| receptors, muscarinic | One of the two major classes of cholinergic receptors. Muscarinic receptors were originally defined by their preference for muscarine over nicotine. There are several subtypes (usually m1, m2, m3...) that are characterised by their cellular actions, pharmacology, and molecular biology. (12 Dec 1998) |
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| muscarinic | 1. Having a muscarine-like action, i.e., producing effects that resemble postganglionic parasympathetic stimulation. 2. An agent that stimulates the postganglionic parasympathetic receptor. See: muscarine, nicotinic. (05 Mar 2000) |
| muscarinic acetylcholine receptor | Distinct from the nicotinic ACh receptor in having no intrinsic ion channel, the receptor is formed from one protein chain with 7 transmembrane regions. The receptors produce their effect via activation of GTP-binding proteins. (18 Nov 1997) |
| muscarinic agonist | Drugs that bind to and activate muscarinic cholinergic receptors (receptors, muscarinic). Muscarinic agonists are most commonly used when it is desirable to increase smooth muscle tone, especially in the GI tract, urinary bladder and the eye. They may also be used to reduce heart rate. (12 Dec 1998) |
| muscarinic antagonist | Drugs which bind with muscarinic cholinergic receptors but do not activate them, thus preventing access to acetylcholine; examples include atropine, scopolamine, propantheline, and pirenzepine. (05 Mar 2000) |
| muscarinic antagonists | Drugs that bind to but do not activate muscarinic cholinergic receptors (receptors, muscarinic), thereby blocking the actions of endogenous acetycholine or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system. Antagonists that discriminate among the various muscarinic receptor subtypes and might allow better control of peripheral and central actions are under development. (12 Dec 1998) |
| muscarinic receptor kinase | <enzyme> Phosphorylates muscarinic acetylcholine receptors and beta-adrenergic receptors Registry number: EC 2.7.- Synonym: muscarinic acetylcholine receptor kinase, machr kinase (26 Jun 1999) |
| muscarinic receptors | Membrane-bound proteins whose extracellular domain contains a recognition site for acetylcholine (ACh); combination of Ach with the receptor 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 receptors are to be distinguished from nicotinic receptors. (05 Mar 2000) |
| axoaxonic synapse | The synaptic junction between an axon terminal of one neuron and either the initial axon segment or an axon terminal of another nerve cell. (05 Mar 2000) |
| axodendritic synapse | The synaptic contact between an axon terminal of one nerve cell and a dendrite of another nerve cell. (05 Mar 2000) |
| axosomatic synapse | The synaptic junction of an axon terminal of one nerve cell to the cell body of another nerve cell. Synonym: pericorpuscular synapse. (05 Mar 2000) |
| rectifying synapse | <physiology> An electrical synapse at which current flow can only occur in one direction. (18 Nov 1997) |
| pericorpuscular synapse | The synaptic junction of an axon terminal of one nerve cell to the cell body of another nerve cell. Synonym: pericorpuscular synapse. (05 Mar 2000) |
| chemical synapse | <physiology> A nerve nerve or nerve muscle junction where the signal is transmitted by release from one membrane of a chemical transmitter that binds to a receptor in the second membrane. Importantly, signals only pass in one direction. (18 Nov 1997) |
| ribbon synapse | <biology, physiology> Ultrastructurally distinct type of synapse found in a variety of sensory receptor cells such as retinal photoreceptor cells, cochlear hair cells and vestibular organ receptors, as well as in a nonsensory neuron, the retinal bipolar cell. Unlike most neurons, these cells do not use regenerative action potentials but release transmitter in response to small graded potential changes. Ribbon synapses have different exocytotic machinery from conventional synapses in containing dense bars or ribbons anchored to the presynaptic membrane covered with a layer of synaptic vesices. The ribbons have been proposed to shuttle synaptic vesicles to exocytotic sites. (23 Aug 1998) |