Changes of the Bioelectrical Activity and Extracellular Micromilieu in the Central Nervous System During Variations of Local Oxygen Pressure

Speckmann, E.‐J.; Bingmann, D.; Lehmenkühler, A.; Lipinski, H. G.

doi:10.1007/978-3-642-83444-8_15

Cited by 8 publications

(6 citation statements)

References 14 publications

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“…However, these neuronal responses to HBO 2 may be blunted because slices recorded under control conditions are already hyperoxic. Moreover, we are concerned that under control conditions neuronal activity is altered by the high PO 2 (3,5,56) and increased exposure to ROS (26,33,54,55). Previous electrophysiological studies in brain slices found that neuronal activity recorded in medium equilibrated with 21% O 2 is different from neuronal activity recorded in medium equilibrated with 95% O 2 (3,5,56).…”

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confidence: 99%

“…Several studies have reported tissue PO 2 values in brain slices measured with polarographic microelectrodes (3-5, 19-21, 28, 50, 56). These experiments were done to determine the slice thickness that optimized slice viability, as measured by extracellularly recorded field potentials, while ensuring that an anoxic tissue core was avoided (19), or, alternatively, to identify the level of oxygenation in the slice so that electrophysiological data could be correlated with tissue PO 2 during hypoxia (28,50,56) and hyperoxia (3)(4)(5)56). Because PO 2 at any depth in a slice is determined by PO 2 of the perfusate, oxygen diffusion distance into the slice, and oxygen consumption (V O 2 ), tissue PO 2 measurements were also used to determine V O 2 (20,21).…”

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confidence: 99%

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Oxygen measurements in brain stem slices exposed to normobaric hyperoxia and hyperbaric oxygen

Mulkey

Henderson²,

Olson

et al. 2001

Journal of Applied Physiology

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We previously reported (J Appl Physiol 89: 807-822, 2000) that < or =10 min of hyperbaric oxygen (HBO(2); < or = 2,468 Torr) stimulates solitary complex neurons. To better define the hyperoxic stimulus, we measured PO(2) in the solitary complex of 300-microm-thick rat medullary slices, using polarographic carbon fiber microelectrodes, during perfusion with media having PO(2) values ranging from 156 to 2,468 Torr. Under control conditions, slices equilibrated with 95% O(2) at barometric pressure of 1 atmospheres absolute had minimum PO(2) values at their centers (291 +/- 20 Torr) that were approximately 10-fold greater than PO(2) values measured in the intact central nervous system (10-34 Torr). During HBO(2), PO(2) increased at the center of the slice from 616 +/- 16 to 1,517 +/- 15 Torr. Tissue oxygen consumption tended to decrease at medium PO(2) or = 1,675 Torr to levels not different from values measured at PO(2) found in all media in metabolically poisoned slices (2-deoxy-D-glucose and antimycin A). We conclude that control medium used in most brain slice studies is hyperoxic at normobaric pressure. During HBO(2), slice PO(2) increases to levels that appear to reduce metabolism.

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confidence: 99%

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Oxygen measurements in brain stem slices exposed to normobaric hyperoxia and hyperbaric oxygen

Mulkey

Henderson²,

Olson

et al. 2001

Journal of Applied Physiology

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“…The increase in the frequency of periodic discharges shown by neurones in organotypic cultures in response to CO2/H + are consistent with their being presumptive respiratory neurones; 9 in the overwhelming majority of central neurones CO2 and acidosis suppress neural activity. 45 The excitatory effects of CO2/H + on cultured medullary neurones in the region of the ventrolateral respiratory group also indicates that this preparation is a suitable model with which to study rhythm generation in a small piece of tissue. On the basis of histological criteria this tissue retains organotypic cellular arrangements and intact synapses and thus allows the maintenance and development of small neural networks.…”

Section: Discussionmentioning

confidence: 97%

“…6) indicate that transmembrane calcium fluxes may have functional significance for rhythm generation in respiratory neurones as they have in the generation of periodic paroxysmal depolarization of central neurones. 8,45 This assumption is supported (i) by findings of Acker and Richter 1 who have described periodic oscillations of the extracellular calcium concentrations in the vicinity of rhythmically discharging respiratory neurones, (ii) by periodic oscillations of the IFC described here which could be weakened or abolished by cobalt and (iii) by the perturbation of periodic bioelectric activity by dantrolene and thapsigargin (Fig. 7), which are known to block calcium-induced calcium release (CICR)15,32, 33 and Ca 2+ ATPases 15,49 of the endoplasmic reticulum, respectively.…”

