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Radiolabeled Adrenergic and Muscarinic Blockers for in Vivo Studies
Published in William C. Eckelman, Lelio G. Colombetti, Receptor-Binding Radiotracers, 2019
The concentration of radioligand can be estimated from the specific activity. Although nuclear transformations are thought to produce carrier free radionuclides, in essence the term no-carrier-added is more appropriate.29 The methodology involved in in vitro assays has been described in another chapter.30
Review of brain imaging in anorexia and bulimia nervosa
Published in Stephen Wonderlich, James E Mitchell, Martina de Zwaan, Howard Steiger, Annual Review of Eating Disorders Part 2 – 2006, 2018
Walter H Kaye, Angela Wagner, Guido Frank, Ursula F Bailer
Brain-imaging studies in AN and BN can be divided into several categories. First, there has been substantial literature, using CT and more recently MRI, which seeks to determine whether there are brain structural alterations in individuals with EDs. Second, more recent studies have used functional magnetic resonance imaging (flvlRI) or other technologies to assess blood flow responses to some stimuli, such as pictures of food. Third are imaging studies, such as PET and SPECT, which employ a radioligand. These studies, which may use fluro-deoxyglucose (FDG) to study glucose metabolism or a ligand that is specific for a serotonin receptor, provide information that is specific for the system being studied, such as the 5-HT2A receptor.
Adrenoceptors: Classification and Distribution
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
Radioligand binding techniques are also useful for determining changes in receptor characteristics in clinical disorders or after drug treatments. Changes in adrenoceptor numbers have been observed in a wide range of diseased states. Scatchard analysis of the radioligand binding to tissue homogenates from patients has revealed reductions in cardiac β-adrenoceptor numbers in the ischaemic heart of cardiac failure patients as a fall in Bmax (Brodde 1991). Also, in asthmatic and cystic fibrosis patients there is a reported lowering of pulmonary β-adrenoceptors (Figure 3.3) (Sharma & Jeffery 1990). Chronic treatment with β-adrenoceptor agonists has also been shown to induce a fall in β-adrenoceptor number in the airways and lymphocytes, which may explain a possible tolerance to the bronchodilator effect of β-agonists (Conolly et al. 1982).
Design, synthesis, and evaluation of novel O-alkyl ferulamide derivatives as multifunctional ligands for treating Alzheimer’s disease
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Gaofeng Zhu, Ping Bai, Keren Wang, Jing Mi, Jing Yang, Jiaqi Hu, Yujuan Ban, Ran Xu, Rui Chen, Changning Wang, Lei Tang, Zhipei Sang
The in vivo whole-body distribution of [11C]5f was analysed at several scan time points (5, 15, 30, and 60 min). The mean radioactivity uptake in the organs of interest at each time point is presented in the histogram (Figure 12). The uptake of [11C]5f reached the highest concentration after injection at 5 min in the heart (14.20 ± 0.18%ID/cc), lung (9.5 ± 0.15%ID/cc), and spleen (11.4 ± 0.11%ID/cc) and gradually washed out from these organs. A high accumulation of radioligand was found in the liver and kidney, where the radioactivity steadily increased over time and achieved a maximum of 24.3 ± 0.16%ID/cc and 18.7 ± 0.13%ID/cc, respectively. The relatively high uptake in the liver and kidney indicated that [11C]5f is primarily excreted through the hepatobiliary and urinary pathways.
Distinct binding and signaling activity of Acthar Gel compared to other melanocortin receptor agonists
Published in Journal of Receptors and Signal Transduction, 2021
Y. Joyce Huang, Karen Galen, Ben Zweifel, Leah R. Brooks, A. Dale Wright
Following incubation, the samples were rapidly filtered under vacuum through glass fiber filters (GF/B, Packard) presoaked with 0.3% poly(ethyleneimine) and rinsed several times with ice-cold 50 mM Tris-HCl using a 96-sample cell harvester (UniFilter, Packard). The filters were dried and counted for radioactivity in a scintillation counter (TopCount, Packard) using a scintillation cocktail (MicroScintTM 0, Packard). Specific radioligand binding was calculated as the difference between total and nonspecific [125I]NDP-α-MSH binding in the absence and presence of NDP-α-MSH (1 μM), respectively. The results were expressed as percentage inhibition of the control radioligand-specific binding. All estimates of half maximal inhibitory concentration (IC50) were determined with a minimum of 2 replicates using nonlinear regression analysis and a 3-parameter dose-response curve with GraphPad Prism v. 7.03 for Windows (GraphPad Software, San Diego, CA).
A case study of foliglurax, the first clinical mGluR4 PAM for symptomatic treatment of Parkinson’s disease: translational gaps or a failing industry innovation model?
Published in Expert Opinion on Investigational Drugs, 2020
Dario Doller, Anton Bespalov, Rob Miller, Malgorzata Pietraszek, Mikhail Kalinichev
Throughout this work, the assumption is made that this radioligand will displace foliglurax, and these two compounds bind ‘to the same allosteric site of mGluR4’[62]. Of note, there is no in vitro data in any species confirming the displacement of compound 12b by foliglurax. Assuming that distinct chemotypes interacting allosterically with the mGluRs bind to the same binding site and displace each other is not warranted. Studies have shown that very minor differences in the structure of a drug and a radioligand can lead to unexpected results [74,75]. It has been recommended to de-risk such assumption by conducting the appropriate in vitro tests and confirm competitive behaviors for the pair drug-radioligand to be used in vivo in subsequent studies [74,75].