Background and purpose: Ischemic stroke induces spreading depression of brain waves and ischemic depolarizations, suggesting electrical activity of neurons is sensitive to stroke. The present study was designed to measure the electrophysiological response of an array of individual neurons to ischemic stroke in rats.
Methods: A custom-made microwire electrode array (16 channels) was implanted in the cortical area supplied by the middle cerebral artery, spanning the core and boundary of the ischemic lesion. The electrophysiological activity of individual neurons was simultaneously recorded before, during and one week after middle cerebral artery occlusion (MCAo).
Results: Neuronal activities were significantly reduced immediately after MCAo. Intermittent silent periods (SP) appeared within minutes or hours after MCAo and lasted variable times. Between intermittent SP, neurons fired irregular bursting spikes (BS) with small magnitudes. Intermittent SP and irregular BS progressed in one day post stroke to persistent SP in channels close to the ischemic core or to regular BS with small amplitudes in the penumbral zone. Both persistent SP and regular BS persisted for at least seven days.
Conclusions: Electrode array can be used to simultaneously record multiple individual neurons in response to ischemic stroke. This study provides the first evidence that the primary electrophysiological activity of multiple individual neurons to ischemic stroke is reduced in the lesion boundary and/or stopped in and adjacent to the lesion core.