Kv4.2 block of long-term potentiation is partially dependent on synaptic NMDA receptor remodeling

Proper expression of synaptic NMDA receptors (NMDARs) is necessary to regulate synaptic Ca²⁺ influx and the induction the long-term potentiation (LTP) in the mammalian hippocampus. Previously we reported that expressing the A-type K⁺ channel subunit Kv4.2 in CA1 neurons of organotypic slice cultures reduced synaptic NR2B-containing NMDAR expression and completely blocked LTP induced by a pairing protocol. As pretreatment with an NMDAR antagonist (APV) overnight blocked the reduction of NR2B-containing receptors in neurons expressing EGFP-labeled Kv4.2 (Kv4.2g), we hypothesized that LTP would be rescued in Kv4.2g neurons by overnight treatment with APV. We report here that the overnight APV pretreatment in Kv4.2g-expressing neurons only partially restored potentiation. This partial potentiation was completely blocked by inhibition of the CAMKII kinase. These results indicate that A-type K⁺ channels must regulate synaptic integration and plasticity through another mechanism in addition to their regulation of synaptic NR2 subunit composition. We suggest that dendritic excitability, which is regulated by Kv4.2 expression, also contributes to synaptic plasticity.