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Marie-Laure Specq, Mélisande Bourgoin-Heck, Nathalie Samson, François Corbin, Christian Gestreau, Maxime Richer, Hazim Kadhim, Jean-Paul Praud
Hyperbilirubinemia (HB) occurs in 90% of preterm newborns. Moderate HB can induce acute neurological disorders while severe HB has been linked to a higher incidence of apneas of prematurity. The present study aimed to test the hypothesis that even moderate HB disrupts cardiorespiratory control in preterm lambs. Two groups of preterm lambs (born 14 days prior to term), namely control (n = 6) and HB (n = 5), were studied. At day 5 of life, moderate HB (150-250 μmol/L) was induced during 17 h in the HB group after which cardiorespiratory control as well as laryngeal and pulmonary chemoreflexes were assessed during baseline recordings and during hypoxia...
2016: Frontiers in Physiology
Jianguo Zhuang, Xiuping Gao, Franklin Gao, Fadi Xu
We tested the hypothesis that mu-opioid receptors (MORs) in the caudomedial nucleus tractus solitarius (cmNTS) are important for the ventilatory responses to stimulation of bronchopulmonary C-fibers (PCFs), the carotid body-mediated hypoxia, and hypercapnia independent of the carotid body. First, we used immunohistochemistry to map MORs distribution in the caudal medulla. Then we compared the effects of intra-cmNTS microinjection of DAMGO (a MOR agonist) with or without a combination of CTAP (a MOR antagonist) on the ventilatory responses to: 1) right atrial injection of capsaicin (to stimulation of PCFs) and 2) acute hypoxia (HVR, to stimulate the carotid body) in awake intact rats; and 3) hypercapnia (HCVR) in the carotid body ablated rats...
October 12, 2016: Respiratory Physiology & Neurobiology
Wioletta Pijacka, Fiona McBryde, Anthony P Ford, Julian F R Paton
OBJECTIVE: Arterial hypertension is associated with increases in both peripheral chemoreceptor reflex sensitivity and sympathetic nerve activity (SNA). We have shown that CB resection in SH rats reduces arterial pressure (AP; McBryde et al. 2013). Since P2X3 receptors exist in the rat CB and P2X3 receptor activity is associated with afferent hyperreflexia (Ford et al. 2015), we hypothesized that P2X3 receptor would be upregulated in the CB of SH vs normotensive (Wistar) control rats and that a selective P2X3 receptor antagonist (AF-219) would reduce chemoreflex hypersensitivity, AP and SNA in SH rats...
September 2016: Journal of Hypertension
Leonardo T Totola, Ana C Takakura, José Antonio C Oliveira, Norberto Garcia-Cairasco, Thiago S Moreira
Respiratory disorders may involve changes in serotonergic neurotransmission at the level of the chemosensitive neurons located in the retrotrapezoid nucleus (RTN). Here, we investigated the central respiratory chemoreflex and the role of serotonergic neurotransmission in the RTN with a rat model of tonic-clonic seizures, the Wistar Audiogenic Rat (WAR). We found that naïve or kindled WAR animals have reduced resting ventilation and ventilatory response to hypercapnia (7% CO2 ). The number of chemically-coded (Phox2b(+) /TH(-) ) RTN neurons, as well as the serotonergic innervation to the RTN, was reduced in WARs...
September 16, 2016: Journal of Physiology
Kun-Ze Lee, Hsiang-Chun Kuo
The present study was designed to establish a midcervical contusion model that can simulate long-term respiratory deficits, and investigate the breathing pattern during vagal-mediated respiratory reflexes following midcervical contusion. Moderate and severe (impactor height: 6.25 or 12.5 mm) contusion was induced at midline C3-4 spinal cord in adult Sprague-Dawley rats. The ventilatory behaviors of unanesthetized were evaluated by whole body plethysmography at 1 day and 1, 2, 4, and 8 weeks post-injury. The tidal volume was decreased and frequency was increased in contused animals compared with uninjured animals at the acute injury state...
October 13, 2016: Journal of Neurotrauma
Christina D Bruce, Craig D Steinback, Uday V Chauhan, Jamie R Pfoh, Maria Abrosimova, Emily R Vanden Berg, Rachel J Skow, Margie H Davenport, Trevor A Day
The central respiratory chemoreflex contributes to blood gas homeostasis, particularly in response to accumulation of brainstem CO2 . Cerebrovascular reactivity (CVR) affects chemoreceptor stimulation inversely through CO2 washout from brainstem tissue. Voluntary breath-holding imposes alterations in blood gases, eliciting respiratory chemoreflexes, potentially contributing to breath-hold duration (i.e., break-point). However, the effects of cerebrovascular reactivity on break-point have yet to be determined...
