A Photothrombotic Cortical Stroke Mouse Model Produces the Spike Ripple Epileptic Biomarker
Abstract number :
1.098
Submission category :
2. Translational Research / 2C. Biomarkers
Year :
2023
Submission ID :
396
Source :
www.aesnet.org
Presentation date :
12/2/2023 12:00:00 AM
Published date :
Authors :
Presenting Author: Dana Shaw, BS – Boston University
Krishnakanth Kondabolu, PhD – Boston University; Katherine Walsh, BS – MGH/Harvard; Wen Shi, PhD – MGH/Harvard; Enrico Rillosi, BS – Boston University; Maxine Hsiung, Undergraduate – Boston University; Uri Eden, PhD – Boston University; Robert Richardson, MD, PhD – MGH/Harvard; Mark Kramer, PhD – Boston University; Catherine Chu, MD – MGH/Harvard; Xue Han, PhD – Boston University
Rationale: Interictal epileptiform discharges (spikes), high-frequency oscillations (such as 80-250Hz ripples), and spike ripples (SR, the co-occurrence of spikes and ripples) are each well-established epileptic biomarkers. Theories suggest spikes emerge from an imbalance between excitatory and inhibitory activity. Pathological ripples are thought to result from fast-spiking interneuron activity or communication between excitatory neurons via gap junctions. However, direct experimental testing of their mechanisms has been limited due to a lack of animal models. Here, we developed a cortical photothrombotic stroke mouse model expressing these epileptic biomarkers that allows for high-speed cellular membrane voltage imaging of specific neuronal cell types at single-cell resolution. Using this model, one can analyze both action potentials and subthreshold membrane voltage dynamics of different neurons during SRs to probe underlying cellular and network mechanisms of these pathological electrographic elements.
Methods: Unilateral strokes were induced in primary motor cortex (M1) of C57BL6 mice (N=7) using a cortical photothrombotic procedure. Briefly, Rose Bengal (light-absorbing dye) was injected retro-orbitally or intraperitoneally and cold white light was directed through the skull over M1 for ten minutes. One week after stroke, intracranial electrodes were implanted in M1 bilaterally (one adjacent to the stroke and another in the contralateral M1). For referencing, each mouse had an additional pair of electrodes either in M1 anterior to the stroke, or in striatum, or in thalamus. Local field potentials (LFPs) were collected over many weeks while mice were head-fixed and voluntarily locomoting on a spherical treadmill. Data was visually inspected to remove periods containing motion artifacts. Delta power was computed and SRs were automatically detected using a previously developed detector (Chu et al, 2017). SR detections from one recording session from each mouse were additionally classified by a blinded human expert. At the end of the recording, immunohistochemistry was performed to confirmed unilateral M1 strokes.
Results: There was a significant increase in cortical delta power (one-four Hz) in the stroke hemisphere compared to the non-stroke hemisphere (p< 0.001 for all mice, nonparametric bootstrap). The automatically detected SR rate in M1 was increased in the stroke hemisphere compared to the non-stroke hemisphere across all mice (Wilcoxon signed rank test, p< 0.05 for 6 mice and p=0.063 for 1 mouse). Expert-classified SRs confirmed this observation (p< 0.05, Wilcoxon signed rank test). Furthermore, all detections in the non-stroke hemisphere were classified as false positives by the expert, highlighting the spatial specificity of the SR biomarker in our model.
Translational Research