The Journal of veterinary medical science
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Cardiovascular reflex mechanisms by topical laryngeal instillation of capsaicin (CAPS) or distilled water were evaluated in anesthetized chronic tracheostomized dogs. Both CAPS (10 micrograms/ml) and water instillation into the isolated upper airway caused a significant decrease in heart rate (P < 0.05) and a significant increase in blood pressure (P < 0.05) from the values before instillation under both spontaneous and controlled ventilation. ⋯ All the reflex responses to CAPS and water were eliminated by topical anesthesia with lidocaine. It was concluded that the laryngeal cardiovascular reflex responses were mediated by the afferents such as the laryngeal CAPS-sensitive presumably C-fiber endings or water-responsive receptors and by both the parasympathetic and sympathetic nervous systems as efferents.