Glucose homoeostasis in rats exposed to acute intermittent hypoxia

Aim: Chronic exposure to intermittent hypoxia commonly induces the activation of sympathetic tonus and the disruption of glucose homoeostasis. However, the effects of exposure to acute intermittent hypoxia (AIH) on glucose homoeostasis are not yet fully elucidated. Herein, we evaluated parameters related to glucose metabolism in rats exposed to AIH. Methods: Male adult rats were submitted to 10 episodes of hypoxia (6% O2, for 45 s) interspersed with 5-min intervals of normoxia (21%), while the control (CTL) group was kept in normoxia. Results: Acute intermittent hypoxia rats presented higher fasting glycaemia, normal insulinaemia, increased lactataemia and similar serum lipid levels, compared to controls (n = 10, P < 0.05). Additionally, AIH rats exhibited increased glucose tolerance (GT) (n = 10, P < 0.05) and augmented insulin sensitivity (IS) (n = 10, P < 0.05). The p-Akt/Akt protein ratio was increased in the muscle, but not in the liver and adipose tissue of AIH rats (n = 6, P < 0.05). The elevated glycaemia in AIH rats was associated with a reduction in the hepatic glycogen content (n = 10, P < 0.05). Moreover, the AIH-induced increase in blood glucose concentration, as well as reduced hepatic glycogen content, was prevented by prior systemic administration of the β-adrenergic antagonist (P < 0.05). The effects of AIH on glycaemia and Akt phosphorylation were transient and not observed after 60 min. Conclusions: We suggest that AIH induces an increase in blood glucose concentration as a result of hepatic glycogenolysis recruitment through sympathetic activation. The augmentation of GT and IS might be attributed, at least in part, to increased β-adrenergic sympathetic stimulation and Akt protein activation in skeletal muscles, leading to a higher glucose availability and utilization. © 2013 Scandinavian Physiological Society.

Coupling of respiratory and sympathetic activities in rats submitted to chronic intermittent hypoxia

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Effects of acute intermittent hypoxia on sympathetic and expiratory activities in rats

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Atualização em síndrome da apnéia obstrutiva do sono na infância

A prevalência de SAOS em crianças é de 0,7-3%, com pico de incidência nos pré-escolares. Fatores anatômicos (obstrução nasal severa, más-formações craniofaciais, hipertrofia do tecido linfático da faringe, anomalias laríngeas, etc.) e funcionais (doenças neuromusculares) predispõem à SAOS na infância. A principal causa da SAOS em crianças é a hipertrofia adenotonsilar. As manifestações clínicas mais comuns são: ronco noturno, pausas respiratórias, sono agitado e respiração bucal. A oximetria de pulso noturna, a gravação em áudio ou vídeo dos ruídos respiratórios noturnos e a polissonografia breve diurna são métodos úteis para triagem dos casos suspeitos de SAOS em crianças, e o padrão-ouro para diagnóstico é a polissonografia em laboratório de sono durante uma noite inteira. Ao contrário dos adultos com SAOS, as crianças costumam apresentar: menos despertares associados aos eventos de apnéia, maior número de apnéias/hipopnéias durante o sono REM e dessaturação mais acentuada da oxihemoglobina mesmo nas apnéias de curta duração. O tratamento da SAOS pode ser cirúrgico (adenotonsilectomia, correção de anomalias craniofaciais, traqueostomia) ou clínico (higiene do sono, pressão positiva contínua nas vias aéreas - CPAP).

Monitorização ambulatorial da pressão arterial (MAPA) em crianças com distúrbios respiratórios obstrutivos pré e após adenotonsilectomia

Pós-graduação em Bases Gerais da Cirurgia - FMB

Função pulmonar em indivíduos com SAOS antes e após o uso do CPAP: estudo randomizado duplo cego

Pós-graduação em Bases Gerais da Cirurgia - FMB

Peripheral chemoreceptors and cardiorespiratory coupling: a link to sympatho-excitation

Chronic intermittent hypoxia (CIH) has been identified as a relevant risk factor for the development of enhanced sympathetic outflow and arterial hypertension. Several studies have highlighted the importance of peripheral chemoreceptors for the cardiovascular changes elicited by CIH. However, the effects of CIH on the central mechanisms regulating sympathetic outflow are not fully elucidated. Our research group has explored the hypothesis that the enhanced sympathetic drive following CIH exposure is, at least in part, dependent on alterations in the respiratory network and its interaction with the sympathetic nervous system. In this report, I discuss the changes in the discharge profile of baseline sympathetic activity in rats exposed to CIH, their association with the generation of active expiration and the interactions between expiratory and sympathetic neurones after CIH conditioning. Together, these findings are consistent with the theory that mechanisms of central respiratory–sympathetic coupling are a novel factor in the development of neurogenic hypertension.

