Determinants of Optogenetic Cortical Spreading Depolarizations

Area of Science:

• Neuroscience
• Optogenetics
• Migraine Research
• Brain Injury Studies

Background:

• Cortical spreading depolarization (SD) is implicated in migraine aura and secondary brain injury.
• Current experimental models for SD are invasive and can cause primary tissue damage, limiting their clinical relevance.
• A need exists for non-invasive, translatable models to study SD.

Purpose of the Study:

• To develop and validate a non-invasive method for triggering cortical spreading depolarization (SD).
• To utilize optogenetics for controlled induction of SD in a preclinical setting.
• To investigate factors influencing SD susceptibility using the novel optogenetic model.

Main Methods:

• Utilized transgenic mice (Thy1-ChR2-YFP) expressing channelrhodopsin-2 in neurons.
• Employed focal light illumination (470 nm) through the intact skull to induce depolarization.
• Measured extracellular potential shifts and [K+] changes, and administered NMDA receptor antagonist MK-801.

Main Results:

• Light-induced depolarization successfully triggered SD in a power-dependent manner above a threshold.
• Homozygous ChR2 mice exhibited higher SD susceptibility (lower light thresholds) than heterozygous mice.
• SD susceptibility varied across cortical regions, correlating with channelrhodopsin-2 expression levels; MK-801 blocked SD transition.

Conclusions:

• The optogenetic SD model provides a non-invasive and highly suitable platform for SD research.
• This model enables the examination of physiological and pharmacological modulation of SD in various study designs.
• Findings highlight the potential for optogenetics in advancing migraine and brain injury research.