Los Angeles A protein has been identified that may determine why some women suffer acute depression after giving birth.

Experiments on mice reported in the journal Neuron suggest that the protein may be the key to surviving the changes in hormones during pregnancy and after giving birth.

Mice lacking this protein were more lethargic and less pleasure-seeking than ordinary mice. They also tended to ignore their pups and failed to make nests for them. When given a drug that made up for the lack of the protein, the mice behaved normally, and the survival of their pups improved.

The protein forms part of the system by which hormones affect mood. Receptors in the brain respond to a messenger chemical, gamma aminobutyric acid (GABA), which dampens the activity of brain cells. Levels of a particular GABA receptor fluctuate considerably during pregnancy. Scientists from the University of California, Los Angeles, reasoned that this might be the key to controlling mood during rapid changes in hormone levels.

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