Sleep is a universal phenomenon in the animal kingdom. On the one hand has a restorative function, allowing the recovery of energy expended during wakefulness and the removal of waste products, on the other hand plays a fundamental role in cognitive processes and information processing. During sleep, computational processes such as the formation and consolidation of memory related to events that occurred during wakefulness and sleep alteration or deprivation can lead to cognitive disorders.

Although it has been shown that the sleep-wake cycle is regulated both by internal stimuli (main biological clock, located in the suprachiasmatic nucleus of the hypothalamus) and by external stimuli (such as the dark-light cycle, work activity or meals), the cellular mechanisms underlying the sleep-wake cycle are still partly unknown.

This research area includes a new study coordinated by researchers from the Department of Physiology and Pharmacology "Vittorio Erspamer" of Sapienza University of Rome, in collaboration with Sapienza's Department of Molecular Medicine, the National Research Council and other universities and international research centres, in which the role of microglia cells in regulating the sleep-wake cycle is demonstrated for the first time.

These cells are involved in active immune defence in the central nervous system, and, according to work published in the journal Glia, they also help regulate sleep duration through their interaction with nerve cells.

"Microglia," says Cristina Limatola of Sapienza, study coordinator, "regulate the duration of the sleep phase in mice also through the chemokine receptor CX3CR1, which is highly expressed in these cells where it plays important roles during the development and maturation of the central nervous system."

"Animal models in which microglia have been eliminated through treatment with a CSF1R receptor antagonist, or lacking the CX3CR1 receptor on microglia," adds Limatola, "show an increase in the non-rapid eye movement (NREM) phase of sleep during waking hours associated with alterations in synaptic transmission at the level of the hippocampus, a region that is crucial for the formation of long-term memory."

This work helps to unravel the mechanisms underlying the sleep-wake cycle regulation and opens up new perspectives on the role of glial cells in brain functioning.

References: 

Microglia modulate hippocampal synaptic transmission and sleep duration along the light/dark cycle - Giorgio Corsi, Katherine Picard, Maria Amalia di Castro, Stefano Garofalo, Federico Tucci, Giuseppina Chece, Claudio del Percio, Maria Teresa Golia, Marcello Raspa, Ferdinando Scavizzi, Fanny Decoeur, Clotilde Lauro, Mara Rigamonti, Fabio Iannello, Davide Antonio Ragozzino, Eleonora Russo, Giovanni Bernardini, Agnès Nadjar, Maria Eve Tremblay, Claudio Babiloni, Laura Maggi, Cristina Limatola - Glia 2021 Sep 6 DOI: 10.1002/glia.24090

Further Information 

Cristina Limatola
Department of Physiology and Pharmacology "Vittorio Erspamer"
cristina.limatola@uniroma1.it