Fruit fly.

Neuron cluster which can override sleep identified in the fruit fly brain

Certain neurons in the brains of male fruit flies will suppress the animal’s sleep if they have any female to court nearby.

Fruit fly.

Image credits John Tann / Flickr.

Who here hasn’t had to forgo the sweet embrace of sleep when something important pops up — a paper due in the morning, a book you just can’t put down. Or, if you’re a male fruit fly, because there’a a change you might get some action.

A team of researchers from the Sidney Kimmel Medical College at Thomas Jefferson University found that like humans, fruit flies (Drosophila melanogaster) can keep themselves awake if something important pops up. More specifically, they report that a certain group of neurons in the males’ brains can suppress their sleep so they can court female flies.

Up all night to get lucky

The study started from the observation that although male flies usually spend most of the night awake trying to court nearby ladies, those who have recently mated several times (and thus have a low sexual drive) tend to ignore females and simply go to sleep.

It would suggest that something in the fly’s brains has to (consciously or unconsciously) decide what was more important to the fly at one point — sex or sleep. But nobody knew exactly how this process unfolded, and that’s what the team set out to understand.

“The idea that sleep and courtship might compete with each other is intuitive but had not been studied experimentally, and the underlying neural mechanisms had not been explored. We wanted to know how the sleep drive and sex drive compete to determine behavior,” says Kyunghee Koh, PhD, Associate Professor of Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University and senior author on the study.

The team zeroed in on a bunch of neurons dubber MS1 (male specific 1) that seem to be at the root of this process. MS1 neurons aren’t part of any previously known groups of neurons which play a part in male sexual behavior, but work by keeping the males awake so they can ply their charm. They release octopamine, a neurotransmitter similar in function to noradrenalin, which will keep male flies awake in a sexual setting. Experiments showed that silencing the MS1 cluster caused males to go to sleep even if there were females around, and artificially activating the neurons kept males awake even in the absence of females.

Interestingly enough, while females have the same bunch of neurons they don’t seem to function the same — activating or inactivating the cluster had no effect on the females’ sleep.

We don’t yet know whether there are similar mechanisms functioning in our brains, but we do know that noradrenalin creates wakefulness in humans. This would suggest that the neurotransmitter plays a key role when we’re trying to consciously suppress sleep, the team notes.

But until we get a definitive answer on that, the team wants to identify which neuron communicate directly with the MS1 cluster, examine how their activation leads to sleep suppression and how MS1 neuronal activity is regulated.

The full paper “Identification of octopaminergic neurons that modulate sleep suppression by male sex drive” has been published in the journal eLife.

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