Effect of acute tryptophan depletion on the response to controllable and uncontrollable noise stress

Acute Tryptophan Depletion in Healthy Volunteers Enhances Punishment Prediction but Does not Affect Reward Prediction

“…In keeping with this hypothesis, recent neuroimaging observations suggest that the PFC controls amygdala activity when subjects are presented with negatively valenced stimuli (Ochsner et al, 2002;Phelps and LeDoux, 2005). Based on previous suggestions that 5-HT conveys resilience to adversity (Deakin and Graeff, 1991;Deakin, 1991;Richell et al, 2005), we hypothesize that ATD disrupts PFC-mediated control over subcortical brain regions, such as the amygdala and/or the dorsal raphe nucleus (Amat et al, 2005;Heinz et al, 2005;Pezawas et al, 2005). Such a top-down control failure may interact with reductions in 'background' levels of tonic 5-HT to bias the system toward anticipation of adversity (by increasing prediction errors for future punishment).…”

Impaired recognition of fear facial expressions in 5-HTTLPR S-polymorphism carriers following tryptophan depletion

“…The modulation of serotonin levels affects anxiety symptoms after anxiogenic challenges (Richell et al 2005;Schruers et al 2000) and sensitivity to fear-relevant social cues (Harmer et al 2003a(Harmer et al ,b, 2004Munafo et al 2006). Acute tryptophan depletion (ATD), a standard method of reducing brain synthesis of serotonin, is associated with decrements in the recognition of the fear facial expression (Harmer et al 2003b).…”

Neurobiological Background of Affective Disorders

“…The serotonin system originates from the dorsal and medial raphe nuclei in the brainstem infringing on limbic structures such as the hippocampus and amygdala [94]. Reducing serotonin synthesis induces depressive symptoms in healthy probands exposed to uncontrollable stress [96], and increased serotonin release in the hippocampus has been implicated in the mechanisms underlying coping with stress [97]. Serotonin (5-HT) receptors are represented by 5-HT1 class receptors, being situated pre-and postsynaptically and inhibitory by reduction of adenylate cyclase activity.…”