Local infusion of citalopram into the basolateral amygdala decreased conditioned fear of rats through increasing extracellular serotonin levels.

Selective serotonin reuptake inhibitors (SSRIs) are widely used for the treatment of depressive disorders and anxiety disorders. The anxiolytic mechanism of SSRIs is currently unclear. To investigate the anxiolytic effects of SSRIs, we measured both freezing behavior and extracellular serotonin and dopamine levels in the basolateral amygdala when rats were given conditioned fear stress under local reverse-dialysis of citalopram, an SSRI, into the basolateral amygdala. Local administration of citalopram into the basolateral amygdala significantly decreased freezing behavior induced by conditioned fear stress, and serotonin levels were simultaneously found to be significantly higher. Furthermore, repeated conditioned fear stress under local infusion of citalopram into the basolateral amygdala induced further increases in extracellular dopamine levels. Further studies investigating the role of dopamine in the amygdala for conditioned fear stress will be necessary. These results suggest that the basolateral amygdala is one of the target areas of the anxiolytic effects of citalopram and the increases of extracellular serotonin levels in the basolateral amygdala may be related to the anxiolytic effects.