Low expression of Kv7/M channels facilitates intrinsic and network bursting in the developing rat hippocampus

Victoria F. Safiulina, Paola Zacchi, Maurizio Taglialatela, Yoel Yaari, Enrico Cherubini*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

Early in development, network activity in the hippocampus is characterized by recurrent synchronous bursts, whose cellular correlates are giant depolarizing potentials (GDPs). The propensity for generating GDPs is attributed to GABAergic synaptic transmission being depolarizing and excitatory in neonatal neurons. However, developmental regulation of intrinsic conductances may also influence GDPs generation. A likely candidate is the non-inactivating, low-threshold, muscarinic-sensitive K+ current (M current; Im), which down-regulates intrinsic bursting activity in adult hippocampal pyramidal neurons. Western blot analysis of homogenates of the CA3 hippocampal region showed that expression of the Kv7.2 subunit, one of the constituents of neuronal M channels, is weak in neonatal neurons, and markedly increases after the first postnatal week. Likewise, the density of Im was very low in neonatal CA3 pyramidal cells and increased later on. Spontaneously occurring intrinsic bursts in neonatal neurons were longer and more robust, and recurred more regularly, than in juvenile neurons. The I m blocker linopirdine only mildly affected intrinsic bursting in neonatal neurons, but strongly facilitated and regularized it in juvenile neurons. We conclude that the low expression of Kv7/M channels and the depolarizing action of GABA early after birth enhance intrinsic bursting and neuronal synchronization leading to generation of GDPs within the hippocampal network.

Original languageEnglish
Pages (from-to)5437-5453
Number of pages17
JournalJournal of Physiology
Volume586
Issue number22
DOIs
StatePublished - 15 Nov 2008

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