London, Jul 30 (IANS): Researchers have identified a brain chemical absence of which can lead to hyperactivity and sleeplessness.

In the experiments, mice without the GABA (gamma-aminobutyric acid) chemical developed characteristics similar to a medical condition called mania, in which patients experience restlessness and sleeplessness, the study noted.

This discovery could help researchers to develop new drugs that promote better sleep, or control hyperactivity in people with the medical condition mania.

"Sleep is essential for health. We have to do it every day. But nobody yet knows why," said one of the lead researchers Bill Wisden, professor at Imperial College London.

The chemicals they studied, histamine and GABA, are produced in a primitive part of the brain that is highly similar in mice and humans.

The researchers found that GABA and histamine are made in the same brain cells, called histamine neurons.

They altered the levels of the GABA produced by the mice's brains and measured what changes this had on their brain activity over the day and night.

The scientists found that compared with normal mice, those without GABA ran twice as far and twice as fast, and maintained or even increased their overall activity over a 30 minute period.

"What particularly surprised us was how little the mice were affected by sleep deprivation," Nick Franks, professor at Imperial College London, pointed out.

The findings were detailed in the journal Neuron.