Figure 4.

Amygdala serotonin reuptake inhibition reduced physiological and behavioral expression of conditioned threat. A, During acquisition of threat conditioning, animals (n = 6) showed a robust elevation in cardiovascular response (MAP) to US⁺ presentation. Values are expressed as the increase in MAP relative to the average MAP of the 5 s before US⁺ onset. Data are shown from US⁺ onset (0–5 s), and 5 s after its termination (+1 to +5 s). Graphs show the change in CS-directed (B) MAP and (C) hypervigilant behavior of bilateral saline (blue) and citalopram (orange; 30 μg/site) blocks across trials for conditioning, extinction, and extinction recall sessions (shading indicates SEM). During conditioning, animals showed significant peak CS-directed MAP and hypervigilant behavior with no differences in conditioning between blocks (left graphs). During extinction, amygdala serotonin reuptake inhibition significantly reduced the expression of CS-directed MAP and CS-directed hypervigilant behavior across trial pairs (middle graphs; *significant effects of manipulation and trial, and significant interaction between the effects of both, p < .05). On extinction recall session, CS-directed MAP and hypervigilant behavior generally declined over trial pairs but there was no effect of manipulation or interaction(right graphs).