Summary: For the first time, researchers have tracked how individual neurons lose and then recover their energy during spreading depolarizations — propagating waves of electrical disturbance that occur in a range of brain disorders and are strongly associated with stroke and cerebral ischemia. Using genetically modified mice and high-resolution fluorescence microscopy, the team visualized adenosine triphosphate (ATP) dynamics in single neurons under both normal and stroke-like conditions, revealing when and how neuronal energy stores become depleted and, importantly, when they can be restored.
Spreading depolarizations produced a transient but substantial drop in neuronal ATP in healthy tissue and caused an accelerated, terminal ATP decline when oxygen and glucose were restricted to simulate ischemia. Crucially, when oxygen and glucose were promptly reintroduced, most neurons were able to regenerate ATP, indicating that energy collapse triggered by these waves can be reversible if metabolic support is restored in time.
Key Facts:
- Direct real-time imaging: ATP depletion in single neurons was visualized during spreading depolarizations using a fluorescent sensor.
- Reversibility: Most neurons could restore ATP levels after depolarization when glucose and oxygen were re-supplied, indicating potential for recovery.
- Stroke-like acceleration: Under oxygen and glucose deprivation, spreading depolarizations accelerated ATP exhaustion and led to a large, often terminal, drop in neuronal energy.
Source: University of Leipzig
Research team and context: Scientists at the Carl Ludwig Institute for Physiology at Leipzig University developed a mouse model in which neurons express a fluorescent ATP sensor, enabling observation of intracellular ATP concentrations with subcellular resolution. Combining this genetically encoded reporter with two-photon and high-resolution fluorescence microscopy, the investigators recorded ATP signals in individual neurons while simultaneously monitoring electrophysiological markers of spreading depolarizations.
The study was published in the journal PNAS. Adenosine triphosphate (ATP) is the primary energy carrier in neurons. By imaging an ATP-sensitive fluorescent protein (ATeam1.03YEMK) expressed in neurons, the researchers could monitor ATP changes in real time during spreading depolarizations induced either by elevated extracellular potassium or by oxygen–glucose deprivation (OGD), a common experimental model of cerebral ischemia.
Spreading depolarizations are waves of near-complete neuronal depolarization that propagate through brain tissue, increasing metabolic demand and oxygen consumption. While these events are known to aggravate tissue damage after stroke, direct measurements of intracellular neuronal ATP during spreading depolarizations had not previously been available. This work fills that gap by showing that spreading depolarizations transiently increase ATP consumption beyond production, producing a measurable drop in intracellular ATP in otherwise healthy tissue and a catastrophic ATP collapse under ischemic conditions.
“Our study provides the first high-resolution view of when and how neurons exhaust their energy reserves during acute mismatches between supply and demand, such as in stroke,” said Dr. Karl Schoknecht, lead author from the Carl Ludwig Institute for Physiology. The researchers emphasize that ATP loss is not uniform across cells but closely tied to the timing and propagation of spreading depolarizations. The experimental model will be used in future projects to test interventions aimed at preventing or mitigating the severe energy loss these waves trigger.
In experiments simulating stroke by removing glucose and oxygen from the bathing solution, the investigators recorded spreading depolarizations with local field potential measurements, extracellular potassium recordings, and intrinsic optical signals. Under those ischemic conditions, a slight ATP reduction present before depolarization became a large, often irreversible collapse during spreading depolarizations. However, when oxygen and glucose were promptly restored after detection of a depolarization, most neurons regenerated ATP, demonstrating that the metabolic collapse can be reversible if perfusion and metabolic substrates are re-established quickly.
The work integrates complementary expertise within the Carl Ludwig Institute: advanced microscopy methods led by Professor Jens Eilers, development of tailored mouse models by Professor Johannes Hirrlinger, and experimental studies of spreading depolarizations by Dr. Karl Schoknecht. Together, these approaches deliver a new experimental platform to evaluate therapeutic strategies that target spreading depolarizations after cerebral ischemia.
About this neuroscience research news
Author: Carsten Heckmann
Source: University of Leipzig
Contact: Carsten Heckmann – University of Leipzig
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Spreading depolarizations exhaust neuronal ATP in a model of cerebral ischemia” by Karl Schoknecht et al., PNAS. DOI: 10.1073/pnas.2415358122
Abstract
Spreading depolarizations exhaust neuronal ATP in a model of cerebral ischemia
Spreading depolarizations (SDs) occur in multiple brain pathologies and impose a marked increase in cerebral energy demand and oxygen consumption, reflecting enhanced ATP turnover by oxidative phosphorylation. Because SDs raise metabolic requirements, they are particularly harmful when oxygen and glucose supply is reduced. Until now, direct measurements of intracellular neuronal ATP ([ATP]i), which report the dynamic balance of ATP production and consumption during SDs, had not been performed.
Using two-photon imaging in acute brain slices from adult mice expressing the neuronal ATP sensor ATeam1.03YEMK, SDs were evoked by potassium chloride application or by oxygen–glucose deprivation and were detected simultaneously by local field potential recording, extracellular potassium monitoring, and intrinsic optical signals. In the presence of oxygen and glucose, SDs produced a substantial but transient decrease in neuronal ATP sensor signals, corresponding to temporary ATP depletion. Under oxygen–glucose deprivation, a modest ATP reduction prior to SDs was followed by a pronounced, often terminal, ATP collapse during SDs.
When oxygen and glucose were promptly reintroduced after SD detection, ATP depletion proved largely reversible in most cells. These results indicate that SDs drive ATP consumption beyond production and, under conditions that mimic reduced blood supply, can precipitate intracellular ATP breakdown. The findings support therapeutic approaches aimed at preventing or limiting spreading depolarizations in the context of cerebral ischemia.