Study examined the relationship between the ambient temperature and quality of sleep

The findings reveal the science behind springtime lethargy.

Ambient temperatures—the temperature of the environment that surrounds you—can have a significant effect on how much and how well you sleep.

A new study by UNIST, that focuses on the association between ambient temperature and quality of sleep has revealed the principle behind the changing sleep patterns, according to the ambient temperature.

The study uses Drosophila as a model of sleep to understand how genes, neurotransmitters, and neural activity collectively regulate sleep behaviors. 

Drosophila, a fruit fly, is less active during the day in hot environments and does not sleep well at night. To find out the principle behind this mechanism, scientists cultured the genetically engineered fruit flies under temperature, similar to hot summer days, and observed their sleep patterns.

The fruit flies used in the experiment have the mutation in the ‘Shaker (Sh)’ gene. The protein produced by this gene creates a pathway through which potassium ions (K⁺) pass in the brain. If this protein is deficient, it activates nerve cells excessively to suppress sleep. After all, mutant fruit flies sleep less than other fruit flies.

However, even when the same type of fruit fly was cultured in hot environments, sleep suppression did not appear. The study noted that this phenomenon is due to the disappearance of the link between dFSB (dorsal Fan-Shaped Body neuron) and the inhibitory neurotransmitter GABA.

The Shaker (Sh)-expressing GABAergic neurons, projecting onto the dorsal fan-shaped body (dFSB) found to regulate temperature-adaptive sleep behaviors in Drosophila. Loss of Sh function suppressed sleep at low temperature, whereas light and high temperature cooperatively gated Sh effects on sleep. Sh depletion in GABAergic neurons partially phenocopied Sh mutants.

Scientists found that the neuronal junction (synapses) between sleep-regulating neurons that sends and receives signals using GABA (Gamma-Amino Butyric Acid), the major inhibitory neurotransmitter in the brain, disappears when the temperature rises, and thus changes the sleep pattern.

Professor Chunghun Lim in the School of Life Sciences at UNIST said“Our study establishes a genetic pathway that constitutes temperature-sensitive GABA transmission to the sleep-promoting neural locus and generates neural plasticity underpinning the adaptive organization of sleep architecture. Knowing the changes in sleep patterns, caused by springtime lethargy and heatwaves, will help us better resolve—or help treat—sleep disorders.”

This work has been supported by grants from the Suh Kyungbae Foundation, as well as the Advanced Research Center Program from the National Research Foundation (NRF) funded by the Ministry of Science and ICT (MSIT). The Global Ph.D. Fellowship project has also supported it.

Journal Reference:
  1. The voltage-gated potassium channel Shaker promotes sleep via thermosensitive GABA transmission. DOI: 10.1038/s42003-020-0902-8

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