Acetylcholine overview

Kawashima, K., Fujii, T. (2008). Basic and clinical aspects of nonneuronal acetylcholine overview of non-neuronal cholinergic systems and their biological significance. J. Pharmacol. Sci. 106 167-73. 

There are numerous transmitter substances. They include the amino acids glutamate, GABA and glycine acetylcholine the monoamines dopamine, noradrenaline and serotonin the neuropeptides ATP and NO. Many neurones use not a single transmitter but two or even more, a phenomenon called cotransmission. Chemical synaptic transmission hence is diversified. The basic steps, however, are similar across all neurones, irrespective of their transmitter, with the exception of NO transmitter production and vesicular storage transmitter release postsynaptic receptor activation and transmitter inactivation. Figure 1 shows an overview. Nitrergic transmission, i.e. transmission by NO, differs from transmission by other transmitters and is not covered in this essay. 

After an overview of neurotransmitter systems and function and a consideration of which substances can be classified as neurotransmitters, section A deals with their release, effects on neuronal excitability and receptor interaction. The synaptic physiology and pharmacology and possible brain function of each neurotransmitter is then covered in some detail (section B). Special attention is given to acetylcholine, glutamate, GABA, noradrenaline, dopamine, 5-hydroxytryptamine and the peptides but the purines, histamine, steroids and nitric oxide are not forgotten and there is a brief overview of appropriate basic pharmacology. 

Combi R, Dalpra L, Tenchini ML, Ferini-Strambi L (2004) Autosomal dominant nocturnal frontal lobe epilepsy A critical overview, J Neurol 251 923-934 Connolly J, Boulter J, Heinemann SF (1992) Alpha 4-2 beta 2 and other nicotinic acetylcholine receptor subtypes as targets of psychoactive and addictive drugs, Br J Pharmacol 105 657-666 Conti-Tronconi BM, Dunn SM, Barnard EA, DoUy JO, Lai FA, Ray N, Raftery MA (1985) Brain and muscle nicotinic acetylcholine receptors are different but homologous proteins, Proc Natl Acad Sci U S A 82 5208-5212... 

The recent developments in the determination of acetylcholine and choline, the advantages and the disadvantages of a variety of analytical methods used in the analysis, were reviewed and discussed by Maruyama et al. [7]. Hanin published an overview for the methods used for the analysis and measurement of acetylcholine [8], Shimada et al. presented a review, including the applications of some reactors in the analysis of choline and acetylcholine. The immobilized enzyme reactors were used for detection systems in high performance liquid chromatography [9],... 

Karube and Yokoyama presented an overview on the developments in the biosensor technology [60]. The overview describes the use of micromachining fabrication techniques for the construction of detection units for FIA, electrochemical flow cells and chemiluminescence detectors. Acetylcholine microsensors using carbon fiber electrodes and glutamate microsensors for neuroscience were discussed. 

Aizawa presented an overview on the principles and applications of the electrochemical and optical biosensors [61]. The current development in the biocatalytic and bioaffinity bensensor and the applications of these sensors were given. The optical enzyme sensor for acetylcholine was based on use of an optical pH fiber with thin polyaniline film. 

Figure 4.10. Overview of nerve impulse transmission in chemical synapses. The action potential in the presynaptic nerve cell induces release of the nemotransmitter (e.g., acetylcholine) into the synaptic cleft. The transmitter binds to its receptor, e.g. the nicotinic acetylcholine receptor (NAR). The NAR is a hgand-gated channel it will open and become permeable to both and Na. This will move the membrane potential toward the average of the two respective equilibrium potentials however, in the process, the firing level of adjacent voltage-gated sodium charmels will be exceeded, and a full action potential will be triggered (inset).

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