Scientists at Penn State University say they have developed a mouse that gets depressed in a similar fashion to humans, which could lead to better treatment for the condition among people.

Biology professor Bernhard Luscher, the project's leader, said that is because scientists will be able to test different drugs for various mental conditions and observe the mice to see the results.

"A mouse can't tell us if it is feeling depressed, so we used a number of different kinds of tests to gauge ... changes ... of a type of depression that, in humans, does not respond well to some antidepressant drugs," Luscher said.

Drug trials

Researchers essentially created a rodent with a genetic defect that interferes with the development of a protein in the brain, called the GABA-A receptor. The lack of that protein allows the mice to mimic brain disorders among humans but lets the researchers reach different conclusions, the scientists noted.

For example, a GABA-A deficiency had been linked to anxiety disorders but not directly to depression.

In a paper to be published in Biology Psychiatry, however, Luscher used the genetically modified mouse to show that the protein is in fact important to proper brain function and that whatever cerebral problems cause anxiety also have a hand in the appearance of depression.

Similar brains

As well, the brain physiology of the mice is similar to the 30 per cent of people with depression who do not improve by using known drugs, such fluoxetine, also known by the brand name Prozac.

Doctors, faced with treating mentally ill patients, often try one drug after another in an effort to find one that will be effective. That means scientists often do not have enough time to see whether one medication is working before another is introduced.

The laboratory mice should allow researchers sufficient time to ascertain whether a single drug is effective in treating a particular condition, scientists said.