Serotonin and molecular neuroimaging in humans using PET

Abstract

The serotonergic system is one of the most important modulatory neurotransmitter systems in the human brain. It plays a central role in major physiological processes and is implicated in a number of psychiatric disorders. Along with the dopaminergic system, it is also one of the phylogenetically oldest human neurotransmitter systems and one of the most diverse, with 14 different receptors identified up to this day, many of whose function remains to be understood. The system's functioning is even more diverse than the number of its receptors, since each is implicated in a number of different processes. This review aims at illustrating the distribution and summarizing the main functions of the serotonin (5-hydroxytryptamin, 5-HT) receptors as well as the serotonin transporter (SERT, 5-HTT), the vesicular monoamine transporter 2, monoamine oxidase type A and 5-HT synthesis in the human brain. Recent advances in in vivo quantification of these different receptors and enzymes that are part of the serotonergic system using positron emission tomography are described.

The Fabric of Meaning and Subjective Effects in LSD-Induced States Depend on Serotonin 2A Receptor Activation

“…Importantly, these regions also have a high 5-HT2AR density [38]. Furthermore, there were no significant differences in BOLD signal between drug treatment conditions when taking into account the meaningfulness rating provided by the participants after each trial, indicating that brain activity reflected differences in meaning processing as behaviorally reported by the participants.…”

Serotonin and Aversive Pavlovian Control of Instrumental Behavior in Humans

“…Thus, the serotonergic identity of these neurons is not known. In addition, there are also serotonin depletion studies in marmosets and humans emphasizing effects in the reward domain (Rogers et al, 2003;Cools et al, 2005;Man et al, 2011; may be reflecting interactions with dopamine). For example, we have shown that ATD abolished speeding of responding with increasing feedback likelihood in a monetary incentive delay like task (Cools et al, 2005).…”

“…Central TRP was depleted by ingesting an amino-acid load that did not contain TRP but did include other large neutral amino acids (LNAAs; Reilly et al, 1997). The quantities of amino acids in each drink were based on those used by Young et al (1985), although a 78.2 g mixture was used to minimize nausea.…”

Feasibility of ASL-based phMRI with a single dose of oral citalopram for repeated assessment of serotonin function

“…Second, PET and SPECT suffer from relatively low spatial resolution. Besides these practical limitations, until now studies using 5-HT radioligands have been less successful and are (consequently) less abundant than studies with for example dopaminergic radioligands (Paterson et al, 2011;Saulin et al, 2012;Smith et al, 2002). Thus, there is a clear need for novel, non-invasive methods to assess 5-HT function in humans and especially in psychiatric patients.…”