Astrocytic glutamate uptake is slow and does not limit neuronal NMDA receptor activation in the neonatal neocortex

Hanson, Elizabeth; Armbruster, Moritz; Cantú, David; Lau, Lauren A.; Taylor, Amaro; Danbolt, Niels Christian; Dulla, Chris G.

doi:10.1002/glia.22844

Cited by 56 publications

(55 citation statements)

References 72 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To address the involvement of glutamate transporter subtypes GLT-1 and GLAST, we performed immunohistochemical stainings and immunoblotting, demonstrating expression of both transporters at the protein level during the first three weeks after birth in corpus callosum. Their expression levels increased between P5 and P25, which is similar to hippocampus and neocortex [43,77].…”

Section: Relevance Of Different Sodium Influx Pathwaysmentioning

confidence: 61%

Action Potential Firing Induces Sodium Transients in Macroglial Cells of the Mouse Corpus Callosum

et al. 2018

View full text Add to dashboard Cite

Recent work has established that glutamatergic synaptic activity induces transient sodium elevations in grey matter astrocytes by stimulating glutamate transporter 1 (GLT-1) and glutamate-aspartate transporter (GLAST). Glial sodium transients have diverse functional consequences but are largely unexplored in white matter. Here, we employed ratiometric imaging to analyse sodium signalling in macroglial cells of mouse corpus callosum. Electrical stimulation resulted in robust sodium transients in astrocytes, oligodendrocytes and NG2 glia, which were blocked by tetrodotoxin, demonstrating their dependence on axonal action potentials (APs). Action potential-induced sodium increases were strongly reduced by combined inhibition of ionotropic glutamate receptors and glutamate transporters, indicating that they are related to release of glutamate. While AMPA receptors were involved in sodium influx into all cell types, oligodendrocytes and NG2 glia showed an additional contribution of NMDA receptors. The transporter subtypes GLT-1 and GLAST were detected at the protein level and contributed to glutamate-induced glial sodium signals, indicating that both are functionally relevant for glutamate clearance in corpus callosum. In summary, our results demonstrate that white matter macroglial cells experience sodium influx through ionotropic glutamate receptors and glutamate uptake upon AP generation. Activity-induced glial sodium signalling may thus contribute to the communication between active axons and macroglial cells.

show abstract

Section: Relevance Of Different Sodium Influx Pathwaysmentioning

confidence: 61%

Action Potential Firing Induces Sodium Transients in Macroglial Cells of the Mouse Corpus Callosum

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Homozygote EAAT2-knockout mice (Tanaka et al, 1997) are inconspicuous at birth because EAAT2 expression is very low in newborn rats and mice (Ullensvang et al, 1997;Furuta et al, 1997;Hanson et al, 2015), but they become spontaneously epileptic at around three weeks of age and about half of them have died by the end of the fourth week (Tanaka et al, 1997;Mitani and Tanaka, 2003;Takasaki et al, 2008). A selective deletion of EAAT2 in the brain is sufficient to reproduce this phenotype confirming that EAAT2 plays its most important role in the brain (Zhou et al, 2014b).…”

Section: Eaat2mentioning

confidence: 97%

“…cutting of slices) may activate connexins (Abudara et al, 2015;Rovegno et al, 2015). However, the combined conductance must be lower than the capacity of the astrocytes to maintain their transmembrane gradients considering that astrocytes in the hippocampal slice preparations are able to maintain their membrane potentials (Bergles and Jahr, 1997; Hanson et al, 2015).…”

