Opioid peptides.
D000698:Analgesia; D006801:Humans; D009892:Opium / Q000031:analogs & derivatives* / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D011957:Receptors, Opioid / Q000187:drug effects; D013329:Structure-Activity Relationship; D019966:Substance-Related Disorders; D009435:Synaptic Transmission
D010455:Peptides; D011957:Receptors, Opioid; D009892:Opium