Arterial Chemoreception From Molecules to Systems
Arterial chemoreceptors are unique structures which continuously monitor changes in arterial blood oxygen, carbon dioxide, glucose, and acid. Alterations in these gases are almost instantaneously sensed by arterial chemoreceptors and relayed into a
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Neonatal Intermittent Hypoxia Induces Persistent Alteration of Baroreflex in Adult Male Rats Cécile A. Julien, Richard Kinkead, Vincent Joseph, and Aida Bairam
Keywords Neonatal apnea • Cardiovascular regulation
25.1
Introduction
Baroreflex is involved in the regulation of arterial blood pressure (BP). An increase in BP activates vagal inhibitory pathways to decrease heart rate; a concomitant decrease in sympathetic discharge reduces vascular resistance. Both responses reduce BP towards normal value. Conversely, a decrease in BP produces opposite effects to increase heart rate and vascular resistance. We recently showed that adult rats previously exposed to chronic neonatal intermittent hypoxia (n-IH) from postnatal days 3–12 show abnormal cardio-respiratory regulation as indicated by change in ventilation, elevated BP, and attenuated splanchnic nerve activity in response to acute hypoxia (Julien et al. 2010). To explain these results, we proposed that n-IH induces long-term changes of cardiovascular control system that may include a persistent attenuation of the baroreflex. To test this hypothesis, we used the same paradigm of n-IH exposure. At adulthood, we used an anesthetized rat preparation to evaluate the effects of previous exposure to n-IH on (1) BP during changes in peripheral vascular resistances, (2) heart rate (HR) responses to BP changes (cardiac baroreflex) and, (3) splanchnic nerve activity (SNA) in response to BP changes (sympathetic baroreflex).
C.A. Julien (*) • R. Kinkead • A. Bairam Department of Pediatrics, Laval University, Centre de Recherche St-François d’Assise, Hôpital Saint-François d’Assise, 10 rue de l’Espinay, Québec, QC G1L3L5, Canada e-mail: [email protected] V. Joseph Department of Pediatrics, Laval University, Centre de Recherche St-François d’Assise, Hôpital Saint-François d’Assise, 10 rue de l’Espinay, Québec, QC G1L3L5, Canada CRCHUQ/Hop Laval, Québec G0A3X0, Canada C.A. Nurse et al. (eds.), Arterial Chemoreception: From Molecules to Systems, Advances in Experimental Medicine and Biology 758, DOI 10.1007/978-94-007-4584-1_25, © Springer Science+Business Media Dordrecht 2012
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Materials and Methods
Experimental protocol was approved by the Laval University Animal Care Committee. Ten male Sprague–Dawley rats born in our animal care facility from six virgin females (Charles Rivers St-Constant, QC, CA) were exposed to either neonatal intermittent hypoxia (n-IH, nadir 5% O2 in 100 s, every 6 min for 1 h followed by 1 h at 21% O2, repeated 24 h a day) or ambient air (control) for ten consecutive days from postnatal days 3 to 12 as previously described (Julien et al. 2010). At the end of the n-IH exposure, rats were raised under normal conditions until adulthood (3 months old). For BP, HR, and SNA recordings, adult rats were anesthetized using isoflurane (3.5% in 35% O2 balanced nitrogen), tracheotomized, and mechanically ventilated (model 683, Harvard Instruments, Holliston, MA, USA). The end-tidal partial pressure of carbon dioxi
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