Cholinergic systems function

Cory-Slechta DA. 1995a. Relationships between lead-induced learning impairments and changes in dopaminergic, cholinergic, and glutamatergic neurotransmitter system functions. Annu Rev Pharmacol Toxicol 35 391-415. 

Jones, B. (1993). The organization of central cholinergic systems and their functional importance in sleep-waking states. In Cholinergic Function and Dysfunction. Progress in Brain Research, ed. A. Cuello. Amsterdam Elsevier. 

Acetylcholine Mescaline, in micromolar concentrations, decreases the release of acetylcholine at the neuromuscular junction, with subsequent effects on end-plate potentials and motor function (Ghansah et al. 1993). Whether or not any similar effect occurs on central cholinergic systems has not been investigated. 

Some functional neuroimaging studies have examined the effects of scopolamine in cognitive tasks. Although scopolamine inhibits increases in cerebral blood flow to somatosensory stimulation, it does not inhibit the neural response (Ogawa et al. 1994). Thus, cholinergic systems may be involved in coordination of cerebral blood flow increases to neural activation. Subjects performing an attentional auditory discrimination... 

There is also evidence that the density of muscarinic receptors is increased in limbic regions of depressed patients who have committed suicide. If it is assumed that such a change reflects an increased activity of the cholinergic system, it could help to explain the reduced noradrenergic function as there is both clinical and experimental evidence to suggest that increased central cholinergic activity can precipitate depression and reduce noradrenergic activity. 

The central cholinergic system has been implicated in the pathogenesis of affective disorder and in memory function, which is frequently found to be malfunctioning in depressed patients. The memory deficit elicited by chronic ECT in both patients and animals may be related to the decreased density and function of central muscarinic receptors, but it should be emphasized that the changes reported in cholinergic function are small and their relevance to the clinical situation remains to be established. 

Lesions of the basal forebrain cholinergic system using a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) result in impaired attentional, but not mnemonic, function in rats (Muir et al., 1995) and monkeys (Voytko et al., 1994), an effect which has been confirmed using more selective IgG-saporin lesions (Baxter et al., 1995 Everitt 8c Robbins, 1997). 

Electromicroscopy of the presynaptic terminals of injured cortex treated with NGF shows a slight hypertrophy with an increase in synaptic differentiations of the membrane. The synaptic changes are larger and more pronounced in the cerebral cortex than in the cholinergic system. Biochemical changes have also been observed that indicate an improvement in the presynaptic functions of the cholinergic projections in the hippocampus and cerebral cortex. 

Muir JL, Dunnett SB, Robbins TW, et al Attentional functions of the forebrain cholinergic systems effects of intraventricular hemichohnium, physostigmine, basal forebrain lesions and intracortical grafts on a multiple-choice serial reaction time task. Exp Brain Res 89 611-622, 1992 Mukherjee S Mechanisms of the antimanic effect of electroconvulsive therapy. Convulsive Therapy 5 227-243, 1989... 

The body contains two main classes of cholinesterase acetylcholinesterase (EC 3.1.1.7) and butyrylcholinesterase (EC 3.1.1.8).27 The former, sometimes referred to as true cholinesterase, Is mainly a tissue enzyme and Is found mainly In such tissues as the synapses of the cholinergic system It Is also found In other tissues, such as erythrocytes, where Its function Is uncertain. The latter, referred to as pseudocholinesterase, Is a soluble enzyme that is synthesized In the liver and circulates in the plasma-... 

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