Stimulating effects of the antihistamine fexofenadine: testing the dopamine transporter hypothesis.

Rationale: First- and second-generation antihistamines are known to produce different degrees of sedation. However, a few studies have shown that the H1-antagonist fexofenadine produces mild stimulating effects. One hypothesis suggests that this is due to fexofenadine producing an increase in dopamine levels by blocking the dopamine transporter.

The effect of acute tryptophan depletion on the BOLD response during performance monitoring and response inhibition in healthy male volunteers.

Rationale: Serotonin (5-HT) was implicated in both clinical and experimental studies in flexible, goal-directed behavior. However, the way in which 5-HT manipulations affect brain activation patterns underlying different subprocesses of cognitive flexibility remains largely unknown.

Objectives: The aim of this study was to investigate the effect of a transient lowering of 5-HT on brain activation during performance monitoring and response inhibition.

Acute tryptophan depletion reduces activation in the right hippocampus during encoding in an episodic memory task.

Acute tryptophan depletion (ATD), a well-recognized method to lower central serotonin levels, was used to examine the effects of lower central serotonin levels on memory function in healthy males. Functional Magnetic Resonance Imaging (fMRI) was used to examine changes in brain activation during the encoding and the retrieval phase of a visual verbal episodic memory task. ATD led to more positively rated words in the encoding phase and to poorer recognition of these positively rated words in the retrieval phase.