title: Depolarizing GABA acts on intrinsically bursting pyramidal neurons to drive giant depolarizing potentials in the immature hippocampus.
abstract: Spontaneous periodic network events are a characteristic feature of developing neuronal networks, and they are thought to play a crucial role in the maturation of neuronal circuits. In the immature hippocampus, these types of events are seen in intracellular recordings as giant depolarizing potentials (GDPs) during the stage of neuronal development when GABA(A)-mediated transmission is depolarizing. However, the precise mechanism how GABAergic transmission promotes GDP occurrence is not known. Using whole-cell, cell-attached, perforated-patch, and field-potential recordings in hippocampal slices, we demonstrate here that CA3 pyramidal neurons in the newborn rat generate intrinsic bursts when depolarized. Furthermore, the characteristic rhythmicity of GDP generation is not based on a temporally patterned output of the GABAergic interneuronal network. However, GABAergic depolarization plays a key role in promoting voltage-dependent, intrinsic pyramidal bursting activity. The present data indicate that glutamatergic CA3 neurons have an instructive, pacemaker role in the generation of GDPs, whereas both synaptic and tonic depolarizing GABAergic mechanisms exert a temporally nonpatterned, facilitatory action in the generation of these network events.
authors.affiliation: Department of Biological and Environmental Sciences, University of Helsinki, FIN-00014 Helsinki, Finland.
authors.forename: Sampsa T
authors.initials: ST
authors.lastname: Sipilä
authors.forename: Kristiina
authors.initials: K
authors.lastname: Huttu
authors.forename: Ivan
authors.initials: I
authors.lastname: Soltesz
authors.forename: Juha
authors.initials: J
authors.lastname: Voipio
authors.forename: Kai
authors.initials: K
authors.lastname: Kaila
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D058787:GABA-A Receptor Antagonists; D006624:Hippocampus / Q000254:growth & development / Q000502:physiology*; D066298:In Vitro Techniques; D007395:Interneurons / Q000502:physiology; D008564:Membrane Potentials; D009415:Nerve Net / Q000502:physiology; D018408:Patch-Clamp Techniques; D010507:Periodicity; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid