Effects of metergoline or pisotifen on capsaicin-induced cough in normal volunteers treated with buspirone (original) (raw)

1997, Current Therapeutic Research

Serotonin (5-hydroxytryptamine [5-HT]) has been shown to act as a modulator of the cough reflex in some species; however, the subtype of the 5-HT receptor influencing the cough reflex remains to be clarified. In this study, we compared the influence of prolonged treatment with buspirone (a 5-HT~A dualist), alone or combined with metergoline (a 5-HT 1 antagonist), pisotifen (a 5-HT 2 antagonist), or placebo, on capsaicin-induced cough. Fourteen normal volunteers with no history of respiratory infection within the preceding 6 weeks were involved in the study. For the construction of capsaicin cough dose-response curves the subjects took single breaths at 30-second intervals of either sodium chloride or a range of doses of capsaicin (0.4-50 nmol) in random order from a nebulizer controlled by a breath-activated dosimeter. The number of coughs occurring in the 30 seconds following each inhalation was noted and the results were expressed as the total cough count, the concentration of capsaicin causing two coughs (D2), and the concentration causing five or more coughs (D5). There were no statistically significant differences in D2, D5, or the total cough count with any of the treatment regimens when compared with the baseline capsaicin response obtained on the first study day. This study, therefore, shows that bnspirone does not significantly influence capsaicin-induced cough in humans, either alone or in the presence of various 5-HT antagonists. However, the bnspironeJpisotifen combination tended to be more cough-suppressing.

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