Developmental changes in the hypoxia tolerance of the in vitro respiratory network of rats

Ballanyi, Klaus; Kuwana, S.; Völker, Antje; Morawietz, Gabriela; Richter, Diethelm W.

doi:10.1016/0304-3940(92)90824-q

Cited by 49 publications

(29 citation statements)

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“…These data are in agreement with current notions regarding the age-related peculiarities of thermoregulation in the rat [5] and the ability of newborn animals to lower the rate of tissue respiration during hypoxia [4,5] and to use ATP for anaerobic glycolysis [7]. As is shown in Table 2, at the 35th min of increasing hypoxia the content of 2,3-DPG in the erythrocytes of adult rats had increased by 23%, while the ATP concentration had fallen by 25%.…”

Section: Resultssupporting

confidence: 93%

Content of 2,3-diphosphoglycerate and adenosine triphosphate in erythrocytes and the acid-base balance in adult and newborn rats during acute hypoxia

et al. 1995

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It is shown that in deep acute hypoxic hypoxia the 2,3-diphosphoglycerate content is reduced and the adenosine triphosphate content unchanged in the erythrocytes of newborn rats. Under the same conditions adult animals show an increase of 2,3-diphosphoglycerate and a drop in the adenosine triphosphate content in the erythrocytes. The importance of these changes is discussed in terms of the mechanisms regulating the oxygen-transporting function of erythrocytes during acute hypoxic hypoxia in newborn and adult animals.

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Section: Resultssupporting

confidence: 93%

Content of 2,3-diphosphoglycerate and adenosine triphosphate in erythrocytes and the acid-base balance in adult and newborn rats during acute hypoxia

et al. 1995

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“…It has been demonstrated that limitation of oxygen diffusion results in an anoxic core, leading to tissue gradients of extracellular K+ and pH [5,20]. Nevertheless, it was shown that neurons of the ventral respiratory group (VRG), which is responsible for rhythm generation [10], are under aerobic conditions [2,5]. Although not studied in detail previously, it was generally agreed that a glucose concentration of 30 mM in the superfusion fluids is essential to provide sufficient substrate for utilization by the respiratory neurons [26].…”

Section: Introductionmentioning

confidence: 98%

“…The functional relevance of anaerobic metabolism was studied by exposure to anoxia after lowering the glucose concentration or during addition of iodoacetate, a blocker of anaerobic glycolysis [23,33]. In superfusates containing 30 mM glucose, experimentally induced anoxia of the entire en bloc preparation does not severely impair ion homeostasis, and respiratory activity persists for more than 1 h at a reduced frequency [2,5,24,31]. The results show that glucose levels of 10 mM are not sufficient to provide long-term maintenance of respiratory network function or protection from anoxic insults.…”

Section: Introductionmentioning

confidence: 99%

Functional relevance of anaerobic metabolism in the isolated respiratory network of newborn rats

1996

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Respiratory (C3-C5) activity and extracellular K+, pH and Ca2+ (aKe, pHe, [Ca]e, respectively) in the ventral respiratory group (VRG) were measured in vitro. In brainstem-spinal cord preparations from 0- to 1-day-old rats, lowering of bath glucose content from 30 to 10 mM for 1 h did not affect aKe or rhythmic activity. In preparations from 2- to 3-day-old animals, however, an aKe rise by about 1 mM and disturbance of rhythm occurred after a delay of 50 min. Glucose-free saline resulted, after about 30 min, in reversible blockade of respiratory rhythm and an aKe rise by more than 8 mM, whereas pHe remained unaffected. Exposure to anoxia for 30 min after 1 h of pre-incubation in 10 mM glucose led to a progressive rise of aKe, and a fall of [Ca]e. The concomitant suppression of rhythm was irreversible in preparations from 2- to 3-day-old animals. Similar effects on aKe and [Ca]e and irreversible blockade of rhythm were revealed during anoxia in glucose-free solution, or by addition of 2-5 mM iodoacetate to oxygenated or hypoxic solutions. Iodoacetate led to a slow increase of pHe by more than 0.2 pH units, which was accelerated by anoxia. Our findings show that normal respiratory network functions in the en bloc medulla, in particular from rats older than 1 day, depend on high bath glucose levels, necessary for effective utilization of anaerobic metabolism.