Section: Discussionmentioning

confidence: 99%

Rhythm generation in organotypic medullary cultures of newborn rats

Baker

Ballantyne²,

Bingmann³

et al. 1995

Intl J of Devlp Neuroscience

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Organotypic transverse medullary slices (obex level) from six-day-old rats, cultured for two to four weeks in chemically defined medium contained rhythmically discharging neurones which were activated by CO2 and H+. The mechanisms underlying this rhythmicity and the spread of excitation and synaptic transmission within this organotypic tissue were examined by modifying the composition of the external solution. Our findings showed that (1) Exposure to tetrodotoxin (0.2 microM) or to high magnesium (6 mM) and low calcium (0.2 mM) concentrations abolished periodic activity. (2) Neither the blockade of GABAergic potentials with bicuculline methiodide (200 microM) and/or hydroxysaclofen (200 microM) nor the blockade of glycinergic potentials with strychnine hydrochloride (100 microM) abolished rhythmicity. (3) While atropine sulphate (5 microM) was ineffective in modulating periodic discharges nicotine (100 microM) - like CO2-shortened the intervals between the periodic events; hexamethonium (50-100 microM) reduced both periodic and aperiodic activity. (4) Exposure to the NMDA antagonist 2-aminophosphonovaleric acid (50 microM) suppressed periodic events only transiently. In the presence of 2-aminophosphonovaleric acid rhythmicity recovered. However, the AMPA-antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (10-50 microM), abolished periodic activity reversibly within less than 5 min. When 6-cyano-7-nitroquinoxaline-2,3-dione and nicotine were administered simultaneously periodic events persisted for up to 10 min. These findings indicate that synaptic excitatory drive is a prerequisite for the generation of rhythmic discharges of medullary neurones in this preparation. This drive may activate voltage-dependent channels or it may facilitate endogenous cellular mechanisms which initiate oscillations of intracellular calcium concentration. To test the latter possibility (5) calcium antagonists were added to the bath saline. The organic calcium antagonists verapamil and flunarizine (50-100 microM each) and the inorganic calcium antagonists cobalt (2 mM) and magnesium (6 mM) suppressed periodic activity and abolished or weakened the chemosensitivity towards CO2/acidosis. (6) Dantrolene (10 microM). an inhibitor of intracellular calcium release decreased the periodicity, while thapsigargin (2 microM) which blocks endoplasmic Ca(2+)-ATPase, transiently accelerated the occurrence of periodic events. (7) Oscillations of intracellular free calcium concentrations in Fura-2 AM-loaded cells were weakened or abolished by cobalt (2 mM). The results of (5)-(7) indicate that transmembrane calcium fluxes as well as intracellular Ca(2+)-release and -clearance mechanisms are a prerequisite for intracellular free calcium oscillations which may be important in the generation of rhythmic discharges in medullary neurones.

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“…Its short response time (Speckmann et al, 1988) serves well in demonstrating the exchange time of the chamber, while its oxygen consumption is of no consequence, as large gas and fluid volumes are turned over in the presented measurements. This is, of course, not true when measuring in living tissue: oxygen supply via diffusion into a slice will lead to significantly lower pO 2 within the tissue where bioelectric signals are generated, and its demand will compete with the oxygen drain by a polarographic probe.…”

Section: Po 2 Measurementsmentioning

confidence: 94%

Remote switching of temperature, gaseous, and aqueous phase in a low-volume interface chamber for brain slices

Wölfer

Speckmann

Wassmann

et al. 2010

Journal of Neuroscience Methods

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Changes of the Bioelectrical Activity and Extracellular Micromilieu in the Central Nervous System During Variations of Local Oxygen Pressure

Cited by 8 publications

References 14 publications

Oxygen measurements in brain stem slices exposed to normobaric hyperoxia and hyperbaric oxygen

Oxygen measurements in brain stem slices exposed to normobaric hyperoxia and hyperbaric oxygen

Rhythm generation in organotypic medullary cultures of newborn rats

Remote switching of temperature, gaseous, and aqueous phase in a low-volume interface chamber for brain slices

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