receptor (re-sep´tor, tor)
1. A structural protein molecule on the cell surface or within the cytoplasm that binds to a specific factor, such as a hormone, antigen, or neurotransmitter. 2. C. Sherrington's term for any one of the various sensory nerve endings in the skin, deep tissues, viscera, and special sense organs.ceptor; [L. receiver, fr. recipio, to receive]
adrenergic r.'s reactive components of effector tissues, most of which are innervated by adrenergic postganglionic fibers of the sympathetic nervous system. Such r.'s can be activated by norepinephrine and/or epinephrine and by various adrenergic drugs; r. activation results in a change in effector tissue function, such as contraction of arteriolar muscles or relaxation of bronchial muscles; adrenergic r.'s are divided into a-r.'s and beta-r.'s, on the basis of their response to various adrenergic activating and blocking agents.adrenoceptor, adrenoreceptors;
a-adrenergic r.'s adrenergic r.'s in effector tissues capable of selective activation and blockade by drugs; conceptually derived from the ability of certain agents, such as phenoxybenzamine, to block only some adrenergic r.'s and of other agents, such as methoxamine, to activate only the same adrenergic r.'s. Such r.'s are designated as a-receptors. Their activation results in physiological responses such as increased peripheral vascular resistance, mydriasis, and contraction of pilomotor muscles.
beta-adrenergic r.'s adrenergic r.'s in effector tissues capable of selective activation and blockade by drugs; conceptually derived from the ability of certain agents, such as propranolol, to block only some adrenergic r.'s and of other agents, such as isoproterenol, to activate only the same adrenergic r.'s. Such r.'s are designated as beta-receptors. Their activation results in physiological responses such as increases in cardiac rate and force of contraction (beta1), and relaxation of bronchial and vascular smooth muscle (beta2).
AMPA r. a type of glutamate r. that participates in excitatory neurotransmission and also binds a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and acts as a cation channel.quisqualate r;
ANP r.'s cell surface r.'s for atrial natriuretic peptide that have a single transmembrane spanning element; these have integral kinase and guanylate cyclase domains.
ANP clearance r.'s cell surface proteins that bind atrial natriuretic peptide and ANP fragments without initiating biological action.
asialoglycoprotein r. a surface r. found in hepatocytes that binds galactose-terminal glycoproteins; thus, this r. removes those proteins from circulation and they are in turn acted upon by hepatocyte lysosomes.
B cell antigen r.'s in the primary immune response immunoglobulin D and monomeric immunoglobulin M are the B cell antigen r.'s. On memory B cells, other immunoglobulin molecules can serve as antigen r.'s.
cholinergic r.'s chemical sites in effector cells or at synapses through which acetylcholine exerts its action.
Fc r. r.'s present on a variety of cells for the Fc fragment of immunoglobulins. These r.'s recognize immunoglobulins of the IgG and IgE class.
kainate r. a type of glutamate r. that participates in excitatory neurotransmission and also binds kainate and acts as a cation channel; injection of kainate causes death of neurons but preserves glial cells and axons.
laminin r. a r. found in many cell types that binds laminin and has a role in cell attachment and neurite outgrowth.
L-AP4 r. a type of glutamate receptor that also binds a particular synthetic agonist and acts as a cation channel.
low-density lipoprotein r.'s r.'s on the surface of cells, especially liver cells, which bind to low density lipoprotein and promote clearance of LDL from the plasma.
mannose-6-phosphate r.'s (MPR) r.'s in Golgi apparatus to which newly synthesized proteins that are destined to enter lysosomes bind.
metabotropic r. a type of r. that is linked to intracellular production of 1,2-diacylglycerol and inositol 1,4,5-trisphosphate. [metabolism + G. trope, turning, inclination, + -ic]
muscarinic r.'s membrane-bound proteins whose extracellular domain contains a recognition site for acetylcholine (ACh); combination of Ach with the r. initiates a physiologic change (slowing of heart rate, increased glandular secretory activity and stimulation of smooth muscle contractions); changes are observed after treatment with the mushroom alkaloid, muscarine. Muscarinic r.'s are to be distinguished from nicotinic r.'s.
nicotinic r.'s a class of cholinergic r.'s on skeletal muscle cells that are linked to ion channels in the cell membrane.
nicotinic cholinergic r. a class of r.'s responsive to acetylcholine that also are activated by nicotine; ganglionic (including the adrenal medulla) and neuromuscular r.'s. Two classes exist: nicotinic- neuronal and nicotinic-muscular.
NMDA r. a type of glutamate r. that participates in excitatory neurotransmission and also binds N-methyl-d-aspartate; may be particularly involved in the cell damage observed in individuals with Huntington's disease.
opiate r.'s regions of the brain which have the capacity to bind morphine; some, along the aqueduct of Sylvius and in the center median, are in areas related to pain, but others, as in the striatum, are not related.
quisqualate r. AMPA r
sensory r.'s peripheral endings of afferent neurons.
stretch r.'s r.'s that are sensitive to elongation, especially those in Golgi tendon organs and muscle spindles, but also those found in visceral organs such as the stomach, small intestine, and urinary bladder; these r.'s have the function of detecting elongation, and this distinguishes them from baroreceptors, which actually are activated by stretching of the wall of the blood vessel but whose function is to elicit central reflex mechanism reducing the arterial blood pressure.
T cell antigen r.'s r.'s present on T cells that interact with both processed antigen and major histocompatibility antigens simultaneously.
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