Orita K, Sasaki S, Maeda M, Hashimoto A, Nishikawa T, Yugami T, Umezu K. Synthesis and evaluation of 1-(1-[5-(2'-[18F]fluoroethyl)-2-thienyl]-cyclohexyl)piperidine as a potential in vivo radioligand for the NMDA receptor-channel complex.
Nucl Med Biol 1993;
20:865-73. [PMID:
8241999 DOI:
10.1016/0969-8051(93)90153-l]
[Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
1-(1-[5-(2'-[18F]Fluoroethyl)-2-thienyl]cyclohexyl)piperidine (18FE-TCP) was prepared as a fluorine-substituted analogue of the potent NMDA receptor channel blocker, 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP), by the mesylate displacement with [18F]fluoride ion with isolated radiochemical yields of 6-12%, and the synthesis time including a two step HPLC purification was 120 min. The regional distribution in rat brain after i.v. injection of 18FE-TCP was heterogeneous and similar to the known distribution of phencyclidine recognition sites, with hippocampus-cerebellum, striatum-cerebellum and cerebral cortex-cerebellum concentration ratios of 2.08, 1.7 and 1.54, respectively, 15 min post-injection. Furthermore, this localized regional cerebral distribution was blocked by co-injection with the unlabelled FE-TCP or pretreatment with cis-2-hydroxymethyl-r-1-(N-piperidyl)-1-(2-thienyl)cyclohexane, with the greatest reductions seen in the hippocampus followed by the striatum and cerebral cortex. However, relatively low receptor binding affinity and high non-specific binding due to its high lipophilicity suggest that 18FE-TCP may not be a suitable radioligand for in vivo PET investigations of the NMDA receptor-channel complex.
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