September 12, 2016: Experimental Physiology
Alberto Giannoni, Michele Emdin, Claudio Passino
No abstract text is available yet for this article.
September 8, 2016: New England Journal of Medicine
Amy T Bascom, Abdulghani Sankari, M Safwan Badr
Sleep-disordered breathing (SDB) is prevalent in individuals with chronic spinal cord injury (SCI), but the exact mechanism is unknown. The aim of this study was to investigate whether peripheral chemoreceptors activity is enhanced in individuals with chronic SCI compared to abled-bodied control subjects using CO2 and O2 chemical tests. In protocol (1) 30 subjects (8 cervical [cSCI], 7 thoracic [tSCI] and 15 able-bodied [AB]) were studied to determine the ventilatory response to hyperoxia during wakefulness in the supine position...
September 2016: Physiological Reports
Barbara J Morgan, Melissa L Bates, Rodrigo Del Rio, Zunyi Wang, John M Dopp
Chronic exposure to intermittent hypoxia (CIH) elicits plasticity of the carotid sinus and phrenic nerves via reactive oxygen species (ROS). To determine whether CIH-induced alterations in ventilation, metabolism, and heart rate are also dependent on ROS, we measured responses to acute hypoxia in conscious rats after 14 and 21 d of either CIH or normoxia (NORM), with or without concomitant administration of allopurinol (xanthine oxidase inhibitor), combined allopurinol plus losartan (angiotensin II type 1 receptor antagonist), or apocynin (NADPH oxidase inhibitor)...
September 2, 2016: Respiratory Physiology & Neurobiology
D A Giussani
No abstract text is available yet for this article.
September 1, 2016: Journal of Physiology
Mieczyslaw Pokorski, Kotaro Takeda, Yasumasa Okada
This review tackles the unresolved issue of the existence of oxygen sensor in the body. The sensor that would respond to changes in tissue oxygen content, possibly along the hypoxia-normoxia-hyperoxia spectrum, rather than to a given level of oxygen, and would translate the response into lung ventilation changes, the major adaptive process. Studies on oxygen sensing, for decades, concentrated around the hypoxic ventilatory response generated mostly by carotid body chemoreceptor cells. Despite gaining a substantial insight into the cellular transduction pathways in carotid chemoreceptors, the exact molecular mechanisms of the chemoreflex have never been conclusively verified...
August 30, 2016: Advances in Experimental Medicine and Biology
Scott A Sands, Yoseph Mebrate, Bradley A Edwards, Shamim Nemati, Charlotte H Manisty, Akshay S Desai, Andrew Wellman, Keith Willson, Darrel P Francis, James P Butler, Atul Malhotra
RATIONALE: In patients with chronic heart failure, daytime oscillatory breathing at rest is associated with high mortality risk. Experimental evidence, including exaggerated ventilatory responses to carbon dioxide (CO2) and prolonged circulation time, implicates the ventilatory control system and suggests feedback instability (loop gain>1) is responsible. However, daytime oscillatory patterns often appear remarkably irregular versus classical instability (Cheyne-Stokes respiration), suggesting our mechanistic understanding is limited...
August 25, 2016: American Journal of Respiratory and Critical Care Medicine
Wioletta Pijacka, Fiona D McBryde, Paul J Marvar, Gisele S Lincevicius, Ana Pl Abdala, Lavinia Woodward, Dan Li, David J Paterson, Julian Fr Paton
The peripheral chemoreflex is known to be hyper-responsive in both spontaneously hypertensive (SHR) and Goldblatt hypertensive (2 kidney 1 clip; 2K1C) rats. We have previously shown that carotid sinus nerve denervation (CSD) reduces arterial blood pressure (ABP) in SHR. Here, we show that CSD ameliorates 2K1C hypertension and reveal potential underlying mechanisms. Adult Wistar rats were instrumented to record ABP via telemetry, then underwent CSD (n = 9) or sham CSD (n = 9) five weeks after renal artery clipping, versus normal Wistar (n = 5)...
