Worried mice provide insight into anxiety disorders
A circuit in the brain that makes mice prone to anxiety has been identified by an international team of researchers. The findings offer the hope of new therapies for people suffering from anxiety disorders. People with anxiety disorders are often prone to interpreting ambiguous situations as threatening. In this study, the scientists looked at mice lacking the serotonin receptor 1A. Brain cells use serotonin to communicate, and it plays an important role in brain development. The mice were found to have difficulties processing ambiguous stimuli and reacted to them with a full fear response. 'In humans serotonin signalling has been implicated in disorders including depression and anxiety and like our mice, patients suffering from these conditions also overreact to ambiguous situations,' commented lead researcher Cornelius Gross of the European Molecular Biology Laboratory (EMBL). Further work revealed that the absence of the 1A receptor had caused defects in the wiring in a region of the hippocampus, a part of the brain which is known to be involved in learning and memory. 'Shutting down a specific circuit in the hippocampus abolished fear reactions only to ambiguous cues,' explained Theodoros Tsetsenis of the EMBL, one of the authors of the study. 'The pathway must be involved in processing and assessing the value of stimuli. It seems to bias mice to interpret situations as threatening.' The work, which was led by the EMBL's Mouse Biology Unit in Italy, is published online by the journal nature Neuroscience.