Synthesis and Evaluation of a 64Cu-Conjugate, a Selective δ-Opioid Receptor Positron Emission Tomography Imaging Agent

Given the putative selectivity of the antagonist TIPP (Tyr-Tic-Phe-Phe) for δ-opioid receptors (DOP), this compound was selected for the design of a novel 64Cu-radiolabeled potent and selective DOP positron emission tomography (PET) imaging agent. Ex vivo autoradiography of TIPPD-PEG-K(NOTA/64Cu)-NH2 on rat brain sections produced a distribution pattern consistent with the known expression of DOP. Taken together, the in vitro and ex vivo data indicate that this 64Cu-tracer holds promise for studying the DOP by means of PET.