DALLAS, April 21 (UPI) -- U.S. researchers said by tracking which nerve cells in mouse brains stimulate others, they found how a type of neuron is responsible for sleep and waking.
Researchers at the University of Texas Southwestern Medical Center used genetically engineering mice to produce a tracer protein only in a certain population of neurons. The tracer transfers itself from one neuron to another "upstream" into the brain, so the researchers could track the tracer to map the neuron connections.
The team focused on neurons that produce a protein called orexin that helps keep animals awake. In humans, a deficiency in orexin causes narcolepsy, a rare disease in which people fall asleep uncontrollably. Victims also experience excessive daytime sleepiness and a sudden muscle weakness called cataplexy.
The experiments have revealed how brains receive signals from neurons active only during sleep, as well as signals from the nerve cells that are very active during wakefulness.
The researchers said because orexin-producing neurons play such a key role in regulating sleep, determining how they connect to other neurons is an important step toward understanding how and why people sleep.
