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.
Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building blocks of RNA (and its derivative deoxyadenosine is a building block of DNA), which are essential for all life on earth. Its derivatives include the energy carriers adenosine mono-, di-, and triphosphate, also known as AMP/ADP/ATP. Cyclic adenosine monophosphate (cAMP) is pervasive in signal transduction. Adenosine is used as an intravenous medication for some cardiac arrhythmias.
The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a different gene.
The adenosine A1 receptor (A1AR) is one member of the adenosine receptor group of G protein-coupled receptors with adenosine as endogenous ligand.
A heteromer is something that consists of different parts; the antonym of homomeric. Examples are:
The adenosine A2A receptor, also known as ADORA2A, is an adenosine receptor, and also denotes the human gene encoding it.
The adenosine A2B receptor, also known as ADORA2B, is a G-protein coupled adenosine receptor, and also denotes the human adenosine A2b receptor gene which encodes it.
SCH-58261 is a drug which acts as a potent and selective antagonist for the adenosine receptor A2A, with more than 50x selectivity for A2A over other adenosine receptors. It has been used to investigate the mechanism of action of caffeine, which is a mixed A1 / A2A antagonist, and has shown that the A2A receptor is primarily responsible for the stimulant and ergogenic effects of caffeine, but blockade of both A1 and A2A receptors is required to accurately replicate caffeine's effects in animals. SCH-58261 has also shown antidepressant, nootropic and neuroprotective effects in a variety of animal models, and has been investigated as a possible treatment for Parkinson's disease.
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.
Augmentation, in the context of the pharmacological management of psychiatry, refers to the combination of two or more drugs to achieve better treatment results. Examples include:
5-I-R91150 is a compound that acts as a potent and selective antagonist of 5-HT2A receptors. Its main application is as its iodine-123 radiolabeled form, in which it can be used in SPECT scanning in human neuroimaging studies, to examine the distribution of the 5-HT2A receptor subtype in the brain, e.g. with respect to sex and age and in adults with Asperger syndrome or Alzheimer's disease.
ZM-241,385 is a high affinity antagonist ligand selective for the adenosine A2A receptor.
Preladenant was a drug that was developed by Schering-Plough which acted as a potent and selective antagonist at the adenosine A2A receptor. It was being researched as a potential treatment for Parkinson's disease. Positive results were reported in Phase II clinical trials in humans, but it did not prove itself to be more effective than a placebo during Phase III trials, and so was discontinued in May 2013.
CGS-15943 is a drug which acts as a potent and reasonably selective antagonist for the adenosine receptors A1 and A2A, having a Ki of 3.3nM at A2A and 21nM at A1. It was one of the first adenosine receptor antagonists discovered that is not a xanthine derivative, instead being a triazoloquinazoline. Consequently, CGS-15943 has the advantage over most xanthine derivatives that it is not a phosphodiesterase inhibitor, and so has more a specific pharmacological effects profile. It produces similar effects to caffeine in animal studies, though with higher potency.
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.
Purinergic signalling is a form of extracellular signalling mediated by purine nucleotides and nucleosides such as adenosine and ATP. It involves the activation of purinergic receptors in the cell and/or in nearby cells, thereby regulating cellular functions.
Aticaprant, also known by its developmental codes JNJ-67953964, CERC-501, and LY-2456302, is a κ-opioid receptor (KOR) antagonist which is under development for the treatment of major depressive disorder. A regulatory application for approval of the medication is expected to be submitted by 2025. Aticaprant is taken by mouth.
