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Postnatal intermittent hypoxia alters baroreflex function in adult rats
Galia K Soukhova-O'Hare1, Zixi Jack Cheng, Andrew M Roberts
1Department of Pediatrics, Kosair Children's Hospital Research Institute, 570 S Preston St., Suite 321, University of Louisville, Louisville, Kentucky 40202, USA.
American Journal of Physiology. Heart and Circulatory Physiology
|September 13, 2005
Summary
Chronic intermittent hypoxia (IH) during development can impair baroreflex function long-term. Postnatal IH in rats reduced vagal projections, leading to decreased baroreflex sensitivity and altered heart rate responses.
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Neuroscience
Background:
- Chronic intermittent hypoxia (IH) during perinatal development is a concern.
- IH may lead to lasting cardiovascular changes by affecting baroreflex control.
- Understanding these long-term effects is crucial for pediatric health.
Purpose of the Study:
- To investigate the long-term impact of perinatal intermittent hypoxia (IH) on baroreflex sensitivity (BRS) and cardiac chronotropic responses in rats.
- To determine if IH exposure during specific developmental windows (prenatal vs. postnatal) differentially affects cardiovascular regulation.
- To explore the underlying neural mechanisms, specifically vagal efferent projections, involved in IH-induced BRS alterations.
Main Methods:
- Rats were exposed to IH or normoxia during prenatal or postnatal development.
- Baroreflex sensitivity and cardiac chronotropic responses were assessed in adulthood using pharmacological challenges (phenylephrine, sodium nitroprusside) under normoxia and acute IH.
- Vagal efferent projections to cardiac ganglia were analyzed using neural tracing techniques in a subset of postnatal IH rats.
Main Results:
- Postnatal IH exposure significantly reduced BRS by approximately 50% in adulthood compared to controls, an effect comparable to acute IH in controls.
- The heart rate response to phenylephrine was blunted in postnatal IH rats, and not further affected by acute IH.
- Prenatal IH exposure did not result in significant long-term alterations in BRS or heart rate responses.
- Postnatal IH led to a marked reduction in vagal efferent nerve terminal density and varicose contacts in cardiac ganglia.
Conclusions:
- Chronic intermittent hypoxia during the postnatal period causes long-lasting impairments in baroreflex function and cardiac chronotropic regulation.
- Reduced vagal efferent projections to cardiac ganglia appear to be a key mechanism underlying these long-term cardiovascular modifications.
- Prenatal IH exposure does not seem to induce similar long-term deficits in baroreflex control.
