Food-derived serotonergic modulators: effects on mood and cognition.

The most frequently described drugs in the treatment of mood disorders are selective serotonin reuptake and monoamine oxidase (MAO) inhibitors, enhancing serotonin levels in the brain. However, side-effects have been reported for these drugs. Because serotonin levels in the brain are dependent on the availability of the food-derived precursor tryptophan, foods such as chicken, soyabeans, cereals, tuna, nuts and bananas may serve as an alternative to improve mood and cognition. Here we discuss the effects of high- or low-tryptophan-containing food, as well as plant extracts with a modest monoamine reuptake and MAO-A inhibition functional profile, on mood and cognition in healthy and vulnerable human subjects and rodents. Together the studies suggest that there is an inverted U-shaped curve for plasma tryptophan levels, with low and too high tryptophan levels impairing cognition, and moderate to high tryptophan levels improving cognition. This relationship is found for both healthy and vulnerable subjects. Whereas this relationship may also exist for mood, the inverted U-shaped curve for plasma tryptophan levels and mood may be based on different tryptophan concentrations in healthy v. vulnerable individuals. Animal studies are emerging and allow further understanding of effects and the mode of action of food-derived serotonergic components on mood, cognition and mechanisms. Ultimately, insight into the concentrations of tryptophan and other serotonergic components in food having beneficial effects on mood and cognition in healthy, but particularly vulnerable, subjects may support well-being in our highly demanding society.

Behavioural and neuroplastic properties of chronic lurasidone treatment in serotonin transporter knockout rats.

Second-generation antipsychotics (SGA) are multi-target agents widely used for the treatment of schizophrenia and bipolar disorder that also hold potential for the treatment of impaired emotional control, thanks to their diverse receptor profiles as well as their potential in modulating neuroadaptive changes in key brain regions. The aim of this study was thus to establish the ability of lurasidone, a novel SGA characterized by a multi-receptor signature, to modulate behavioural and molecular defects associated with a genetic model of impaired emotional control, namely serotonin transporter knockout (SERT KO) rats. At behavioural level, we found that chronic lurasidone treatment significantly increased fear extinction in SERT KO rats, but not in wild-type control animals. Moreover, at molecular level, lurasidone was able to normalize the reduced expression of the neurotrophin brain-derived neurotrophic factor in the prefrontal cortex of SERT KO rats, an effect that occurred through the regulation of specific neurotrophin transcripts (primarily exon VI). Furthermore, chronic lurasidone treatment was also able to restore the reduced expression of different GABAergic markers that is present in these animals. Our results show that lurasidone can improve emotional control in SERT KO rats, with a primary impact on the prefrontal cortex. The adaptive changes set in motion by repeated treatment with lurasidone may in fact contribute to the amelioration of functional capacities, closely associated with neuronal plasticity, which are deteriorated in patients with schizophrenia, bipolar disease and major depression.