Inherited channelopathies are at the origin of many neurological disorders. Here we report a form of channelopathy that is acquired in experimental temporal lobe epilepsy (TLE), the most common form of epilepsy in adults. The excitability of CA1 pyramidal neuron dendrites was increased in TLE because of decreased availability of A-type potassium ion channels due to transcriptional (loss of channels) and posttranslational (increased channel phosphorylation by extracellular signal-regulated kinase) mechanisms. Kinase inhibition partly reversed dendritic excitability to control levels. Such acquired channelopathy is likely to amplify neuronal activity and may contribute to the initiation and/or propagation of seizures in TLE.