Study shows microglia involved in sleep regulation, and possibly sleep disorders, in females

Sleep is essential to maintain physical and mental health, but sleep disorders can keep many people – especially women – from getting the rest they need.

In her recent first-author paper published in Brain, Behavior, and Immunity, PhD student Katherine Picard (Tremblay Lab) and her collaborators from the Université de Bordeaux and Sapienza Università di Roma explore if microglia play a role in female sleep regulation given this higher prevalence of various sleep disorders in women.

L - R: Katherine Picard and Dr. Marie-Ève Tremblay

Microglia, the brain’s resident immune cells, are required for brain health. Katherine and the team found that, in the absence of microglia, female subjects spent more time in non-rapid eye movement (NREM) sleep, the first stage of the sleep cycle that is critical for strengthening immunity and consolidating memory. The subjects also had an increased number of NREM sleep episodes. Katherine says this increase could indicate sleep fragmentation, which is present in some sleep disorders, including sleep apnea and periodic limb movement disorder. When microglia returned, the number of NREM sleep episodes lowered but still remained higher than pre-depletion levels.

The researchers also observed changes in neuronal activity in the primary motor cortex, a region involved in the regulation of sleep, along the light–dark cycle. (The light–dark cycle of a person’s environment help regulate their sleep–wake cycle.) The study found that the depletion of microglia increased neuronal activity during both the light (awake) and dark (sleep) phases. Specifically, the depletion increased the amplitude of excitatory post-synaptic currents during the light phase and increased the frequency of these currents in both light and dark phases. “It is very hypothetical at this point, but this could mean that the reorganization of synapses that normally happens during sleep – which allows for memory consolidation, among other things – is not happening as it should,” says Katherine. “Long-term, this could maybe lead to cognitive deficits.”

“These results indicate that microglia are involved in the sleep regulation of females, potentially through the regulation of neuronal activity,” she explains. The findings also indicate that microglia could potentially play a role in the development and/or progression of sleep disorders.

Previous studies, which focused solely on male subjects, show microglia have several other functions throughout the sleep-wake cycle, including playing a role in sleep promotion.