Sympathoexcitatory response to peripheral chemoreflex activation is enhanced in juvenile rats exposed to chronic intermittent hypoxia

Exp Physiol. 2006 Nov;91(6):1025-31. doi: 10.1113/expphysiol.2006.034868. Epub 2006 Sep 7.

Abstract

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% O(2) 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Autonomic Nervous System / physiology
  • Body Weight / physiology
  • Bradycardia / physiopathology
  • Chemoreceptor Cells / drug effects
  • Chemoreceptor Cells / physiology*
  • Enzyme Inhibitors / pharmacology
  • Heart Rate / physiology
  • Hypoxia / physiopathology*
  • Peripheral Nervous System / physiology*
  • Phrenic Nerve / physiology
  • Potassium Cyanide / pharmacology
  • Rats
  • Respiratory System / drug effects
  • Sympathetic Nervous System / physiology*

Substances

  • Enzyme Inhibitors
  • Potassium Cyanide