R Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, CH-8058 Zurich, Switzerland

R Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, CH-8058 Zurich, Switzerland Division of Psychology, University of Fribourg, CH-1700 Fribourg, Switzerland; [email protected] Correspondence: [email protected] or [email protected]: Cumming, P.; Scheidegger, M.; Dornbierer, D.; Palner, M.; Quednow, B.B.; Martin-Soelch, C. Molecular and Functional Imaging Studies of Psychedelic Drug Action in Animals and Humans. Molecules 2021, 26, 2451. https://doi.org/10.3390/ molecules26092451 Academic Editors: Mauricio Morais and P er Kele Received: 8 March 2021 Accepted: 19 April 2021 Published: 22 AprilPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Copyright: 2021 by the authors. Licensee MDPI, Basel, Switzerland. This short article is definitely an open access article distributed beneath the terms and situations of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ four.0/).Abstract: Hallucinogens are a loosely defined group of compounds like LSD, N,Ndimethyltryptamines, mescaline, psilocybin/psilocin, and two,5-dimethoxy-4-methamphetamine (DOM), which can evoke intense visual and emotional experiences. We are witnessing a renaissance of investigation interest in hallucinogens, driven by growing awareness of their psychotherapeutic possible. As such, we now present a narrative critique on the literature on Pyk2 Source hallucinogen binding in vitro and ex vivo, plus the a variety of molecular imaging research with positron emission tomography (PET) or single photon emission pc tomography (SPECT). Normally, molecular imaging can depict the uptake and binding distribution of labelled hallucinogenic compounds or their congeners Myosin Storage & Stability inside the brain, as was shown in an early PET study with N1 -([11 C]-methyl)-2-bromo-LSD ([11 C]-MBL); displacement together with the non-radioactive competitor ketanserin confirmed that the majority of [11 C]-MBL specific binding was to serotonin 5-HT2A receptors. However, interactions at serotonin 5HT1A along with other classes of receptors and pleotropic effects on second messenger pathways may perhaps contribute towards the specific experiential phenomenologies of LSD and other hallucinogenic compounds. Other salient aspects of hallucinogen action include things like permeability to the blood rain barrier, the rates of metabolism and elimination, and the formation of active metabolites. Regardless of the maturation of radiochemistry and molecular imaging in current years, there has been only a handful of PET or SPECT research of radiolabeled hallucinogens, most recently utilizing the 5-HT2A/2C agonist N-(2[11 CH3 O]methoxybenzyl)-2,5-dimethoxy- 4-bromophenethylamine ([11 C]Cimbi-36). As well as PET studies of target engagement at neuroreceptors and transporters, there is a modest quantity of studies on the effects of hallucinogenic compounds on cerebral perfusion ([15 O]-water) or metabolism ([18 F]fluorodeoxyglucose/FDG). There remains considerable scope for basic imaging research on the web-sites of interaction of hallucinogens and their cerebrometabolic effects; we count on that hybrid imaging with PET in conjunction with functional magnetic resonance imaging (fMRI) should really give specially valuable for the next phase of this research. Key phrases: hallucinogens; molecular imaging; PET; SPECT; serotonin receptorsMolecules 2021, 26, 2451. https://doi.org/10.3390/moleculeshttps://www.mdpi.com/journal/moleculesMolecules 2021, 26,2 ofContents: 1.