A brain mechanism that may be responsible for postpartum depression in women has been uncovered by researchers from University of California at Los Angeles.

The team has identified a suspect protein in mice that may promote depression-like behaviours.

"For the first time, we may have a highly useful model of postpartum depression," said NIMH Director Dr Thomas R. Insel.

"The new research also points to a specific potential new target in the brain for medications to treat this disorder that affects 15 percent of women after they give birth," he added.

During the study the researchers used a genetically engineered mice lacking a protein critical for adapting to the sex hormone fluctuations of pregnancy and the postpartum period.

"After giving birth, female mice deficient in the suspect protein showed depression-like behaviors and neglected their newborn pups," said Istvan Mody, Ph.D., lead researcher, of the University of California at Los Angeles,

"Giving a drug that restored the protein's function improved maternal behavior and reduced pup mortality," Mody added.

Researchers Mody and Jamie Maguire assumed that postpartum depression was the result of marked fluctuations in estrogen and progesterone that accompany pregnancy and childbirth

Yet manipulating the hormones experimentally triggers depression only in women with a history of the disorder. The roots of their vulnerability remain a mystery.

Previous studies have made it evident that the hormones exert their effects on mood through the brain's major inhibitory chemical messenger system, called GABA, which dampens neural activity, helping to regulate when a neuron fires.