Arylacetamide-derived fluorescent probes: Synthesis, biological evaluation, and direct fluorescent labeling of k opioid receptors in mouse microglial cells

An Chih Chang, Chun C. Chao, Akira E. Takemori, Genya Gekker, Shuxian Hu, Phillip K. Peterson, Philip S. Portoghese

Research output: Contribution to journalReview articlepeer-review

22 Scopus citations

Abstract

Fluorescein isothiocyanate isomer I (FITC-I) conjugates of 2-(3,4-dichlorophenyl)-N-methyl-N-[1-(3- or 4-aminophenyl)-2-(1-pyrrolidinyl)ethyl]acetamide (10 and 14) were prepared either without or with an intervening mono-, di-, or tetraglycyl linker. The 3-substituted fluorescent probes (2-5) were found to retain potent agonist activity in smooth muscle preparations as well as high κ receptor affinity and selectivity in receptor binding assays. The 4-substituted series (6-9) were substantially less potent than the corresponding 3-substituted compounds. Flow cytometric analysis demonstrated high levels of direct κ-specific staining of mouse microglial cells by the fluorescent probe 5 containing a tetraglycyl linker, as indicated by a 41% decrease in percent cells positively labeled and a 61% decrease in mean fluorescence intensity in the presence of the κ-selective antagonist, norbinaltorphimine (norBNI). In similar studies, the probe 2 without a linker exhibited only nonspecific binding. This is the first report of direct, selective staining of κ opioid receptors by a fluorescent nonpeptide opioid ligand. The results of the present study illustrate the importance of introducing hydrophilic linkers to reduce nonspecific binding of fluorescent probes for opioid receptors.

Original languageEnglish (US)
Pages (from-to)1729-1735
Number of pages7
JournalJournal of medicinal chemistry
Volume39
Issue number8
DOIs
StatePublished - Apr 12 1996

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