Local targeted suppression of neocortical spreading depolarization amplitude by viral expression of KCa3.1 channels.

Cortical spreading depolarization (SD) underlies migraine, frequently co-occurs with seizures, and is associated with poor prognosis after stroke. In rodent models, most genetic therapies for epilepsy suppress seizures by enhancing neuronal K⁺ conductance. Although seizures and SD often co-occur and SD causes temporary neuronal silencing, it remains unknown whether K⁺-conductance-enhancing gene therapy affects SD. Here, we present a genetic method for targeted downregulation of SD using adeno-associated virus to express KCNN4, which encodes the Ca²⁺-gated KCa3.1 channels. We tested the effect of KCNN4 expression in rodent neocortex using patch-clamp electrophysiology, functional imaging in brain slices, and field potential recording in vivo. KCNN4 expression reduced acute seizure-like activity, lowered SD amplitude several-fold both in vivo and in vitro, and slowed SD propagation in brain slices, where epileptiform activity paradoxically reappeared faster after SD. Moreover, SD triggered a Ca²⁺ rebound upon restoration of epileptiform activity, which was counterbalanced by KCa3.1-mediated afterhyperpolarization. Targeted suppression of SD amplitude using KCNN4 expression provides a proof-of-principle for potential gene therapy models for disorders complicated by SD. Reducing SD via increased neuronal K⁺ conductance may have a side effect worth considering in gene therapy for epilepsy, as some literature suggest that SD itself may terminate seizures.