Search results for "choline"
showing 10 items of 1138 documents
Mucosa-dependent muscarinic liberation of prostaglandins from rat isolated trachea.
1995
1. The present study examined whether cholinoceptor stimulation modulates the release of arachidonic acid-derived mediators from rat isolate tracheae. 2. Tracheae were preincubated with [3H]-arachidonic acid and the outflow of 3H-compounds was determined. Acetylcholine and the muscarinic agonist, carbachol but not nicotine, increased the rate of tritium outflow maximally by about 30%. The M3 receptor-preferring antagonist rho-fluoro-hexahydrosiladiphenidol was more effective than pirenzepine and methoctramine in antagonizing the effect of acetylcholine. 3. High performance liquid chromatography analysis (methanol gradient) of the released 3H-compounds showed that one peak, co-eluting with […
Pre- and postsynaptic effects of muscarinic agonists in the guinea-pig ileum
1980
The effects of several muscarinic agonists on smooth muscle (postsynaptic effect) and on acetylcholine release (presynaptic effect) were compared in the longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum. 1. For release experiments the acetylcholine stores of the preparation were labelled with 3H-choline. Electrical field stimulation in the absence of a cholinesterase inhibitor caused an outflow of tritium that reflected release of 3H-acetylcholine. The agonists oxotremorine, arecaidinepropargylester, methylfurmethide, muscarine, carbachol, arecoline and pilocarpine inhibited the stimulation-induced outflow in a concentration-dependent manner. At the highest concentrat…
Compensatory mechanisms enhance hippocampal acetylcholine release in transgenic mice expressing human acetylcholinesterase
2001
Central cholinergic neurotransmission was studied in learning-impaired transgenic mice expressing human acetylcholinesterase (hAChE-Tg). Total catalytic activity of AChE was approximately twofold higher in synaptosomes from hippocampus, striatum and cortex of hAChE-Tg mice as compared with controls (FVB/N mice). Extracellular acetylcholine (ACh) levels in the hippocampus, monitored by microdialysis in the absence or presence of 10(-8)-10(-3) M neostigmine in the perfusion fluid, were indistinguishable in freely moving control and hAChE-Tg mice. Muscarinic receptor functions were unchanged as indicated by similar effects of scopolamine on ACh release and of carbachol on inositol phosphate fo…
The release of choline from phospholipids mediated by beta-adrenoceptor activation in isolated hearts.
1986
The resting efflux of choline into the perfusate (Tyrode's solution) of isolated hearts was equal to the rate, at which choline was liberated from phospholipid degradation (Lindmar et al. 1986). Infusion of isoprenaline (2 X 10(-7) mol/l), forskolin (1-3 X 10(-6) mol/l) or 3-isobutyl-1-methylxanthine (IBMX; 3 X 10(-4) mol/l) for 40 min markedly enhanced the efflux of choline. The increase was linear during the experimental period and, in the case of isoprenaline, was blocked by 3 X 10(-7) mol/l atenolol. In the guinea-pig heart, IBMX at a threshold concentration of 10(-4) mol/l shifted the concentration-response curve for the effect of forskolin on the efflux of choline to the left by one l…
Alterations on AChE Activity of the Fish Anguilla anguilla as Response to Herbicide-Contaminated Water
2000
Abstract The inhibition of both total and specific acetylcholinesterase activities was measured in the whole eyes of the yellow eel Anguilla anguilla after exposure to the carbamate thiobencarb. In vivo assays were conducted under a constant flow-through system of thiobencarb-contaminated water (1/60 LC50 96 h=0.22 ppm for 96 h) followed by a recovery period in clean water (192 h more). The results indicated a measurable level of AChE activity on eyes of control eels, which resulted in a sensitive indicator of the presence of thiobencarb in the water. The pesticide induced significant inhibitory effects on AChE activity ranging from 35% in total AChE activity to 75% in specific AChE activit…
Effects of Norepinephrine and Cardiotrophin-1 on Phospholipase D Activity and Incorporation of Myristic Acid Into Phosphatidylcholine in Rat Heart
2004
The present study is part of a project on phospholipase D (PLD) in cardiac hypertrophy and analyzed effects on PLD activity of two growth stimuli, norepinephrine (NE) and cardiotrophin-1 (CT-1), in incubated rat heart. Phosphatidylcholine (PC) was labeled by 3H-myristic acid. PLD produced 3H-phosphatidylethanol (3H-PEth) from 3H-PC in the presence of ethanol and maintained a basal formation of 3H-PEth. Short-term and long-term exposure to NE for 2 or 13 h, respectively, enhanced the formation of 3H-PEth, which was blocked by prazosin. Long-term pretreatment with NE or CT-1 increased the incorporation of 3H-myristic acid into PC, which was blocked by atenolol. When the 3H-PEth formation was …
Cholinergic–Adrenergic Presynaptic Interactions in the Heart and Characterization of the Receptors Involved
1991
ABSTRACT The rabbit perfused atria preparation with the extrinsic sympathetic and vagus innervation intact has been used to study the mutual interactions between the two branches of the autonomic nervous system by measuring the respective transmitter overflow rates upon electrical stimulation. Using this method the stimuli exciting vagus and sympathetic nerves can be applied at selected time intervals which provides an advantage over the common method of field stimulation where all kinds of neurons are stimulated simultaneously. In the absence of drugs, presynaptic interactions resulting in a decreased noradrenaline overflow occurred when the vagal stimuli preceded the sympathetic ones by 3…
The Homeostasis of Brain Choline
1993
The interest in the homeostasis of brain choline is reinforced by the role of choline as immediate precursor of acetylcholine, phosphatidylcholine and other phospholipids in the brain. In order to obtain a comprehensive view of the mochanisms of homeostasis it appeared necessary to elucidate the negative arteriovenous difference of choline across the brain (net release), a phenomenon that has been known for 20 years and is present in mammals and in man. This finding prompted an intense search for a de novo synthesis of choline in the brain. We detected in anaesthetized rats a reversal of the net release into a net uptake (positive arterio-venous difference), when the plasma level of choline…
Tissue Differences in the Effect of Atropine on the Evoked Release of Acetylcholine
1979
The effect of atropine on the release of acetylcholine (ACh) from different peripheral parasympathetically innervated tissues was investigated. My enteric plexus The longitudinal muscle-myenteric plexus preparation of the guinea-pig was incubated in eserinecontaining Tyrode solution. The ACh release evoked by high K+ (45 or 108 μ) or by the nicotinic drug dimethylphenylpiperazinium (DMPP) (10 pM) was increased by atropine (0.1–10 μ) in a concentration-dependent fashion. Muscarinic agonists (oxotremorine; propargylester of arecaidine) prevented the facilitatory effect of atropine on ACh release. These results suggest that the ACh release from the myenteric plexus is regulated via presynaptic…
Chapter 21 Modulation of acetylcholine release by nitric oxide
1996
Publisher Summary This chapter reviews the studies in which the effects of endogenous and exogenous nitric oxide (NO) on the release of acetylcholine were investigated. As tools for the involvement of endogenous NO, the effects of NO synthase inhibitors on release of acetylcholine were studied. The cholinergic neurons are tonically stimulated by endogenous NO. On the other hand, NO synthase inhibitors fail to change either basal or electrically evoked acetylcholine release from slices of rat hippocampus and striatum. Endogenous and exogenous NO increase basal acetylcholine release from central and peripheral cholinergic neurons. The effect is tetrodotoxin sensitive and calcium-dependent, th…