Layer-specific modulation of pyramidal cell excitability by electroconvulsive shock.

Dysregulation of cortical excitability crucially involves in behavioral and cognitive deficits of neurodegenerative and neuropsychiatric diseases. Electroconvulsive shock (ECS) changes neuronal excitability and has been used in the therapy of major depressive disorder and mood disorders. However, the action and the targets of the ECS in the cortical circuits are still poorly understood. Here we show that the ECS differently changes intrinsic properties of pyramidal cells (PCs) among superficial and deep layers. In layer 2/3 PCs, the ECS induced membrane hyperpolarization and the reduction of input resistances. In layer 5 PCs, the ECS also induced membrane hyperpolarization but had little effects on input resistances. In layer 6 PCs, the ECS had no effects on both of resting membrane potentials and input resistances. In addition, the ECS reduced the firing frequency of PCs in layer 2/3 but not in both layers 5 and 6. We further examined the ECS-induced changes in the influx of Ca2+ currents, and observed an enhanced Ca2+ currents in PCs of both layers 2/3 and 5 but not of layer 6. Thus, this study suggests the layer-specific suppression of PC excitability which will underlie the mechanism of the ECS action on the cortical activity.