August 11, 2016: Journal of Physiology
Fernanda C Silva, Franciny A Paiva, Flávia C Müller-Ribeiro, Henrique M A Caldeira, Marco A P Fontes, Rodrigo C A de Menezes, Karina R Casali, Gláucia H Fortes, Eleonora Tobaldini, Monica Solbiati, Nicola Montano, Valdo J Dias Da Silva, Deoclécio A Chianca
A low resting heart rate (HR) would be of great benefit in cardiovascular diseases. Ivabradine-a novel selective inhibitor of hyperpolarization-activated cyclic nucleotide gated (HCN) channels- has emerged as a promising HR lowering drug. Its effects on the autonomic HR control are little known. This study assessed the effects of chronic treatment with ivabradine on the modulatory, reflex and tonic cardiovascular autonomic control and on the renal sympathetic nerve activity (RSNA). Male Wistar rats were divided in 2 groups, receiving intraperitoneal injections of vehicle (VEH) or ivabradine (IVA) during 7 or 8 consecutive days...
2016: Frontiers in Physiology
N A Baertsch, T L Baker
Two critical parameters that influence breathing stability are the levels of arterial pCO2 at which breathing ceases and subsequently resumes - termed the apneic and recruitment thresholds (AT and RT, respectively). Reduced respiratory neural activity elicits a chemoreflex-independent, long-lasting increase in phrenic burst amplitude, a form of plasticity known as inactivity-induced phrenic motor facilitation (iPMF). The physiological significance of iPMF is unknown. To determine if iPMF and neural apnea have long-lasting physiological effects on breathing, we tested the hypothesis that patterns of neural apnea that induce iPMF also elicit changes in the AT and RT...
July 26, 2016: Experimental Neurology
Nanduri R Prabhakar
What is the topic of this review? This article presents emerging evidence for heightened carotid body chemoreflex activity as a major driver of sympathetic activation and hypertension in sleep apnoea patients. What advances does it heighlight? This article discusses the recent advances on cellular, molecular and epigenetic mechanisms underlying the exaggerated chemoreflex in experimental models of sleep apnoea. The carotid bodies are the principal peripheral chemoreceptors for detecting changes in arterial blood oxygen concentration, and the resulting chemoreflex is a potent regulator of the sympathetic tone, blood pressure and breathing...
August 1, 2016: Experimental Physiology
Ryma Boukari, Orlane Rossignol, Cécile Baldy, François Marcouiller, Aida Bairam, Vincent Joseph
We tested the hypothesis that membrane progesterone receptors (mPR) contribute to respiratory control in adult male and female mice. Mice were implanted with osmotic minipumps for continuous infusion of small interfering RNA (siRNA) directed against mPRα, mPRβ, or a control solution in the 4(th) ventricle (to target brainstem respiratory areas) for 14 days. We then performed respiratory and metabolic recordings by whole body plethysmography at rest, and in response to hypoxia (12% O2) or hypercapnia (5% CO2 - 5 minutes each)...
July 28, 2016: Journal of Applied Physiology
Seung Jae Kim, Paul M Pilowsky, Melissa M J Farnham
Intermittent hypoxia causes a persistent increase in sympathetic nerve activity (SNA), which progresses to hypertension in conditions such as obstructive sleep apnea. Orexins (A and B) are hypothalamic neurotransmitters with arousal-promoting and sympathoexcitatory effects. We investigated whether the sustained elevation of SNA, termed sympathetic long-term facilitation, after acute intermittent hypoxia (AIH) is caused by endogenous orexin acting on spinal sympathetic preganglionic neurons. The role of orexin in the increased SNA response to AIH was investigated in urethane-anesthetized, vagotomized, and artificially ventilated Sprague-Dawley rats (n = 58)...
September 2016: Journal of Pharmacology and Experimental Therapeutics
Rodrigo Del Rio, David C Andrade, Claudia Lucero, Paulina Arias, Rodrigo Iturriaga
Chronic intermittent hypoxia (CIH), the main feature of obstructive sleep apnea, enhances carotid body (CB) chemosensory responses to hypoxia and produces autonomic dysfunction, cardiac arrhythmias, and hypertension. We tested whether autonomic alterations, arrhythmogenesis, and the progression of hypertension induced by CIH depend on the enhanced CB chemosensory drive, by ablation of the CB chemoreceptors. Male Sprague-Dawley rats were exposed to control (Sham) conditions for 7 days and then to CIH (5% O2, 12/h 8 h/d) for a total of 28 days...
August 2016: Hypertension
Kevin J Cummings
No abstract text is available yet for this article.
July 1, 2016: Experimental Physiology
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