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Tetanic stimulation of Schaffer collaterals induces rhythmic bursts via NMDA receptor activation in rat CA1 pyramidal neurons
Author(s) -
Bonansco Christian,
González de la Vega Alberto,
González Alegre Pedro,
Borde Michel,
GarcíaSegura Luis M.,
Buño Washington
Publication year - 2002
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/hipo.10023
Subject(s) - neuroscience , nmda receptor , tetanic stimulation , stimulation , cnqx , ampa receptor , depolarization , glutamate receptor , hippocampal formation , bursting , chemistry , picrotoxin , pyramidal cell , tetrodotoxin , apical dendrite , hippocampus , biology , biophysics , receptor , gabaa receptor , inhibitory postsynaptic potential , excitatory postsynaptic potential , cerebral cortex , biochemistry
Exploring the principles that regulate rhythmic membrane potential (V m ) oscillations and bursts in hippocampal CA1 pyramidal neurons is essential to understanding the θ rhythm (θ). Recordings were performed in vitro in hippocampal slices from young rats, and a group of the recorded CA1 pyramidal cells were dye‐filled with carboxifluorescein and immunolabeled for the R1 subunit of the NMDA receptor. Tetanic stimulation of Schaffer collaterals (SCs) and iontophoresis of glutamate evoked rhythmic V m oscillations and bursts (≈10 mV, ≈7 Hz, 2–5 spikes per burst) in cells (31%) placed close to the midline (“medial cells”). Rhythmic bursts remained under picrotoxin (10 μM) and V m oscillations persisted with tetrodotoxin (1.5 μM), but bursts were blocked by AP5 (25 μM) and Mg 2+ ‐free solutions. Depolarization and AMPA never induced rhythmic bursts. The rest of the neurons (69%), recorded closer to the CA3 region (“lateral cells”), discharged rhythmically single repetitive spikes under SC stimulation and glutamate in control conditions, but fired rhythmic bursts under similar stimulation, both when NMDA was applied and when non‐NMDA receptors were blocked with CNQX (20 μM). Medial cells exhibited a larger NMDA current component and a higher NMDAR1 density at the apical dendritic shafts than lateral cells, suggesting that these differences underlie the dissimilar responses of both cell groups. We conclude that the “θ‐like” rhythmic oscillations and bursts induced by glutamate and SC stimulation relied on the activation of NMDA receptors at the apical dendrites of medial cells. These results suggest a role of CA3 pyramidal neurons in the generation of CA1 θ via the activation of NMDA receptors of CA1 pyramidal neurons. Hippocampus 2002;12:434–446. © 2002 Wiley‐Liss, Inc.