High-Frequency Photoconductive Stimulation Reveals Central Role of Mitochondrial Permeability Transition Pore in Activity-Driven Neuronal Cell Death

Abstract

Loss of the ability to regulate calcium is a central event leading to neuronal cell death during a wide range of pathological conditions including stroke and seizure. Here we present a new dissociated hippocampal cell culture model of acute electrical activity which incorporates the photoconductive stimulation of neuronal networks grown on silicon wafers. This technology allows precise modeling of user defined neuronal activity patterns, and the study of their effect on neuronal physiology. Here, seizure-like conditions were created by continuous stimulation, causing hundreds of neurons to fire synchronously at 50 Hz for 4 minutes. This stimulation protocol induced cell death as monitored by propidium iodide staining. The number of dead cells per stimulation region increased from 3.6 ± 2.1 preceding stimulation to 81 ± 21 30 minutes following stimulation. Excitotoxicity primarily affected excitatory rather than inhibitory neurons, and was preceded by an increase in intracellular calcium as well as changes in the mitochondrial morphology and membrane potential as measured by a tetramethylrhodamine methyl ester (TMRM) assay. Cyclosporin A (CsA), a mitochondrial permeability transition pore (PTP) blocker, was effective in preventing cell death. We propose that photoconductive stimulation is a useful tool for investigating the pathogenesis of excitotoxicity in vitro.