Seasonal changes, like the isolation of winter can cause Seasonal Affective Disorder (SAD) in both humans and animals. SAD is characterized by depression, trouble sleeping, decreased libido, changes in appetite, withdrawing from social situations, and even suicidal feelings. A group of researchers from the Institute of Transformative Bio-Molecules (WPI-ITbM) at Nagoya University in Japan studied the underlying cause of winter depression and found a drug that helps alleviate this depression in medaka fish.
Medaka are a small fish and frequently used in research on complex brain disorders. Medaka are especially useful for studying pharmacology. They were also found to be a good model for winter depression-like SAD. When exposed to winter-like conditions, the medaka presented with increased anxiety and decreased sociability.
To study the underlying causes of SAD, the researchers used chemical genomics to identify that a traditional Chinese medicine called celastrol, was successful in alleviating winter sadness. NRF2, a celastrol target, is a basic leucine zipper (bZIP) protein that can protect against oxidative stress and is known to play a role in depression.
Depression can be the result of a harsh environment. Human patients with SAD had similar symptoms and behaviors to the medaka when exposed to winter conditions. This provides some insight into how winter depression works and the possible NRF2 therapies.