And acetylcholine

In 1966, the name was proposed (5) for receptors blocked by the at that time known antihistamines. It was also speculated that the other actions of histamine were likely to be mediated by other histamine receptors. The existence of the H2 receptor was accepted in 1972 (6) and the receptor was recognized in rat brain in 1983 (7). receptors in the brain appear to be involved in the feedback control of both histamine synthesis and release, whereas release of various other neurotransmitters, eg, serotinin (5-HT), dopamine, noradrenaline, and acetylcholine, is also modulated (8) (see Neuroregulators). 

Potassium [7440-09-7] K, is the third, element ia the aLkaU metal series. The name designation for the element is derived from potash, a potassium mineral the symbol from the German name kalium, which comes from the Arabic qili, a plant. The ashes of these plants al qili) were the historical source of potash for preparing fertilisers (qv) or gun powder. Potassium ions, essential to plants and animals, play a key role in carbohydrate metaboHsm in plants. In animals, potassium ions promote glycolysis, Hpolysis, tissue respiration, and the synthesis of proteins (qv) and acetylcholine. Potassium ions are also beheved to function in regulating blood pressure. 

Naturally occurring quaternary ammonium compounds have been reviewed (179). Many types of aliphatic, heterocycHc, and aromatic derived quaternary ammonium compounds are produced both in plants and invertebrates. Examples include thiamine (vitamin B ) (4) (see Vitamins) choline (qv) [62-49-7] (5) and acetylcholine (6). These have numerous biochemical functions. Several quaternaries are precursors for active metaboUtes. 

Lazareno, S., and Birdsall, N. J. M. (1995). Detection, quantitation, and verification of allosteric interactions of agents with labeled and unlabeled ligands at G protein-coupled receptors Interactions of strychnine and acetylcholine at muscarinic receptors. Mol. Pharmacol. 48 362-378. 

The histamine H2-receptor (359 amino acids) is best known for its effect on gastric acid secretion. Histamine H2-receptor activation, in conjunction with gastrin and acetylcholine from the vagus, potently stimulate acid secretion from parietal cells. High concentrations of histamine are also present in cardiac tissues and can stimulate positive chronotropic and inotropic effects via H2-receptor stimulation and activation of adenylyl... 

Chromaffin granules, platelet dense core vesicles, and synaptic vesicles accumulate ATP. ATP uptake has been demonstrated using chromaffin granules and synaptic vesicles and the process appears to depend on A(.lh+. It has generally been assumed that ATP is costored only with monoamines and acetylcholine, as an anion to balance to cationic charge of those transmitters. However, the extent of ATP storage and release by different neuronal populations remains unknown, and the proteins responsible for ATP uptake by secretory vesicles have not been identified. 

To achieve their different effects NTs are not only released from different neurons to act on different receptors but their biochemistry is different. While the mechanism of their release may be similar (Chapter 4) their turnover varies. Most NTs are synthesised from precursors in the axon terminals, stored in vesicles and released by arriving action potentials. Some are subsequently broken down extracellularly, e.g. acetylcholine by cholinesterase, but many, like the amino acids, are taken back into the nerve where they are incorporated into biochemical pathways that may modify their structure initially but ultimately ensure a maintained NT level. Such processes are ideally suited to the fast transmission effected by the amino acids and acetylcholine in some cases (nicotinic), and complements the anatomical features of their neurons and the recepter mechanisms they activate. Further, to ensure the maintenance of function in vital pathways, glutamate and GABA are stored in very high concentrations (10 pmol/mg) just as ACh is at the neuromuscular junction. 

The cortical cup has been used for many years to monitor changes in transmitter release induced by physiological and pharmacological stimuli (Fig. 4.5). In the past, it was used most commonly to study release of amino acids and acetylcholine. More recently, it has... 

Flentge, F, Venema, K, Koch, T and Korf, J (1997) An enz5mie-reactor for electrochemical monitoring of choline and acetylcholine. Applications in high-performance liquid chromatography, brain tissue, microdialysis and cerebral fluid. Annal. Biochem. 204 305-311. 

Lodge, D. Anis, N.A. and Burton, N.R. Effects of optical isomers of ketamine on excitation of cat and rat spinal neurons by amino acids and acetylcholine. Neurosci Lett 29 282-286, 1982. 

FDA approved intraocular injections include mio-tics, viscoelastics, and viscoadherents and an antiviral agent for intravitreal injection. The approved intraocular miotics, carbachol (Miostat ) and acetylcholine (Miochol ), are injected into the anterior chamber at the end of cataract surgery to constrict the pupil and allow the iris to cover the implanted intraocular lens. Carbachol is formulated in a BSS vehicle in sterile water for injection at a physiological pH... 

Herbal preparations may be prepared by freezedrying or air-drying. Fresh, freeze-dried leaves of nettle were shown to be effective for symptomatic relief in allergic rhinitis. The active components in nettle, histamine and acetylcholine, became ineffective when the... 

Birdsall NJ, Farries T, Gharagozloo P, Kobayashi S, Lazareno S, Sugimoto M. Subtype-selective positive cooperative interactions between brucine analogs and acetylcholine at muscarinic receptors functional studies. Mol Pharmacol 1999 55 778-786. 

The primary mechanism used by cholinergic synapses is enzymatic degradation. Acetylcholinesterase hydrolyzes acetylcholine to its components choline and acetate it is one of the fastest acting enzymes in the body and acetylcholine removal occurs in less than 1 msec. The most important mechanism for removal of norepinephrine from the neuroeffector junction is the reuptake of this neurotransmitter into the sympathetic neuron that released it. Norepinephrine may then be metabolized intraneuronally by monoamine oxidase (MAO). The circulating catecholamines — epinephrine and norepinephrine — are inactivated by catechol-O-methyltransferase (COMT) in the liver. 

Some arousal-related neurotransmitters, including noradrenaline, serotonin, and acetylcholine, feed back to inhibit POA sleep-active neurons. This aspect of the system has been reviewed previously (McGinty Szymusiak, 2000 Saper et al., 2001). Therefore, once sleep-active neurons are activated, arousal-related neurons are inhibited, and inhibitory control of sleep-active neurons by arousal systems is reduced. In this way, sleep onset is facilitated. That is, the mutually inhibitory systems can switch more quickly from wake to sleep, and back. These mutually inhibitory interactions also promote stability of both waking and sleep. 

Jouvet, M. (1972). The role of monoamines and acetylcholine-containing neurons in the regulation of the sleep-waking cycle. Ergeb. Physiol. 64, 166-307. 

Pontine cholinergic agonists and acetylcholine esterase inhibitors... 

Velazquez-Moctezuma, J., Shiromani, P. J. 8i Gillin, J. C. (1990b). Acetylcholine and acetylcholine receptor subtypes in REM sleep generation. Prog. Brain Res. 84,... 

Ghosh P. K., Hrdina P. D., Ling G. M. (1976). Effects of REMS deprivation on striatal dopamine and acetylcholine in rats. Pharmacol. Biochem. Behav. 4(4), 401-5. 

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