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 Department 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 Research 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: eight March 2021 Accepted: 19 April 2021 Published: 22 AprilPublisher’s Note: MDPI stays neutral with regard to Bradykinin B2 Receptor (B2R) Formulation jurisdictional claims in published maps and institutional affiliations.Copyright: 2021 by the authors. Licensee MDPI, Basel, Switzerland. This short article is an open access article distributed below the terms and situations from the Inventive Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ four.0/).Abstract: Hallucinogens are a IL-17 drug 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 analysis interest in hallucinogens, driven by escalating awareness of their psychotherapeutic possible. As such, we now present a narrative overview of the literature on hallucinogen binding in vitro and ex vivo, and the numerous molecular imaging research with positron emission tomography (PET) or single photon emission computer tomography (SPECT). In general, molecular imaging can depict the uptake and binding distribution of labelled hallucinogenic compounds or their congeners within the brain, as was shown in an early PET study with N1 -([11 C]-methyl)-2-bromo-LSD ([11 C]-MBL); displacement with all the non-radioactive competitor ketanserin confirmed that the majority of [11 C]-MBL certain binding was to serotonin 5-HT2A receptors. Nonetheless, interactions at serotonin 5HT1A and also other classes of receptors and pleotropic effects on second messenger pathways might contribute to the distinct experiential phenomenologies of LSD as well as other hallucinogenic compounds. Other salient aspects of hallucinogen action include things like permeability towards the blood rain barrier, the rates of metabolism and elimination, along with the formation of active metabolites. Regardless of the maturation of radiochemistry and molecular imaging in recent years, there has been only a handful of PET or SPECT research of radiolabeled hallucinogens, most recently using the 5-HT2A/2C agonist N-(2[11 CH3 O]methoxybenzyl)-2,5-dimethoxy- 4-bromophenethylamine ([11 C]Cimbi-36). Along with PET research of target engagement at neuroreceptors and transporters, there is a modest variety of research around the effects of hallucinogenic compounds on cerebral perfusion ([15 O]-water) or metabolism ([18 F]fluorodeoxyglucose/FDG). There remains considerable scope for fundamental imaging investigation on the internet sites of interaction of hallucinogens and their cerebrometabolic effects; we anticipate that hybrid imaging with PET in conjunction with functional magnetic resonance imaging (fMRI) really should supply in particular beneficial for the subsequent phase of this investigation. Keyword 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.