A non-peptide fluorescent probe, NTI4F, has been developed for the delta (δ) opioid receptor. The probe is a potent δ-antagonist in the mouse vas deferens (MVD) smooth muscle assay and it binds to the δ opioid receptor with high affinity (K(i) = 1 nM) and selectivity. Confocal microscopy indicates that the probe binds to Madin-Darby canine kidney (MDCK) cells transfected with the δ opioid receptor. This binding can be blocked by the δ opioid receptor antagonist, naltrindole (NTI), but not by morphine or ethylketazocine (EK) which are mu (μ)- and kappa (κ)-selective ligands. This fluorescent probe should prove useful in the study of the distribution of the δ opioid receptor.
- Delta opioid receptor
- Fluorescent probe