Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption. Different tracers are used for various imaging purposes, depending on the target process within the body.
The serotonin transporter also known as the sodium-dependent serotonin transporter and solute carrier family 6 member 4 is a protein that in humans is encoded by the SLC6A4 gene. SERT is a type of monoamine transporter protein that transports the neurotransmitter serotonin from the synaptic cleft back to the presynaptic neuron, in a process known as serotonin reuptake.
A radioligand is a radioactive biochemical substance, in particular, a ligand that is radiolabeled. Radioligands are used for diagnosis or for research-oriented study of the receptor systems of the body, and for anti-cancer radioligand therapy.
Ketanserin (INN, USAN, BAN) (brand name Sufrexal; former developmental code name R41468) is a drug used clinically as an antihypertensive agent and in scientific research to study the serotonergic system; specifically, the 5-HT2 receptor family. It was discovered at Janssen Pharmaceutica in 1980. It is not available in the United States.
The 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor (GPCR). The 5-HT2A receptor is a cell surface receptor, but has several intracellular locations.
5-Hydroxytryptamine receptor 4 is a protein that in humans is encoded by the HTR4 gene.
The serotonin 1A receptor is a subtype of serotonin receptors, or 5-HT receptors, that binds serotonin, also known as 5-HT, a neurotransmitter. 5-HT1A is expressed in the brain, spleen, and neonatal kidney. It is a G protein-coupled receptor (GPCR), coupled to the Gi protein, and its activation in the brain mediates hyperpolarization and reduction of firing rate of the postsynaptic neuron. In humans, the serotonin 1A receptor is encoded by the HTR1A gene.
Altanserin is a compound that binds to the 5-HT2A receptor. Labeled with the isotope fluorine-18 it is used as a radioligand in positron emission tomography (PET) studies of the brain, i.e., studies of the 5-HT2A neuroreceptors. Besides human neuroimaging studies altanserin has also been used in the study of rats.
DASB, also known as 3-amino-4-(2-dimethylaminomethylphenylsulfanyl)-benzonitrile, is a compound that binds to the serotonin transporter. Labeled with carbon-11 — a radioactive isotope — it has been used as a radioligand in neuroimaging with positron emission tomography (PET) since around year 2000. In this context it is regarded as one of the superior radioligands for PET study of the serotonin transporter in the brain, since it has high selectivity for the serotonin transporter.
WAY-100635 is a piperazine drug and research chemical widely used in scientific studies. It was originally believed to act as a selective 5-HT1A receptor antagonist, but subsequent research showed that it also acts as potent full agonist at the D4 receptor. It is sometimes referred to as a silent antagonist at the former receptor. It is closely related to WAY-100135.
Nisoxetine, originally synthesized in the Lilly research laboratories during the early 1970s, is a potent and selective inhibitor for the reuptake of norepinephrine (noradrenaline) into synapses. It currently has no clinical applications in humans, although it was originally researched as an antidepressant. Nisoxetine is now widely used in scientific research as a standard selective norepinephrine reuptake inhibitor. It has been used to research obesity and energy balance, and exerts some local analgesia effects.
The free fraction is a parameter in pharmacokinetics and receptor-ligand kinetics. One speaks of two different free fractions:
Jeffrey H. Meyer is a scientist and professor working with mood and anxiety disorders using neuroimaging at the Department of Psychiatry, University of Toronto. He is currently the head of the Neurochemical Imaging Program in Mood and Anxiety Disorders in the Brain Health Imaging Centre at the Campbell Family Mental Health Research Institute and is working as a Senior Scientist in the General and Health Systems Psychiatry Division at the Centre for Addiction and Mental Health. He has also been awarded with the Tier 1 Canada Research Chair in the Neurochemistry of Major Depression.
5-HTTLPR is a degenerate repeat polymorphic region in SLC6A4, the gene that codes for the serotonin transporter. Since the polymorphism was identified in the middle of the 1990s, it has been extensively investigated, e.g., in connection with neuropsychiatric disorders. A 2006 scientific article stated that "over 300 behavioral, psychiatric, pharmacogenetic and other medical genetics papers" had analyzed the polymorphism. While often discussed as an example of gene-environment interaction, this contention is contested.
25B-NBOMe is a derivative of the phenethylamine psychedelic 2C-B, discovered in 2004 by Ralf Heim at the Free University of Berlin. It acts as a potent full agonist for the 5HT2A receptor. Anecdotal reports from users suggest 25B-NBOMe to be an active hallucinogen at a dose of as little as 250–500 µg, making it a similar potency to other phenethylamine derived hallucinogens such as Bromo-DragonFLY. Duration of effects lasts about 12–16 hours, although the parent compound is rapidly cleared from the blood when used in the radiolabeled form in tracer doses. Recently, Custodio et al (2019) evaluated the potential involvement of dysregulated dopaminergic system, neuroadaptation, and brain wave changes which may contribute to the rewarding and reinforcing properties of 25B-NBOMe in rodents.
5-OH-DPAT is a synthetic compound that acts as a dopamine receptor agonist with selectivity for the D2 receptor and D3 receptor subtypes. Only the (S)-enantiomer is active as an agonist, with the (R)-enantiomer being a weak antagonist at D2 receptors. Radiolabelled 11C-5-OH-DPAT is used as an agonist radioligand for mapping the distribution and function of D2 and D3 receptors in the brain, and the drug is also being studied in the treatment of Parkinson's disease.
Brain positron emission tomography is a form of positron emission tomography (PET) that is used to measure brain metabolism and the distribution of exogenous radiolabeled chemical agents throughout the brain. PET measures emissions from radioactively labeled metabolically active chemicals that have been injected into the bloodstream. The emission data from brain PET are computer-processed to produce multi-dimensional images of the distribution of the chemicals throughout the brain.
Mefway is a serotonin 5-HT1A receptor antagonist used in medical research, usually in the form of mefway (18F) as a positron emission tomography (PET) radiotracer.
DPA-713 or N,N-diethyl-2-(4-methoxyphenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidine-3-acetamide is a selective ligand for the translocator protein (TSPO).
Dihydrotetrabenazine or DTBZ is an organic compound with the chemical formula C19H29NO3. It is a close analog of tetrabenazine. DTBZ and its derivatives, when labeled with positron emitting isotopes such as carbon-11 and fluorine-18, are used as PET radioligands for examining VMAT2.
