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Low expression of Kv7/M channels facilitates intrinsic and network bursting in the developing rat hippocampus
Author(s) -
Safiulina Victoria F.,
Zacchi Paola,
Taglialatela Maurizio,
Yaari Yoel,
Cherubini Enrico
Publication year - 2008
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2008.156257
Subject(s) - bursting , depolarization , neuroscience , hippocampal formation , excitatory postsynaptic potential , hippocampus , gabaergic , biology , interneuron , chemistry , biophysics , inhibitory postsynaptic potential
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; I m ), 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 I m 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.