Fluorescent probes for adenosine receptors: Synthesis and biology of N6-dansylaminoalkyl-substituted neca derivatives

New fluorescent ligands for adenosine receptors are described; these compounds were obtained by the insertion, in the N6 position of NECA (a potent adenosine agonist), of dansylaminoalkyl moieties with alkyl spacers of increasing carbon chain length (from 3 to 12). Among them, the compound with a C6 alkyl spacer proved to be the most interesting one, showing a marked selectivity for the A1 receptor subtype; furthermore, in fluorescence microscopy assays it proved to be able to visualize and localize this receptor subtype at the level of the molecular layer of the rat cerebellar cortex.