Traceable Peptidic Ligands that Target Ghrelin Receptors.

Ghrelin is a 28-amino acid octanoylated peptide hormone that is implicated in many physiological and pathophysiological processes. Specific visualization of ghrelin and its cognate receptor using traceable ligands is crucial in elucidating the localization, functions and expression pattern of the peptide's signaling pathway. Here we review 12 representative radio- and fluorescently-labeled peptide-based ligands for in vitro and in vivo imaging studies. In particular, we focus on their structural features, pharmacological properties and applications in further biochemical research.