Role of Somatostatin-Positive Cortical Interneurons in the Generation of Sleep Slow Waves

Chadd M Funk, Kayla Peelman, Michele Bellesi, William Marshall, Chiara Cirelli, Giulio Tononi

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

During non-rapid eye-movement (NREM) sleep, cortical and thalamic neurons oscillate every second or so between ON periods, characterized by membrane depolarization and wake-like tonic firing, and OFF periods, characterized by membrane hyperpolarization and neuronal silence. Cortical slow waves, the hallmark of NREM sleep, reflect near-synchronous OFF periods in cortical neurons. However, the mechanisms triggering such OFF periods are unclear, as there is little evidence for somatic inhibition. We studied cortical inhibitory interneurons that express somatostatin (SOM), because ∼70% of them are Martinotti cells that target diffusely layer I and can block excitatory transmission presynaptically, at glutamatergic terminals, and postsynaptically, at apical dendrites, without inhibiting the soma. In freely moving male mice, we show that SOM+ cells can fire immediately before slow waves and their optogenetic stimulation during ON periods of NREM sleep triggers long OFF periods. Next, we show that chemogenetic activation of SOM+ cells increases slow-wave activity (SWA), slope of individual slow waves, and NREM sleep duration; whereas their chemogenetic inhibition decreases SWA and slow-wave incidence without changing time spent in NREM sleep. By contrast, activation of parvalbumin+ (PV+) cells, the most numerous population of cortical inhibitory neurons, greatly decreases SWA and cortical firing, triggers short OFF periods in NREM sleep, and increases NREM sleep duration. Thus SOM+ cells, but not PV+ cells, are involved in the generation of sleep slow waves. Whether Martinotti cells are solely responsible for this effect, or are complemented by other classes of inhibitory neurons, remains to be investigated.SIGNIFICANCE STATEMENT Cortical slow waves are a defining feature of non-rapid eye-movement (NREM) sleep and are thought to be important for many of its restorative benefits. Yet, the mechanism by which cortical neurons abruptly and synchronously cease firing, the neuronal basis of the slow wave, remains unknown. Using chemogenetic and optogenetic approaches, we provide the first evidence that links a specific class of inhibitory interneurons-somatostatin-positive cells-to the generation of slow waves during NREM sleep in freely moving mice.

Original languageEnglish
Pages (from-to)9132-9148
Number of pages17
JournalJournal of Neuroscience
Volume37
Issue number38
Early online date20 Sep 2017
DOIs
Publication statusPublished - 20 Sep 2017

Bibliographical note

Copyright © 2017 the authors 0270-6474/17/379132-17$15.00/0.

Keywords

  • Animals
  • Brain Waves/physiology
  • Cerebral Cortex/physiology
  • Cortical Synchronization/physiology
  • Interneurons/physiology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Nerve Net/physiology
  • Neural Inhibition/physiology
  • Sleep, REM/physiology
  • Somatostatin/metabolism

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