title: Local Optogenetic Induction of Fast (20-40 Hz) Pyramidal-Interneuron Network Oscillations in the In Vitro and In Vivo CA1 Hippocampus: Modulation by CRF and Enforcement of Perirhinal Theta Activity.
abstract: The neurophysiological processes that can cause theta-to-gamma frequency range (4-80 Hz) network oscillations in the rhinal cortical-hippocampal system and the potential connectivity-based interactions of such forebrain rhythms are a topic of intensive investigation. Here, using selective Channelrhodopsin-2 (ChR2) expression in mouse forebrain glutamatergic cells, we were able to locally, temporally precisely, and reliably induce fast (20-40 Hz) field potential oscillations in hippocampal area CA1 in vitro (at 25°C) and in vivo (i.e., slightly anesthetized NEX-Cre-ChR2 mice). As revealed by pharmacological analyses and patch-clamp recordings from pyramidal cells and GABAergic interneurons in vitro, these light-triggered oscillations can exclusively arise from sustained suprathreshold depolarization (~200 ms or longer) and feedback inhibition of CA1 pyramidal neurons, as being mandatory for prototypic pyramidal-interneuron network (P-I) oscillations. Consistently, the oscillations comprised rhythmically occurring population spikes (generated by pyramidal cells) and their frequency increased with increasing spectral power. We further demonstrate that the optogenetically driven CA1 oscillations, which remain stable over repeated evocations, are impaired by the stress hormone corticotropin-releasing factor (CRF, 125 nM) in vitro and, even more remarkably, found that they are accompanied by concurrent states of enforced theta activity in the memory-associated perirhinal cortex (PrC) in vivo. The latter phenomenon most likely derives from neurotransmission via a known, but poorly studied excitatory CA1→PrC pathway. Collectively, our data provide evidence for the existence of a prototypic (CRF-sensitive) P-I gamma rhythm generator in area CA1 and suggest that CA1 P-I oscillations can rapidly up-regulate theta activity strength in hippocampus-innervated rhinal networks, at least in the PrC.
authors.affiliation: Max Planck Institute of PsychiatryMunich, Germany; Department "Stress Neurobiology and Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of PsychiatryMunich, Germany.
authors.forename: Julien
authors.initials: J
authors.lastname: Dine
authors.affiliation: Max Planck Institute of PsychiatryMunich, Germany; Department "Stress Neurobiology and Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany; Research Group "Neuronal Plasticity", Max Planck Institute of PsychiatryMunich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Genewsky
authors.affiliation: Max Planck Institute of PsychiatryMunich, Germany; Department "Stress Neurobiology and Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of PsychiatryMunich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Hladky
authors.affiliation: Max Planck Institute of PsychiatryMunich, Germany; Department "Stress Neurobiology and Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany; Research Group "Neuronal Plasticity", Max Planck Institute of PsychiatryMunich, Germany.
authors.forename: Carsten T
authors.initials: CT
authors.lastname: Wotjak
authors.affiliation: Max Planck Institute of PsychiatryMunich, Germany; Department "Stress Neurobiology and Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany; Research Group "Molecular Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany.
authors.forename: Jan M
authors.initials: JM
authors.lastname: Deussing
authors.affiliation: Max Planck Institute of Psychiatry Munich, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Zieglgänsberger
authors.affiliation: Max Planck Institute of PsychiatryMunich, Germany; Department "Stress Neurobiology and Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany; The Ruhman Family Laboratory for Research on the Neurobiology of Stress, Department of Neurobiology, Weizmann Institute of ScienceRehovot, Israel.
authors.forename: Alon
authors.initials: A
authors.lastname: Chen
authors.affiliation: Max Planck Institute of PsychiatryMunich, Germany; Department "Stress Neurobiology and Neurogenetics", Max Planck Institute of PsychiatryMunich, Germany; Scientific Core Unit "Electrophysiology and Neuronal Network Dynamics", Max Planck Institute of PsychiatryMunich, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Eder
keywords: CA1; CRF; gamma; hippocampus; optogenetics; perirhinal cortex; pyramidal-interneuron network oscillations; theta