Interdigitated Electrodes and Their Possibility to Determine the Excitation Region in Neurons in Cultured Networks

This report concerns investigations of the activation process of nerve cells cultured on large planar interdigitated electrodes. Cultured neurons from embryonic rat cerebral cortex form electrophysiologically active networks after one week in vitro. The treatment with antagonists to ionotropic glutamate and GABAA receptors blocks synaptic neurotransmission without affecting intrinsic excitability of neurons. Standard stimulation parameters,which were previously determined to trigger a generalized network response in control networks,were ineffective for activation of networks under a synaptic activity blockade. Here we show that in these conditions a pulse sequence of ten biphasic pulses with amplitude of ±2.2 V is adequate for global network stimulation,without cell damage. In specially designed compartment cultures we analyzed further the stimulation process in control and synaptically blocked networks with cell bodies spatially separated from the electrodes. Our results suggest that the direct stimulation of few neurons trigger network-wide responses by the activation of synaptic connections. Further,the stimulation of axonal neuritic extensions is sufficient to active single neurons.