Local circuit allowing hypothalamic control of hippocampal area CA2 activity and consequences for CA1

  • Vincent Robert
    INSERM UMR1266, Institute of Psychiatry and Neuroscience of Paris, Team Synaptic Plasticity and Neural Networks, Université de Paris, Paris, France
  • Ludivine Therreau
    INSERM UMR1266, Institute of Psychiatry and Neuroscience of Paris, Team Synaptic Plasticity and Neural Networks, Université de Paris, Paris, France
  • Vivien Chevaleyre
    INSERM UMR1266, Institute of Psychiatry and Neuroscience of Paris, Team Synaptic Plasticity and Neural Networks, Université de Paris, Paris, France
  • Eude Lepicard
    INSERM UMR1266, Institute of Psychiatry and Neuroscience of Paris, Team Synaptic Plasticity and Neural Networks, Université de Paris, Paris, France
  • Cécile Viollet
    INSERM UMR1266, Institute of Psychiatry and Neuroscience of Paris, Team Synaptic Plasticity and Neural Networks, Université de Paris, Paris, France
  • Julie Cognet
    INSERM UMR1266, Institute of Psychiatry and Neuroscience of Paris, Team Synaptic Plasticity and Neural Networks, Université de Paris, Paris, France
  • Arthur JY Huang
    Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
  • Roman Boehringer
    Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
  • Denis Polygalov
    Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
  • Thomas J McHugh
    Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
  • Rebecca Ann Piskorowski
    INSERM UMR1266, Institute of Psychiatry and Neuroscience of Paris, Team Synaptic Plasticity and Neural Networks, Université de Paris, Paris, France

Abstract

<jats:p>The hippocampus is critical for memory formation. The hypothalamic supramammillary nucleus (SuM) sends long-range projections to hippocampal area CA2. While the SuM-CA2 connection is critical for social memory, how this input acts on the local circuit is unknown. Using transgenic mice, we found that SuM axon stimulation elicited mixed excitatory and inhibitory responses in area CA2 pyramidal neurons (PNs). Parvalbumin-expressing basket cells were largely responsible for the feedforward inhibitory drive of SuM over area CA2. Inhibition recruited by the SuM input onto CA2 PNs increased the precision of action potential firing both in conditions of low and high cholinergic tone. Furthermore, SuM stimulation in area CA2 modulated CA1 activity, indicating that synchronized CA2 output drives a pulsed inhibition in area CA1. Hence, the network revealed here lays basis for understanding how SuM activity directly acts on the local hippocampal circuit to allow social memory encoding.</jats:p>

Journal

  • eLife

    eLife 10 e63352-, 2021-05-18

    eLife Sciences Publications, Ltd

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