Fluorescent neuroactive probes based on stilbazolium dyes

A set of spectrally diverse stilbazolium dyes was identified in an uptake assay using cultured brainstem and cerebellum cells isolated from e19 chicks. Pretreatment of cells with indatraline, a monoamine reuptake inhibitor, allowed identification of dyes that may interact with monoamine transporters. Two structurally related, yet spectrally segregated, probes, (E)-1-methyl-4-[2-(2-naphthalenyl)ethenyl]-pyridinium iodide (NEP+, 3A) and (E)-4-[2-(6-hydroxy-2-naphthalenyl)ethenyl]-1-methyl-pyridinium iodide (HNEP+, 4A), were selected and further investigated using HEK-293 cells selectively expressing dopamine, norepinephrine or serotonin transporters. HNEP+ was selectively accumulated via catecholamine transporters, with the norepinephrine transporter (NET) giving the highest response; NEP+ was not transported, though possible binding was observed. The alternate modes of interaction enable the use of NEP+ and HNEP+ to image distinct cell populations in live brain tissue explants. The preference for HNEP+ accumulation via NET was confirmed by imaging uptake in the absence and presence of desipramine, a norepinephrine reuptake inhibitor.