| opioid peptides | The endogenous peptides with opiate-like activity. The three major classes currently recognised are the enkephalins, the dynorphins, and the endorphins. Each of these families derives from different precursors, proenkephalin, prodynorphin, and pro-opiomelanocortin, respectively. There are also at least three classes of opioid receptors, but the peptide families do not map to the receptors in a simple way. (12 Dec 1998) |
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| opioid receptor | <pharmacology> A membrane protein, widely distributed in animal cells, but especially in the brain (enkephalin receptors) and gut. The natural ligands are the opiate peptide neurotransmitters, but the name is given because opiates are potent agonists that occupy the receptors and mimic the action of the natural transmitters. (18 Nov 1997) |
| opioid-related disorders | Disorders related or resulting from abuse or mis-use of opioids. (12 Dec 1998) |