Not only did it increase dopamine release during the period of acute sleep loss, but it also improved synaptic plasticity, literally rewiring the brain to maintain a happy mood for the next few days.
The new findings, published online in the journal Neuron, could help researchers better understand how moods change naturally.
It could also lead to a more complete understanding of how fast-acting antidepressants (such as ketamine) work and help researchers identify previously unknown targets for new antidepressant drugs.
“Chronic sleep loss is well studied and its detrimental effects are widely documented,” said Professor Yevgenia Kozorovitskiy of the university.
“But brief sleep loss, such as the equivalent of a student pulling an all-nighter before an exam, is less understood.
“We found that lack of sleep induces a potent antidepressant effect and rewires the brain. This is an important reminder of how our casual activities, such as a sleepless night, can fundamentally alter the brain in just a few hours,” Kozorovitskiy added.
In the research, the team developed a new experiment to induce acute sleep loss in mice that did not have genetic predispositions related to human mood disorders.
The experimental setup needed to be gentle enough to avoid causing substantial stress to the animals, but uncomfortable enough to prevent the animals from falling asleep.
After a sleepless night, the animals’ behavior changed and they became more aggressive, hyperactive and hypersexual, compared to controls who experienced a typical night’s sleep.
Using optical and genetically encoded tools, the researchers measured the activity of dopamine neurons, which are responsible for the brain’s reward response. And they found that activity was greater in the animals during the brief period of sleep loss.
While researchers don’t fully understand why lack of sleep causes this effect on the brain, Kozorovitskiy suspects that evolution is at play.
Kozorovitskiy also warns people not to start staying up all night to lighten their mood.
“The antidepressant effect is temporary and we know the importance of getting a good night’s sleep,” he said.
“I would say it’s better to go to the gym or take a nice walk. This new knowledge is more important when it comes to matching a person with the right antidepressant.”