Section: A Larger Loss Of D-aspartate From Astrocytes Than From Termimentioning

confidence: 99%

Neuronal vs glial glutamate uptake: Resolving the conundrum

Danbolt

Furness

Zhou

2016

Neurochemistry International

180

152

View full text Add to dashboard Cite

Neither normal brain function nor the pathological processes involved in neurological diseases can be adequately understood without knowledge of the release, uptake and metabolism of glutamate. The reason for this is that glutamate (a) is the most abundant amino acid in the brain, (b) is at the cross-roads between several metabolic pathways, and (c) serves as the major excitatory neurotransmitter. In fact most brain cells express glutamate receptors and are thereby influenced by extracellular glutamate. In agreement, brain cells have powerful uptake systems that constantly remove glutamate from the extracellular fluid and thereby limit receptor activation. It has been clear since the 1970s that both astrocytes and neurons express glutamate transporters. However, the relative contribution of neuronal and glial transporters to the total glutamate uptake activity, however, as well as their functional importance, has been hotly debated ever since. The present short review provides (a) an overview of what we know about neuronal glutamate uptake as well as an historical description of how we got there, and (b) a hypothesis reconciling apparently contradicting observations thereby possibly resolving the paradox. ABBREVIATIONSCre, Cyclization recombinase (Le and Sauer, 2000); EAAC1, glutamate transporter (EAAT3; slc1a1; Kanai and Hediger, 1992; Bjørås et al., 1996); EAAT, excitatory amino acid transporter (synonym to glutamate transporter); GABA, γ-aminobutyric acid; GLAST, rat glutamate transporter (EAAT1; slc1a3; Storck et al., 1992;Tanaka, 1993a); GLT-1, rat glutamate transporter (EAAT2; slc1a2; Pines et al., 1992); GLUL, glutamine synthetase; TBOA, DL-threo-β-benzyloxyaspartate AbstractNeither normal brain function nor the pathological processes involved in neurological diseases can be adequately understood without knowledge of the release, uptake and metabolism of glutamate. The reason for this is that glutamate (a) is the most abundant amino acid in the brain, (b) is at the cross-roads between several metabolic pathways, and (c) serves as the major excitatory neurotransmitter. In fact most brain cells express glutamate receptors and are thereby influenced by extracellular glutamate. In agreement, brain cells have powerful uptake systems that constantly remove glutamate from the extracellular fluid and thereby limit receptor activation. It has been clear since the 1970s that astrocytes and neurons express glutamate transporters. The relative contribution of neuronal and glial transporters to the total glutamate uptake activity, however, as well as their functional importance, has been hotly debated ever since. The present short review provides (a) an overview of what we know about neuronal glutamate uptake as well as an historical description of how we got there, and (b) an hypothesis reconciling apparently contradicting observations thereby possibly resolving the paradox.

show abstract

“…Whole-cell patch clamp recordings were made as described previously (Hanson et al, 2015). Astrocytes were identified 1) in deep cortical layers (layers IV–VI) of the paramicrogyral zone (PMZ), 2) in the microgyral zone, and 3) in isotopic cortical areas of sham-lesioned animals.…”

Section: Methodsmentioning

confidence: 99%

Astrocyte membrane properties are altered in a rat model of developmental cortical malformation but single-cell astrocytic glutamate uptake is robust

Hanson

Danbolt

Dulla

2016

Neurobiology of Disease

Self Cite

View full text Add to dashboard Cite

Developmental cortical malformations (DCMs) are linked with severe epilepsy and are caused by both genetic and environmental insults. DCMs include several neurological diseases, such as focal cortical dysplasia, polymicrogyria, schizencephaly, and others. Human studies have implicated astrocyte reactivity and dysfunction in the pathophysiology of DCMs, but their specific role is unknown. As astrocytes powerfully regulate glutamate neurotransmission, and glutamate levels are known to be increased in human epileptic foci, understanding the role of astrocytes in the pathological sequelae of DCMs is extremely important. Additionally, recent studies examining astrocyte glutamate uptake in DCMs have reported conflicting results, adding confusion to the field. In this study we utilized the freeze lesion (FL) model of DCM, which is known to induce reactive astrocytosis and cause significant changes in astrocyte morphology, proliferation, and distribution. Using whole-cell patch clamp recording from astrocytes, we recorded both UV-uncaging and synaptically evoked glutamate transporter currents (TCs), widely accepted assays of functional glutamate transport by astrocytes. With this approach, we set out to test the hypothesis that astrocyte membrane properties and glutamate transport were disrupted in this model of DCM. Though we found that the developmental maturation of astrocyte membrane resistance was disrupted by FL, glutamate uptake by individual astrocytes was robust throughout FL development. Interestingly, using an immunolabeling approach, we observed spatial and developmental differences in excitatory amino acid transporter (EAAT) expression in FL cortex. Spatially specific differences in EAAT2 (GLT-1) and EAAT1 (GLAST) expression suggest that the relative contribution of each EAAT to astrocytic glutamate uptake may be altered in FL cortex. Lastly, we carefully analyzed the amplitudes and onset times of both synaptically- and UV uncaging-evoked TCs. We found that in the FL cortex, synaptically-evoked, but not UV uncaging-evoked TCs, were larger in amplitude. Additionally, we found that the amount of electrical stimulation required to evoke a synaptic TC was significantly reduced in the FL cortex. Both of these finding are consistent with increased excitatory input to the FL cortex, but not with changes in how individual astrocytes remove glutamate. Taken together, our results demonstrate that the maturation of astrocyte membrane resistance, local distribution of glutamate transporters, and glutamatergic input to the cortex are altered in the FL model, but that single-cell astrocytic glutamate uptake is robust.

show abstract

Astrocytic glutamate uptake is slow and does not limit neuronal NMDA receptor activation in the neonatal neocortex

Cited by 56 publications

References 72 publications

Action Potential Firing Induces Sodium Transients in Macroglial Cells of the Mouse Corpus Callosum

Action Potential Firing Induces Sodium Transients in Macroglial Cells of the Mouse Corpus Callosum

Neuronal vs glial glutamate uptake: Resolving the conundrum

Astrocyte membrane properties are altered in a rat model of developmental cortical malformation but single-cell astrocytic glutamate uptake is robust

Contact Info

Product

Resources

About