Cholinergic fibres

In addition to these problems there is no evidence of reduced NGF in AzD although levels and receptor number are lower in the nucleus basalis. In fact the levels of NGF were found to be increased in the cortex and hippocampus (Scott el al. 1995) and while this could just be due to fewer cholinergic fibres to transport it away from the cortex it does suggest its synthesis is normal and possibly even increased. At least it throws doubt on the value of augmenting NGF as a therapy for AzD. 

Q4 The ganglionic transmitter of both divisions of the autonomic nervous system is acetylcholine. The major postganglionic neurotransmitter of the sympathetic nervous system is norepinephrine (noradrenaline), but a small number of structures are innervated by sympathetic, cholinergic fibres. These fibres release acetylcholine and the structures innervated include the sweat glands and blood vessels supplying skeletal muscle. In the parasympathetic system the postganglionic neurotransmitter is acetylcholine. 

Since the somata of the great majority of cortical cholinergic fibres are located subcortically (Hebb et al., 1963 Krnjevic and Silver, 1965), stimulation of the surface will activate only the terminals orthodromically, while stimulation of the reticular formation activates the cholinergic fibres trans-synaptically (Szerb, 1967). Atropine approximately doubled the ACh release due to surface stimulation but increased 4-5 times ACh release resulting from reticular formation stimulation (Fig. 1). These results can be interpreted as follows for the full effect of atropine on ACh output it is necessary that the somata of cholinergic neurones be synaptically activated either... 

By blocking a recurrent inhibitory loop which governs the activity of ascending cholinergic fibres. This can only be shown in vivo. 

Krnjevic, K. and Silver. A. (1965) A histochemical study of cholinergic fibres in the cerebral cortex. J. Anat. (Lond.), 99,711-759. 

Hyoscamine acts on tissue cells innervated by post-ganglionic cholinergic fibres of the parasympathetic nervous system it is antimuscarinic and a parasympathetic depressant. 

Fig. 2.20 Efferent pathways into bulb showing (a) cholinergic (ACh) fibres projecting to MOB from basal forebrain nuclei. AON = ant. olfactory nucleus, OT = olfactory tract, DB = diagonal band nuc. (from Davis et al., 1978). (b) Nor-Adrenalin input to AOB, via MFB pathway from brain stem centres (nuclei A1-2, A6) (from Keveme, 1971).

The cholinergic neurons are immediately distal to dopaminergic fibres in the caudate nucleus in brain. They are excitatory and in parkinsonism, there is a degeneration of inhibitory dopaminergic neurons and thus, there is increased cholinergic activity (preponderance of cholinergic system) which results in the symptoms of parkinsonism. 

The vagus nerve is a major connection between central and peripheral components. It contains both afferent (80%) and efferent (20%) pathways from and to the upper GIT. These include both cholinergic and non-cholinergic nerve fibres the non-cholinergic neurones may have serotonin as transmitter. Two types of vagal afferent receptors are involved in the emetic response (1) mechanoreceptors, iocated in the muscular wall of the distal stomach and proximal duodenum, which are activated by distension or contraction of the gut wall and (2) chemoreceptors located in the gut mucosa of the upper small bowel. These monitor the... 

Day, T.A., Chen, G.Z., Miller, C., Tian, M., Bennett, J.L. and Pax, R.A. (1996) Cholinergic inhibition of muscle fibres isolated from Schistosoma mansoni (Trematoda Digenea). Parasitology 113, 55-61. 

Chole- Relating to the biliary system, cholestasis The failure of the normal bile flow to the intestine, causing cholestatic jaundice, cholinergic Nerve fibres that release ACETYLCHOLINE, cholinesterases Enzymes that hydrolyse choline esters, especially ACETYLCHOLINE of which there are two main forms acetylcholinesterase ( true cholinesterase ) is specific for acetylcholine, rapid in this action, and has a discrete distribution being especially located near cholinergic nerve terminals (and in erythrocytes) butyrylcholinesterase ( pseudo cholinesterase) is less selective and is able to hydrolyse some drugs (e.g. SUCCINYLCHOLINE CHLORIDE). Many drugs are known that inhibit the action of these enzymes. See anticholinesterases. chromatin A protein found in the nucleus which stains with basic dyes. It is used in the study of the behaviour of... 

RT-PCR from rat ileal tissue showed a protein band corresponding to that for VRl mRNA from rat brain (Anavi-Goffer et al. 2002). Cholinergic VRl receptorpositive fibres in the ter tiary plexus were found to co-express calretinin, substance P and synapsin 1. These findings support results from functional studies indicating that VRl activation is related to ACh release from motoneurons (Mang et al. 

A very substantial contribution to the identification of the cholinergic nerve elements in the hippocampal region was the demonstration by Shute and Lewis (1961) and Lewis and Shute (1967) that AChE disappears from the neuropil of this region after transection of the fimbria (Fig. 5). Corresponding results were obtained for ChAc (Lewis et al., 1967). The few perikarya that stained for AChE, retained their staining after the transection. AChE and ChAc accumulated in fibres in fimbria... 

Although somewhat controversial and incomplete, the pharmacological results support the notion that the ChAc-containing system of septo-hippocampal fibres is cholinergic. 

A study of the distribution, in the mammalian central nervous system, of the various substances discussed in this review reveals that none—except y-aminobutyric acid which has general metabolic as well as humoral functions—is as widespread as acetylcholine and there is no general tendency for fibres deficient in acetylcholine to contain correspondingly large amounts of any of the other substances. This is an important point, since the non-cholinergic excitatory transmitter should be found in at least a number of acetylcholine-free nerve tracts. Instead, it appears that some areas of the nervous system contain a multiplicity of humoral substances while others have none at all. 

Evidence that acetylcholine is a chemical mediator of synaptic transmission elsewhere in the central nervous system is circumstantial but convincing. Acetylcholine is the transmitter substance from motor nerves, preganglionic autonomic fibres and the postganglionic fibres of the parasympathetic system to their respective effector cells. In all these fibres, the activity of choline acetyltransferase (choline acetylase), the enzyme responsible for the synthesis of acetylcholine, is high. Conversely, its activity is negligibly low in sensory nerve fibres and transmission from these fibres is demonstrably non-cholinergic in nature . It is reasonable, therefore, to... 

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