A team of French scientists, led by a McGill University psychiatrist, has produced a breed of perpetually happy mice.
The researchers hope the genetically engineered mice can be used in research to treatdepression.
The mice are bred so that they are missing a gene called TREK-1, which is linked to the transmission of serotonin in the brain.
Serotonin is a neurotransmitter that plays in important role in mood, sleep and sexual desire.
The mice without the TREK-1 gene, called "knockout" mice, were created and bred in France at the University of Nice. Theyappear to be resistant to depression.
The altered mice were given a series of separate behavioural and chemical tests used to measure mood in animals.
"The results really surprised us. Our 'knock-out' mice acted as if they had been treated with antidepressants for at least three weeks," said Guy Debonnel, a psychiatry professor at McGill University and lead author of the study.
The research appears this week in the journal Nature Neuroscience.
The researchers say this is the first time that depression has been eliminated in a lab animal through genetic manipulation.
Debonnel said the finding could lead to more effective antidepressants.
"Current medications for clinical depression are ineffective for a third of patients, which is why the development of alternate treatments is so important," said Debonnel.
About eight per cent of Canadians will suffer from depression at some point in their lives, according to data from Health Canada and Statistics Canada.