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Updated: May 4, 2026
Simultaneous Photothrombosis and Fiber Photometry to Induce and Monitor Ischemic Stroke in Behaving Mice
Published on: November 14, 2025
Ischemia-induced cell depolarization: does the hyperpolarization-activated cation channel HCN2 affect the outcome
Petra Ehling1,2, Eva Göb3, Stefan Bittner4
1Department of Neurology, and Institute of Physiology, Neuropathophysiology, Albert-Schweitzer-Campus 1, Westfälische Wilhelms University, 48149 Münster, Germany.
Background:
Brain ischemia is known to include neuronal cell death and persisting neurological deficits. A lack of oxygen and glucose are considered to be key mediators of ischemic neurodegeneration while the exact mechanisms are yet unclear. In former studies the expression of two different two-pore domain potassium (K2P) channels (TASK1, TREK1) were shown to ameliorate neuronal damage due to cerebral ischemia. In neurons, TASK channels carrying hyperpolarizing K+ leak currents, and the pacemaker channel HCN2, carrying depolarizing Ih, stabilize the membrane potential by a mutual functional interaction. It is assumed that this ionic interplay between TASK and HCN2 channels enhances the resistance of neurons to insults accompanied by extracellular pH shifts.
Methods:
In C57Bl/6 (wildtype, WT), hcn2+/+ and hcn2-/- mice we used an in vivo model of cerebral ischemia (transient middle cerebral artery occlusion (tMCAO)) to depict a functional impact of HCN2 in stroke formation. Subsequent analyses comprise behavioural tests and hcn2 gene expression assays.
Results:
After 60 min of tMCAO induction in WT mice, we collected tissue samples at 6, 12, and 24 h after reperfusion. In the infarcted neocortex, hcn2 expression analyses revealed a nominal peak of hcn2 expression 6 h after reperfusion with a tendency towards lower expression levels with longer reperfusion times. Hcn2 gene expression levels in infarcted basal ganglia did not change after 6 h and 12 h. Only at 24 h after reperfusion, hcn2 expression significantly decreases by ~55%. However, 30 min of tMCAO in hcn2-/- as well as hcn2+/+ littermates induced similar infarct volumes. Behavioural tests for global neurological function (Bederson score) and motor function/coordination (grip test) were performed at day 1 after surgery. Again, we found no differences between the groups.
Conclusions:
Here, we hypothesized that the absence of HCN2, an important functional counter player of TASK channels, affects neuronal survival during stroke-induced tissue damage. However, together with a former study on TASK3 these results implicate that both TASK3 and HCN2 which were supposed to be neuroprotective due to their pH-dependency, do not influence ischemic neurodegeneration during stroke in the tMCAO model.
Insights
The study investigated the role of HCN2 channels in brain ischemia, finding that their absence did not alter stroke-induced brain damage or neurological deficits in mice. These findings suggest HCN2 does not influence neurodegeneration in this stroke model.
Area of Science:
- Neuroscience
- Molecular Biology
- Cardiovascular Research
Background:
- Brain ischemia causes neuronal cell death and neurological deficits, with oxygen and glucose deprivation as key mediators.
- Two-pore domain potassium (K2P) channels like TASK1 and TREK1 have shown neuroprotective effects in cerebral ischemia.
- Neurons utilize TASK channels and the HCN2 channel in a functional interplay to stabilize membrane potential, potentially enhancing resistance to pH shifts.
Purpose of the Study:
- To investigate the functional impact of the HCN2 channel in stroke formation using a mouse model.
- To determine if the absence of HCN2 affects neuronal survival and tissue damage during cerebral ischemia.
- To explore the role of the TASK-HCN2 channel interplay in neuroprotection against ischemic insults.
Main Methods:
- Transient middle cerebral artery occlusion (tMCAO) was performed in wildtype, hcn2+/+, and hcn2-/- mice.
- Infarct volumes were measured, and behavioral tests (Bederson score, grip test) assessed neurological and motor function.
- Hcn2 gene expression levels were analyzed in infarcted neocortex and basal ganglia at various reperfusion times.
Main Results:
- Hcn2 expression peaked 6 hours after reperfusion in the neocortex, decreasing significantly by 24 hours, with no significant change in basal ganglia at earlier time points.
- Transient middle cerebral artery occlusion induced similar infarct volumes in both hcn2-/- and hcn2+/+ mice.
- No significant differences in global neurological function or motor coordination were observed between hcn2-/- and hcn2+/+ mice post-stroke.
Conclusions:
- The absence of HCN2, a functional partner of TASK channels, did not influence neuronal survival or tissue damage in the transient middle cerebral artery occlusion model.
- Contrary to the hypothesis, HCN2, like TASK3, does not appear to play a neuroprotective role in ischemic neurodegeneration within this specific stroke model.
- These findings challenge the presumed neuroprotective role of pH-dependent ion channels like TASK3 and HCN2 in the context of ischemic stroke.
