Love hormone has a dark side! The fuzzy, warm hormone oxytocin, long known to promote feelings of love, social bonding and well-being, can also cause emotional pain, by strengthening bad memories and increasing fear and anxiety, a new study has claimed. Oxytocin appears to be the reason stressful social situations, perhaps being bullied at school or tormented by a boss, reverberate long past the event and can trigger fear and anxiety in the future.
That's because the hormone actually strengthens social memory in one specific region of the brain, researchers from Northwestern University in the US have found. If a social experience is negative or stressful, the hormone activates a part of the brain that intensifies the memory. Oxytocin also increases the susceptibility to feeling fearful and anxious during stressful events going forward. The research, which was done in mice, is particularly relevant because oxytocin currently is being tested as an anti-anxiety drug in several clinical trials.
"By understanding the oxytocin system's dual role in triggering or reducing anxiety, depending on the social context, we can optimise oxytocin treatments that improve well-being instead of triggering negative reactions," said Jelena Radulovic, the senior author of the study. This is the first study to link oxytocin to social stress and its ability to increase anxiety and fear in response to future stress.
Scientists also discovered the brain region responsible for these effects - the lateral septum - and the pathway or route oxytocin uses in this area to amplify fear and anxiety. The scientists discovered that oxytocin strengthens negative social memory and future anxiety by triggering an important signalling molecule - ERK (extracellular signal regulated kinases) - that becomes activated for six hours after a negative social experience.ERK causes enhanced fear, Radulovic believes, by stimulating the brain's fear pathways, many of which pass through the lateral septum. The region is involved in emotional and stress responses.
The findings surprised the researchers, who were expecting oxytocin to modulate positive emotions in memory, based on its long association with love and social bonding. "Oxytocin is usually considered a stress-reducing agent based on decades of research," said Yomayra Guzman, a doctoral student in Radulovic's lab and the study's lead author. "With this novel animal model, we showed how it enhances fear rather than reducing it and where the molecular changes are occurring in our central nervous system," Guzman said. The study was published in the journal Nature Neuroscience.
