| receptors, n-methyl-d-aspartate | A class of ionotropic glutamate receptors characterised by affinity for n-methyl-d-aspartate. Nmda receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity. (12 Dec 1998) |
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| receptors, odourant | Proteins, usually projecting from the cilia of olfactory receptor neurons, that specifically bind odourant molecules and trigger responses in the neurons. The large number of different odourant receptors appears to arise from several gene families or subfamilies rather than from DNA rearrangement. (12 Dec 1998) |
| receptors, opioid | Cell membrane proteins that bind opioids and trigger intracellular changes which influence the behaviour of cells. The endogenous ligands for opioid receptors in mammals include three families of peptides, the enkephalins, endorphins, and dynorphins. The receptor classes include mu, delta, and kappa receptors. Sigma receptors bind several psychoactive substances, including certain opioids, but their endogenous ligands are not known. (12 Dec 1998) |
| receptors, opioid, delta | A class of opioid receptors recognised by its pharmacological profile. Delta opioid receptors bind endorphins and enkephalins with approximately equal affinity and have less affinity for dynorphins. (12 Dec 1998) |
| receptors, opioid, kappa | A class of opioid receptors recognised by its pharmacological profile. Kappa opioid receptors bind dynorphins with a higher affinity than endorphins which are themselves preferred to enkephalins. (12 Dec 1998) |
| receptors, opioid, mu | A class of opioid receptors recognised by its pharmacological profile. Mu opioid receptors bind, in decreasing order of affinity, endorphins, dynorphins, met-enkephalin, and leu-enkephalin. They have also been shown to be molecular receptors for morphine. (12 Dec 1998) |
| receptors, oxytocin | Cell surface proteins that bind oxytocin with high affinity and trigger intracellular changes which influence the behaviour of cells. Oxytocin receptors in the uterus and the mammary glands mediate the hormone's stimulation of contraction and milk ejection. The presence of oxytocin and oxytocin receptors in neurons of the brain probably reflects an additional role as a neurotransmitter. (12 Dec 1998) |
| receptors, pancreatic hormone | Cell surface proteins that bind pancreatic hormones with high affinity and trigger intracellular changes which influence the behaviour of cells. These include receptors for glucagon (secreted by alpha cells), insulin (secreted by beta cells), somatostatin (secreted by delta cells), and pancreatic peptide (secreted by pp cells). Some of these hormones and receptors also support neurotransmission. (12 Dec 1998) |
| receptors, parathyroid hormone | Cell surface proteins that bind parathyroid hormone with high affinity and trigger intracellular changes which influence the behaviour of cells. Parathyroid hormone receptors on bone, kidney, and gastrointestinal cells mediate the hormone's role in calcium and phosphate homeostasis. (12 Dec 1998) |
| receptors, peptide | Cell surface receptors that bind peptide messengers with high affinity and regulate intracellular signals which influence the behaviour of cells. (12 Dec 1998) |
| receptors, phencyclidine | Specific sites or molecular structures on cell membranes or in cells with which phencyclidine reacts or to which it binds to elicit the specific response of the cell to phencyclidine. Studies have demonstrated the presence of multiple receptor sites for pcp. These are the pcp/sigma site, which binds both pcp and psychotomimetic opiates but not certain antipsychotics, and the pcp site, which selectively binds pcp analogs. (12 Dec 1998) |
| receptors, pituitary hormone | Cell surface proteins that bind pituitary hormones with high affinity and trigger intracellular changes influencing the behaviour of cells. Since many pituitary hormones are also released by neurons as neurotransmitters, these receptors are also found in the nervous system. (12 Dec 1998) |
| receptors, pituitary hormone-regulating hormone | Cell surface receptors that bind the hypothalamic hormones regulating pituitary cell differentiation, proliferation, and hormone synthesis and release, including the pituitary-releasing and release-inhibiting hormones. The pituitary hormone-regulating hormones are also released by cells other than hypothalamic neurons, and their receptors also occur on non-pituitary cells, especially brain neurons, where their role is less well understood. Receptors for dopamine, which is a prolactin release-inhibiting hormone as well as a common neurotransmitter, are not included here. (12 Dec 1998) |
| receptors, platelet-derived growth factor | Specific molecular sites or structures on cell membranes that react with platelet-derived growth factor, its analogs, or antagonists, to elicit or to inhibit the specific response of the cell to this factor. Pdgf binds with different affinities and specificities to two structurally related receptors, the alpha-receptor and the beta-receptor. Both of these receptors are transmembrane proteins with an intracellular, ligand-stimulatable protein kinase domain. (12 Dec 1998) |
| receptors, polymeric immunoglobulin | Specialised fc receptors (receptors, fc) for polymeric immunoglobulins, which mediate transcytosis of polymeric IgA and IgM into external secretions. They are found on the surfaces of epithelial cells and hepatocytes. After binding to IgA, the receptor-ligand complex undergoes endocytosis, transport by vesicle, and secretion into the lumen by exocytosis. Before release, the part of the receptor (secretory component) that is bound to IgA is proteolytically cleaved from its transmembrane tail. (12 Dec 1998) |