Search results for "acetylcholine receptor"
showing 10 items of 263 documents
Facilitatory and inhibitory muscarine receptors on the rat phrenic nerve: effects of pirenzepine and dicyclomine
1988
Neuronal transmitter stores of the rat phrenic nerve were labelled by an incubation with [3H]choline. Release of [3H]acetylcholine was elicited either by a short (100 pulses, 5 Hz) or by a long (1500 pulses, 5 or 25 Hz) period of electrical nerve stimulation. Pirenzepine and dicyclomine enhanced transmitter release evoked by the short stimulation period. Both antagonists reduced transmitter release evoked by the long stimulation period. Pirenzepine reduced transmitter release at low concentrations (1 nmol/l) whereas a higher concentration was necessary for the enhancing effect; the opposite pattern was found for dicyclomine. A low concentration of oxotremorine (10 nmol/l) enhanced and a hig…
Role of the M3 Muscarinic Acetylcholine Receptor Subtype in Murine Ophthalmic Arteries After Endothelial Removal
2014
We tested the hypothesis that the M3 muscarinic acetylcholine receptor subtype mediates cholinergic responses in murine ophthalmic arteries after endothelial removal.Muscarinic receptor gene expression was determined in ophthalmic arteries with intact and with removed endothelium using real-time PCR. To examine the role of the M3 receptor in mediating vascular responses, ophthalmic arteries from M3 receptor-deficient mice (M3R(-/-)) and respective wild-type controls were studied in vitro. Functional studies were performed in nonpreconstricted arteries with either intact or removed endothelium using video microscopy.In endothelium-intact ophthalmic arteries, mRNA for all five muscarinic rece…
Functional relevance of presynaptic muscarinic autoreceptors.
1993
Pre- and postsynaptic muscarinic receptors have been characterized in the isolated trachea and ileal circular muscle of the guinea pig. The muscarinic autoreceptors mediating inhibition of acetylcholine release in the circular muscle belong to the M1 subtype, whereas those inhibiting acetylcholine release in the trachea are M2 or M4 receptors. In both tissues the postsynaptic muscarinic receptors are M3 receptors. Blockade of the autoreceptors by selective M1 and M2/M4 receptor antagonists leads to facilitation of cholinergic neurotransmission.
gamma-Aminobutyric acid and cholinergic transmission in the guinea-pig ileum.
1983
1. The effects of GABA on release of acetylcholine and on contractility of the smooth muscle were studied in the myenteric plexus-longitudinal muscle preparation of the guinea pig. Acetylcholine was determined as radiolabelled transmitter from strips preloaded with 3H-choline. 2. GABA (1–300 μM) caused an increase in resting tension of smooth muscle as well as an increase in release of acetylcholine that was considerably reduced by tetrodotoxin. The facilitation by GABA of acetylcholine release exhibited a marked tachyphylaxis. The increase in muscle tension was clearly related to the increase in acetylcholine release. Muscimol (0.1–10 μM) also enhanced the release of acetylcholine. The eff…
Characterization of prejunctional muscarinic autoreceptors in the guinea-pig trachea
1991
1. The effects of ten muscarinic antagonists on electrically evoked [3H]-acetylcholine release and muscle contraction were compared in an epithelium-free preparation of the guinea-pig trachea that had been preincubated with [3H]-choline. 2. The M3-selective antagonists UH-AH 37, 4-diphenyl-acetoxy-N-piperidine methobromide and para-fluorohexahydrosiladiphenidol were more potent in reducing the contractile response than in facilitating the evoked [3H]-acetylcholine release. Hexahydrosiladiphenidol did not discriminate between pre- and postjunctional effects. The rank order of the postjunctional potencies of the ten antagonists as well as the postjunctional pA2 values obtained for hexahydrosi…
Inhibitory and excitatory muscarinic receptors modulating the release of acetylcholine from the postganglionic parasympathetic neuron of the chicken …
1992
The effects of muscarinic receptor antagonists on ACh release were studied in the absence or presence of cholinesterase (ChE) inhibition using the isolated perfused chicken heart. Presynaptic inhibitory muscarinic autoreceptor were characterized by determining the potency of various antagonists to enhance [3H]-ACh release evoked by field stimulation (3 Hz, 1 min). The order of potencies was: (±)-telenzepine > atropine > 4-DAMP > silahexocyclium > pirenzepine > hexahydro-siladifenidol > AF-DX 116. The comparison with known pA2 values for M1-, M2- and M3-receptors revealed that the presynaptic autoreceptor meets the criteria of an M1-receptor. Basal, not electrically evoked overflow of unlabe…
Two types of neuronal muscarine receptors modulating acetylcholine release from guinea-pig myenteric plexus
1985
Longitudinal muscle strips of the guinea-pig ileum were incubated with [3H]choline and the effects of muscarinic agonists on smooth muscle contraction and on spontaneous and electrically-evoked outflow of tritium were studied. Muscarine and pilocarpine concentration-dependently increased both muscle contraction and spontaneous outflow of [3H]ACh, and inhibited the electrically-evoked outflow of [3H]ACh. The increase in spontaneous outflow was prevented by tetrodotoxin and scopolamine, but not by hexamethonium. Oxotremorine (1-100 microM) did not increase the spontaneous outflow of tritium. Pirenzepine in concentrations of 10 and 100 nM hardly affected the muscle contractions induced by pilo…
Release of [3H]acetylcholine from the isolated rat or guinea-pig trachea evoked by preganglionic nerve stimulation; a comparison with transmural stim…
1991
Basal and stimulated outflow of radioactive acetylcholine, phosphorylcholine and choline from rat and guinea-pig isolated tracheae were measured by reverse phase HPLC followed by liquid-scintillation-spectrometry. Tracheae were stimulated either by an electrical field (transmural stimulation) or by a local stimulation of the innervating parasympathetic nerves (preganglionic stimulation). Epithelium was removed in most experiments, as the epithelium inhibits acetylcholine release. The basal tritium efflux (1,600 dpm/3min) from rat isolated tracheae incubated with [3H]choline consisted of 56% [3H]phosphorylcholine and 38% [3H]choline. Preganglionic stimulation (15 Hz, 1,200 pulses) caused a 2…
Immunochemical characterization of anti-acetylcholine receptor antibodies in primary biliary cirrhosis
1988
Although the presence of anti-mitochondrial antibodies is the main characteristic of primary biliary cirrhosis (PBC), other autoantibodies have been described in this disease. This study employs immunoblot methods to test whether the sera of PBC patients also contain antibodies directed against nicotinic acetylcholine receptors (AChR). We show that the majority of patients' sera indeed react with AChR just as sera of myasthenic patients do. In contrast, however, these anti-AChR antibodies do not lead to significant clinical symptoms of myasthenia. In all cases studied, PBC sera recognized a protein with the molecular weight of the alpha-chain of acetylcholine receptor (40 kDa). In addition,…
Muscarinic Receptor Activation Increases Efflux of Choline from Isolated Heart and Rat Cortex in Vivo. Interactions with Forskolin and IBMX
1986
Muscarinic receptor activation modulates functions of the heart and neurotransmission in the peripheral and central nervous system. Moreover, muscarinic agonists produce changes in the metabolism of, for example, heart tissue, such as inhibition of beta-adrenoceptor-mediated cAMP accumulation, glycogenolysis and lipase activation.