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“…However, these effects, if any, are probably only likely in the mature animals since in neonatal rats central chemoreceptor activity was not found to be effective compared with adults (Ballanyi, Kuwana, Volker, Morawietz & Richter, 1992). activity (rootlet, n = 3; unitary, n = 7), respectively ( Fig.…”

Section: Sensitivity Of Maturing Respiratory Network To Glycine and Gmentioning

confidence: 99%

Role of fast inhibitory synaptic mechanisms in respiratory rhythm generation in the maturing mouse.

Paton

Richter

1995

The Journal of Physiology

106

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1. The importance of glycinergic and GABAAergic synaptic mechanisms for respiratory rhythm generation in the maturing mouse were investigated in vivo and in an in vitro slice preparation generating respiratory rhythmic activity spontaneously at all postnatal ages. 2. The effect on respiration of topical application of strychnine or bicuculline to the surface of the ventrolateral medulla was assessed in spontaneously breathing anaesthetized mice of different ages (postnatal (P) days 0 to >56). Glycine receptor antagonization with concentrations of strychnine up to 25 uM was ineffective in altering the breathing pattern in neonates (P1-PS) . However, in mature mice (P > 15), low doses of strychnine (0f2-2 uM) abolished regular rhythmic discharge in the phrenic nerve. Bicuculline (0 5-50 /M) produced dose-dependent increases in inspiratory time, amplitude and cycle length of phrenic nerve discharge in anaesthetized neonatal mice whereas both cycle length and duration of inspiratory activity were reduced in mature animals. In addition, in both neonates and mature mice low concentrations of bicuculline (0 5-5 /M) abolished phrenic nerve discharge intermittently. 3. The response of respiratory-modulated hypoglossal (XII) neurones recorded in tilted sagittal slices from newborn and mature mice during blockade of glycine and GABAA receptors was similar to the phrenic nerve changes observed in vivo: in slices from neonates, the rhythmic activity of XII neurones was resistant to concentrations of strychnine up to 50/uM whereas low doses of strychnine (02-2 /M) abolished rhythmic activity in preparations from mature mice. Bicuculline (1-50 /M) produced a dosedependent prolongation of burst duration and a slowing of rhythmic discharge in slices from neonatal mice whereas in mature mice rhythmic XII bursts were shortened and their frequency increased. At all maturational stages, bicuculline (1-50,UM) induced severe disruption of the regular rhythm of XII neurone activity causing maintained depolarizations and oscillations in membrane potential. 4. On-going inhibitory postsynaptic potentials of neurones located in the ventral respiratory group region of tilted sagittal slices from both immature and mature mice were sensitive to low concentrations of either bicuculline or strychnine (1-5 /M) indicating an absence of a maturational change in the sensitivity of GABAA and glycine receptors to their respective antagonists.5. We conclude that over the first 15 days of life in the mouse there is a dramatic increase in the relevance of glycine receptors for respiratory rhythm generation, and change in the functional role of GABAA receptors within the respiratory network, which may provide a stabilizing influence on neurones within the respiratory network from birth onwards.The underlying neural mechanisms for respiratory synaptic mechanisms within the mammalian nervous rhythm generation may be quite different in newborn and system during the first weeks of life. An increase in adult mammals. Indeed, there is a wealth of information p...

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Developmental changes in the hypoxia tolerance of the in vitro respiratory network of rats

Cited by 49 publications

References 11 publications

Content of 2,3-diphosphoglycerate and adenosine triphosphate in erythrocytes and the acid-base balance in adult and newborn rats during acute hypoxia

Content of 2,3-diphosphoglycerate and adenosine triphosphate in erythrocytes and the acid-base balance in adult and newborn rats during acute hypoxia

Functional relevance of anaerobic metabolism in the isolated respiratory network of newborn rats

Role of fast inhibitory synaptic mechanisms in respiratory rhythm generation in the maturing mouse.

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