseline values. The effect of carbachol was qualitatively similar to that of histamine, Wb and max delta Ppl increased while Cdyn decreased (P less than 0.05). The increase in lower RL reached statistical significance (P less than 0.05) only at the beginning of expiration (/ 25% VT). The present investigation demonstrates that the physiological measurements of lung function could be carried out in conscious, unsedated horses and that the pulmonary function test methods could be used as a tool for study of drug induced changes in pulmonary mechanics.
Publication Date: 1985-04-01 PubMed ID: 4016587PubMed Central: PMC1236152
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study investigates the changes in lung function and mechanics in conscious horses, following the inhalation of histamine, carbachol and saline. The experiments highlighted significant increases in nonelastic work of breathing, transpulmonary pressure, and pulmonary resistance, as well as a decrease in dynamic compliance after exposure to histamine and carbachol, indicating these substances can notably impact equine respiratory physiology.
Study Design and Methodology
- The study was conducted on seven conscious standing horses, which were not sedated during the tests. This step was crucial in ensuring the normality of the respiratory responses.
- Pulmonary function tests were carried out to gauge the changes in pulmonary mechanics and ventilation volumes. The horses were exposed to three aerosolized substances in separate trials: saline (as a baseline), histamine, and carbachol. The histamine solution was applied for five minutes, and carbachol was applied for three minutes.
- Post-inhalation, various parameters like work of breathing, transpulmonary pressure, pulmonary resistance, and dynamic compliance were measured and compared with the baseline values established using saline.
Findings and Conclusions
- Exposure to histamine led to a significant increase in the nonelastic work of breathing, change in transpulmonary pressure, and pulmonary resistance, while a decrease was noticed in dynamic compliance. All these changes point towards an increased resistance and efforts to breathe, impacting the lung function negatively.
- The same effects were observed with carbachol, further substantiating the impact of these substances on horse pulmonary function.
- The administration of Tripelennamine, a histamine H1 receptor antagonist, effectively eliminated the changes induced by histamine, indicating the involvement of H1 receptors in these physiological modifications.
- The results also revealed a non-significant increase in functional residual capacity. However, after the histamine exposure, the amount of nitrogen retained in the lungs significantly increased in comparison to the baseline. This suggests a potential constriction in the airways, limiting the expulsion of nitrogen during the washout test.
- Through these investigations, it was demonstrated that these methods could be effectively utilized for studying drug-induced changes in pulmonary dynamics in conscious and unsedated horses. The findings have far-reaching implications in understanding equine respiratory physiology and related disease conditions.
Cite This Article
APA
Mirbahar KB, McDonell WN, Bignell W, Eyre P.
(1985).
Effects of aerosolized histamine and carbachol in the conscious horse.
Can J Comp Med, 49(2), 211-218.
Publication
Researcher Affiliations
MeSH Terms
- Aerosols
- Analysis of Variance
- Animals
- Carbachol / pharmacology
- Female
- Histamine / pharmacology
- Horses / physiology
- Lung / drug effects
- Lung / physiology
- Male
- Respiratory Function Tests / methods
- Respiratory Function Tests / veterinary
- Tripelennamine / pharmacology
References
This article includes 18 references
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Citations
This article has been cited 3 times.- Léguillette R, Tohver T, Bond SL, Nicol JA, McDonald KJ. Effect of Dexamethasone and Fluticasone on Airway Hyperresponsiveness in Horses With Inflammatory Airway Disease. J Vet Intern Med 2017 Jul;31(4):1193-1201.
- Whiting TL, Tesarowski DB. On the meaning and utility of diagnostic terms: Special reference to bronchopulmonary abnormalities in the horse. Can Vet J 1988 Oct;29(10):787-9.
- Doucet MY, Vrins AA, Ford-Hutchinson AW. Histamine inhalation challenge in normal horses and in horses with small airway disease. Can J Vet Res 1991 Jul;55(3):285-93.
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