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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 99/5/1782    most recent 00613.2005v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Xu, F. Articles by Lee, L.-Y. Search for Related Content PubMed PubMed Citation Articles by Xu, F. Articles by Lee, L.-Y.

Ovalbumin sensitization alters the ventilatory responses to chemical challenges in guinea pigs

¹Pathophysiology Program, Lovelace Respiratory Research Institute, Albuquerque, New Mexico; and ²Department of Physiology, University of Kentucky, Lexington, Kentucky

Submitted 24 May 2005 ; accepted in final form 11 July 2005

Patients with chronic bronchial asthma show a depressed ventilatory response to hypoxia (DVH), but the underlying mechanism remains unclear. We tested whether DVH existed in ovalbumin (Ova)-treated guinea pigs, an established animal model of asthma. Twelve guinea pigs were exposed to Ova (1% in saline) or saline aerosol (control) for 5 min, 5 days/wk, for 2 wk. After completing aerosol exposure, the animals were anesthetized and exposed to systemic hypoxia. Ova treatment had no effects on animal body weight, baseline cardiorespiratory variables, or arterial blood O₂ and CO₂ tensions, but it attenuated the ventilatory response to hypoxia (10 breaths of pure N₂) by 65% (P < 0.05). When the animals were subjected to intracarotid injections of sodium cyanide (20 µg) and doxapram (2 mg) to selectively stimulate carotid chemoreceptors, the ventilatory responses were reduced by 50% (P < 0.05) and 74% (P < 0.05), respectively. In contrast, Ova exposure failed to affect the ventilatory response to CO₂ (7% CO₂-21% O₂-balance N₂ for 5 min; P > 0.05). Furthermore, the apneic response evoked by stimulating bronchopulmonary C fibers (PCFs) with right atrial injection of capsaicin (5 µg) was markedly increased in the Ova-sensitized group (5.02 ± 1.56 s), compared with the control group (1.82 ± 0.45 s; P < 0.05). These results suggest that Ova sensitization induces a DVH in guinea pigs, which probably results from an attenuation of the carotid chemoreceptor-mediated ventilatory excitation and an enhancement of the PCF-mediated ventilatory inhibition.

carotid body; bronchopulmonary C fibers; hypoxia; capsaicin; inflammation

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