Mislocalization of h channel subunits underlies h channelopathy in temporal lobe epilepsy

Many animal models of temporal lobe epilepsy (TLE) begin with status epilepticus (SE) followed by a latency period. Increased hippocampal pyramidal neuron excitability may contribute to seizures in TLE. I(h), mediated by h channels, regulates intrinsic membrane excitability by modulating synaptic integration and dampening dendritic calcium signaling. In a rat model of TLE, we found bidirectional changes in h channel function in CA1 pyramidal neurons. 1-2 d after SE, before onset of spontaneous seizures, physiological parameters dependent upon h channels were augmented and h channel subunit surface expression was increased. 28-after 30 d following SE, onset of spontaneous seizures, h channel function in dendrites was reduced, coupled with diminished h channel subunit surface expression and relocalization Of Subunits from distal dendrites to soma. These results implicate h channel localization as a molecular mechanism influencing CA1 excitability in TLE. (C) 2008 Elsevier Inc. All rights reserved.