A commonly-prescribed antidepressant increases the lifespan of worms to the human equivalent of a centenarian, scientists looking for chemicals that prolong longevity reported Wednesday.

What determines lifespan remains poorly understood, but a spate of recent research has begun to unlock mechanisms that could one day adds years and extra pep to the human endgame.

In humans, the antidepressant mianserin prevents the neurotransmitter serotonin from being reabsorbed once it has been released by nerve cells in the brain, thus extending its impact.

Decreased levels of serotonin, a naturally occurring chemical that creates a feeling of well-being, have been linked in many studies to depression.

Linda Buck, a researcher at the Howard Hughes Institute in Seattle, Washington, and two colleagues screened 88,000 chemicals to see which might enhance the lifespan of Caenorhabiditis elegans, a short-lived worm commonly used in experiments on longevity.

In the experiments, a chemical virtually identical to the drug mianserin extended the lives of worms by 30 percent, according to the study.

Three other compounds that also act on serotonin also had a similar effect: mirtazapine, methiothepin and cyproheptadine.

The antidepressant notably blocked uptake of another neurotransmitter, octopamine, which has a role in releasing fat from fat cells.

This links to previous studies showing that lab animals which were kept on a low-calorie diet live longer, said Buck, who won the 2004 Nobel for medicine for research on the human olfactory system.

What determines lifespan remains poorly understood, but a spate of recent research has begun to unlock mechanisms that could one day adds years and extra pep to the human endgame.

In humans, the antidepressant mianserin prevents the neurotransmitter serotonin from being reabsorbed once it has been released by nerve cells in the brain, thus extending its impact.

Decreased levels of serotonin, a naturally occurring chemical that creates a feeling of well-being, have been linked in many studies to depression.

Linda Buck, a researcher at the Howard Hughes Institute in Seattle, Washington, and two colleagues screened 88,000 chemicals to see which might enhance the lifespan of Caenorhabiditis elegans, a short-lived worm commonly used in experiments on longevity.

In the experiments, a chemical virtually identical to the drug mianserin extended the lives of worms by 30 percent, according to the study.

Three other compounds that also act on serotonin also had a similar effect: mirtazapine, methiothepin and cyproheptadine.

The antidepressant notably blocked uptake of another neurotransmitter, octopamine, which has a role in releasing fat from fat cells.

This links to previous studies showing that lab animals which were kept on a low-calorie diet live longer, said Buck, who won the 2004 Nobel for medicine for research on the human olfactory system.