Abstract
GABAergic inhibition plays a critical role in the regulation of neuronal activity. In the neocortex, inhibitory interneurons that target the dendrites of pyramidal cells influence both electrical and biochemical postsynaptic signaling. Voltage-gated ion channels strongly shape dendritic excitability and the integration of excitatory inputs, but their contribution to GABAergic signaling is less well understood. Here, we examine the actions of potassium channels in regulating dendritic inhibition in mouse visual cortex. By combining 2-photon calcium imaging and focal GABA uncaging, we show that A-type channels normally suppress the GABAergic inhibition of calcium signals evoked by back-propagating action potentials in dendritic spines and shafts. Moreover, the voltage-dependent inactivation of these channels leads to enhancement of dendritic inhibition following somatic spiking. Overall, our findings highlight the interaction between intrinsic and synaptic properties and reveal a novel mechanism for the activity-dependent scaling of GABAergic inhibition.