A new breed of permanently ‘cheerful’ mouse is providing hope of a new treatment for clinical depression. TREK-1 is a gene that can affect transmission of serotonin in the brain. Serotonin is known to play an important role in mood, sleep and sexuality. By breeding mice with an absence of TREK-1, researchers were able create a depression-resistant strain. The details of this research, which involved an international collaboration with scientists from the University of Nice, France, are published in Nature Neuroscience this week.