Relation between activity‐induced intracellular sodium transients and ATP dynamics in mouse hippocampal neurons

Gerkau, Niklas J.; Lerchundi, Rodrigo; Nelson, Joel S. E.; Lantermann, Marina; Meyer, J.D.; Hirrlinger, Johannes; Rose, Christine R.

doi:10.1113/jp278658

Cited by 42 publications

(44 citation statements)

References 79 publications

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“…Acute slices of mouse hippocampus or neocortex (mus musculus, Balb/C; both sexes) of 250 µm thickness were generated using the methods previously published [30]. In addition, transgenic mice were used which displayed unrestricted deletion of connexin30, as well as Cre-recombinase-dependent deletion of connexin43 [31].…”

Section: Preparation Of Tissue Slicesmentioning

confidence: 99%

“…In accordance with the German animal welfare act (Articles 4 and 7), no formal additional approval for the post-mortem removal of brain tissue was necessary. In accordance with the recommendations of the European Commission [29], animals up to 10 days old were killed by decapitation, while older mice were anaesthetized with CO 2 before the animals were quickly decapitated.Acute slices of mouse hippocampus or neocortex (mus musculus, Balb/C; both sexes) of 250 µm thickness were generated using the methods previously published [30]. In addition, transgenic mice were used which displayed unrestricted deletion of connexin30, as well as Cre-recombinase-dependent deletion of connexin43 [31].…”

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confidence: 99%

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Spontaneous Ultraslow Na+ Fluctuations in the Neonatal Mouse Brain

Felix

Ziemens

Seifert

et al. 2019

Cells

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In the neonate forebrain, network formation is driven by the spontaneous synchronized activity of pyramidal cells and interneurons, consisting of bursts of electrical activity and intracellular Ca2+ oscillations. By employing ratiometric Na+ imaging in tissue slices obtained from animals at postnatal day 2–4 (P2–4), we found that 20% of pyramidal neurons and 44% of astrocytes in neonatal mouse hippocampus also exhibit transient fluctuations in intracellular Na+. These occurred at very low frequencies (~2/h), were exceptionally long (~8 min), and strongly declined after the first postnatal week. Similar Na+ fluctuations were also observed in the neonate neocortex. In the hippocampus, Na+ elevations in both cell types were diminished when blocking action potential generation with tetrodotoxin. Neuronal Na+ fluctuations were significantly reduced by bicuculline, suggesting the involvement of GABAA-receptors in their generation. Astrocytic signals, by contrast, were neither blocked by inhibition of receptors and/or transporters for different transmitters including GABA and glutamate, nor of various Na+-dependent transporters or Na+-permeable channels. In summary, our results demonstrate for the first time that neonatal astrocytes and neurons display spontaneous ultraslow Na+ fluctuations. While neuronal Na+ signals apparently largely rely on suprathreshold GABAergic excitation, astrocytic Na+ signals, albeit being dependent on neuronal action potentials, appear to have a separate trigger and mechanism, the source of which remains unclear at present.

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Section: Preparation Of Tissue Slicesmentioning

confidence: 99%

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confidence: 99%

Spontaneous Ultraslow Na+ Fluctuations in the Neonatal Mouse Brain

Felix

Ziemens

Seifert

et al. 2019

Cells

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“…The aim of this work was to establish a quantitative measurement of changes in intracellular ATP concentration ([ATP]) in organotypic tissue slices of the mouse hippocampus and cortex and to compare the suitability of two different variants of the FRET-based nanosensor ATeam. To this end, we first developed a procedure for the calibration of the high-affinity variant ATeam1.03 YEMK and the lower-affinity probe ATeam1.03 in astrocytes following a strategy recently introduced for neurons (Gerkau et al, 2019). Such calibration in situ requires: (a) a celltype-specific expression of the sensor in astrocytes; (b) a free, unrestricted passage of ATP across cellular plasma membranes;…”

Section: Permeabilization Protocolmentioning

confidence: 99%

“…We next compared the ATP sensitivity of ATeam1.03 YEMK as determined in astrocytes with that of the same sensor when expressed in neurons. To this end, organotypic slices were transduced with an AAV vector hosting the hSyn1 promoter, resulting in a specific neuronal expression of ATeam1.0 YEMK (Figure 3; Gerkau et al, 2019). As observed for astrocytes, incubation with a saline containing β-escin to permeabilize plasma membranes for ATP (see Figure 1, Step II) resulted in a swelling of cells in the upper tissue layers (Figure 3).…”

Section: Atp Sensitivity Of Ateam103 Yemk Expressed In Neuronsmentioning

confidence: 99%

“…The metabolic response to a neuronal activity also seems to differ between both cell types. Different approaches to monitor cellular ATP have suggested that following application of glutamate or induction of electrical activity, neurons experience a decline in intracellular ATP levels (Ainscow et al, 2002;Mollajew et al, 2013;Trevisiol et al, 2017;Gerkau et al, 2019). In astrocytes, but not in neurons, increasing extracellular K + to mimic excitatory neuronal activity results in an increase in ATP levels, consistent with an increase in astrocyte glycolysis (Fernández-Moncada et al, 2018;Lerchundi et al, 2019a).…”

Section: Introductionmentioning

confidence: 98%

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Quantitative Imaging of Changes in Astrocytic and Neuronal Adenosine Triphosphate Using Two Different Variants of ATeam

Lerchundi

Huang

Rose

2020

Front. Cell. Neurosci.

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Genetically encoded nanosensors such as the FRET-based adenosine triphosphate (ATP) sensor ATeam enable the measurement of changes in ATP levels inside cells, promoting our understanding of metabolic interactions between astrocytes and neurons. The sensors are usually well characterized in vitro but display altered properties when expressed inside cells, precluding a meaningful conversion of changes in FRET ratios into changes in intracellular ATP concentrations ([ATP]) on the basis of their in vitro properties. Here, we present an experimental strategy for the intracellular calibration of two different variants of ATeam in organotypic tissue slice culture of the mouse brain. After cell-type-specific expression of the sensors in astrocytes or neurons, slices were first perfused with a saline containing the saponin β-escin to permeabilize plasma membranes for ATP. Next, cells were depleted of ATP by perfusion with ATP-free saline containing metabolic inhibitors. Finally, ATP was re-added at defined concentrations and resulting changes in the FRET ratio recorded. When employing this protocol, ATeam1.03 expressed in astrocytes reliably responds to changes in [ATP], exhibiting an apparent K D of 9.4 mM. The high-affinity sensor ATeam1.03 YEMK displayed a significantly lower intracellular K D of 2.7 mM. On the basis of these calibrations, we found that induction of a recurrent neuronal network activity resulted in an initial transient increase in astrocytic [ATP] by ∼0.12 mM as detected by ATeam1.03 YEMK , a result confirmed using ATeam1.03. In neurons, in contrast, [ATP] immediately started to decline upon initiation of a network activity, amounting to a decrease by an average of 0.29 mM after 2 min. Taken together, our results demonstrate that ATeam1.03 YEMK and ATeam1.03 display a significant increase in their apparent K D when expressed inside cells as compared with in vitro. Moreover, they show that both ATeam variants enable the quantitative detection of changes of astrocytic and neuronal [ATP] in the physiological range. ATeam1.03 YEMK , however, seems preferable because its K D is close to baseline ATP levels. Finally, our data support the idea that synchronized neuronal activity initially stimulates the generation of ATP in astrocytes, presumably through increased glycolysis, whereas ATP levels in neurons decline.

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