About 20 years ago. Deakin and Graeff proposed that whereas generalized anxiety disorder is produced by the overactivity of 5-HT excitatory projections from dorsal raphe nucleus to the areas of prefrontal cortex and amygdala which process distal threat, panic attacks are dyfunction of 5-HT inhibitory projections from dorsal raphe nucleus to the dorsal periqueductual gray matter, thereby releasing the responses to proximal threat, innate fear or anorexia. Besides, they suggested that the decrease in 5-HT1A neurotransmission in the hippocampus results in learned helpssness and depression.
