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This Article Full Text Full Text (PDF) All Versions of this Article: 91/6/1025    most recent expphysiol.2006.034868v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal 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 Google Scholar Google Scholar Articles by Braga, V. A. Articles by Machado, B. H. Search for Related Content PubMed PubMed Citation Articles by Braga, V. A. Articles by Machado, B. H.

Department of ¹ Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil

In the present study, we tested the hypothesis that chronic intermittent hypoxia (CIH) produces changes in the autonomic and respiratory responses to acute peripheral chemoreflex activation. To attain this goal, 3-week-old rats were exposed to 10 days of CIH (6% O₂ for 40 s at 9 min intervals; 8 h day^–1). They were then used to obtain a working heart–brainstem preparation and, using this unanaesthetized experimental preparation, the chemoreflex was activated with potassium cyanide (0.05%, injected via the perfusion system), and the thoracic sympathetic nerve activity (tSNA), heart rate and phrenic nerve discharge (PND) were recorded. Rats subjected to CIH (n = 12), when compared with control animals (n = 12), presented the following significant changes in response to chemoreflex activation: (a) an increase in tSNA (78 ± 4 versus 48 ± 3%); (b) a long-lasting increase in the frequency of the PND at 20 (0.52 ± 0.03 versus 0.36 ± 0.03 Hz) and 30 s (0.40 ± 0.02 versus 0.31 ± 0.02 Hz) after the stimulus; and (c) a greater bradycardic response (–218 ± 20 versus –163 ± 16 beats min^–1). These results indicate that the autonomic and respiratory responses to chemoreflex activation in juvenile rats previously submitted to CIH are greatly increased.

(Received 22 June 2006; accepted after revision 30 August 2006; first published online 7 September 2006)
Corresponding author B. H. Machado: Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil.  Email: bhmachad{at}fmrp.usp.br

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