Electrophysiological properties of rostral ventrolateral medulla presympathetic neurons modulated by the respiratory network in rats

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Physiological and pathophysiological interactions between the respiratory central pattern generator and the sympathetic nervous system

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Coupling between respiratory and sympathetic activities as a novel mechanism underpinning neurogenic hypertension

Enhanced sympathetic outflow to the heart and resistance vessels greatly contributes to the onset and maintenance of neurogenic hypertension. There is a consensus that the development of hypertension (clinical and experimental) is associated with an impairment of sympathetic reflex control by arterial baroreceptors. More recently, chronic peripheral chemoreflex activation, as observed in obstructive sleep apnea, has been proposed as another important risk factor for hypertension. In this review, we present and discuss recent experimental evidence showing that changes in the respiratory pattern, elicited by chronic intermittent hypoxia, play a key role in increasing sympathetic activity and arterial pressure in rats. This concept parallels results observed in other models of neurogenic hypertension, such as spontaneously hypertensive rats and rats with angiotensin II–salt-induced hypertension, pointing out alterations in the central coupling of respiratory and sympathetic activities as a novel mechanism underlying the development of neurogenic hypertension.

The breathing pattern and the ventilatory response to aquatic and aerial hypoxia and hypercarbia in the frog Pipa carvalhoi

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Short-term sustained hypoxia induces changes in the coupling of sympathetic and respiratory activities in rats

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Effect of intermittent feeding on growth in early juveniles of the crayfish Cherax quadricarinatus

Three experiments were conducted with juveniles of the crayfish Cherax quadricarinatus to investigate the effect of intermittent feeding regimes on growth and the ability to tolerate the shortage of food. In experiment 1, stage III juveniles were assigned to one of seven intermittent feeding groups (from FS1: 1 day fed/1 day non-fed to FS7: 7 days fed/7 days non-fed) and two control groups, continuously fed (CF) and continuously starved (CS) animals; this experiment comprised a short-term intermittent feeding period until the first molt, followed by a continuous feeding period. In the experiment 2, stage III juveniles were assigned to one of three intermittent feeding groups (FS2 to FS4) and one control group (CF); it consisted of a prolonged intermittent feeding period, until the end of the experiment In the experiment 3, stage VI and VII juveniles were assigned to one of three intermittent feeding groups (FS2 to FS4) and one control (CF); it also consisted of a prolonged intermittent feeding period. The red claw crayfish juveniles were able to tolerate periods of intermittent feeding and underwent compensatory growth after continuous feed was re-established. The ability of crayfish to tolerate intermittent feeding was influenced by developmental stage and duration of the intermittent feeding period. Stage III juveniles survived, but decreased growth, when subjected to prolonged intermittent feeding. However, they showed full compensatory growth when the intermittent feeding period was short and followed by continuous feeding. on the other hand, stage VI-VII tolerated 60 days of prolonged intermittent feeding without any change in growth and survival. The hepatosomatic index (based on wet weight) values of the treatments and the control were similar, suggesting that intermittent feeding may not be considered a nutritional stress condition. The relative pleon weight (based on wet weight) values of the treatments and control were similar suggesting low use of nutrients from the muscle to increase the chance for survival. The juveniles of C quadricarinatus can tolerate relatively long periods of low food availability and this is an important adaptation for their survival in changing/unpredictable environments and an attribute favorable for the production of the species. (C) 2011 Elsevier B.V. All rights reserved.

Physiological response of American bullfrog tadpoles to stressor conditions of capture and hypoxia

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Profile of cortisol, glycaemia, and blood parameters of American Bullfrog tadpoles Lithobates catesbeianus exposed to density and hypoxia stressors

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