title: Progress in the characterization of the opioid receptor subtypes: peptides as probes. Future directions.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D007700:Kinetics; D010455:Peptides / Q000378:metabolism*; D011957:Receptors, Opioid / Q000378:metabolism*; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D017480:Receptors, sigma; D013379:Substrate Specificity
chemical_list: D010455:Peptides; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D017480:Receptors, sigma