Toronto, Feb 16 (IANS): Paving the way for new depression treatments, researchers have discovered the first-ever connection between vulnerability to depression and a type of brain cells called noradrenergic neurons.

Noradrenergic neurons are located in a cerebral structure named Locus coeruleus. These neurons communicate with each other using noradrenaline, a neurotransmitter molecule involved in emotional regulation, sleep and mood disorders - and, the researchers now believe, resilience and depression.

By combining pharmacological, genetic and optogenetic (activation of the neurons activity by a light beam) approaches, the research team showed that animals that cannot release noradrenaline are systematically vulnerable to depression following chronic stress.

"It is this control that steers the body's response toward resilience or toward vulnerability to depression," said one of the researchers Bruno Giros, professor of psychiatry at McGill University in Montreal, Canada.

This is not, however, an irreversible condition: increasing noradrenaline production results in higher resilience - and less depression, the study said.

Stressful life events--job loss, accident, death of a loved one--can trigger major depression in one person, but not in another.

A deciding factor is resilience, a biological mechanism that determines an individual's capacity to rebound from stressful or traumatic events.

The new findings shed light on how resilience works.

"Beyond this discovery about the brain mechanisms involved in depression, our results help explain how adrenergic drugs may work and could be used to treat major depression," Giros said.