Neuroscience
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Cellular and Molecular Neurobiology 11. Acetylcholine Neurotransmission |
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Neuroscience
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Cellular and Molecular Neurobiology 11. Acetylcholine Neurotransmission |
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Behavior and Clinical |
The rapid nature of the synaptic transmission mediated by the nicotinic receptor is consistent with its role at the NMJ and in the ganglion of the ANS. Little is known about the role of the nicotinic receptor role in CNS behavior. Clearly, nicotine stimulation is related in some manner to reinforcement, as indicated by the prevalence of nicotine addiction among humans.
Muscarinic receptors, in contrast, are important mediators of behavior in the CNS. One example is their role in modulating motor control circuits in the basal ganglia. A second example is their participation in learning and memory. The latter is inferred from two types of observations: 1) muscarinic antagonists are amnesic agents, and 2) deterioration of the cholinergic innervation of the neocortex is associated with memory loss in Alzheimer’s disease.
Alzheimer's disease: A disease in which a marked deterioration occurs in the CNS, the hallmark of which is a progressive dementia. One of the characteristics of this disease is a marked decrease in ACh concentrations in the cerebral cortex and caudate nucleus.
Myasthenia gravis: A disease of the neuromuscular junction in which the receptors for ACh are destroyed through the actions of the patient's own antibodies.
Cholinergic Pharmacology: Numerous drugs are used clinically to interact with the cholinergic systems. Table II summarizes the major uses for cholinergic drugs.
Table II
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Drug |
Action |
Clinical use |
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Atropine (and other anticholinergics)
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Blocks muscarinic receptors
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Relaxes muscle in the eye causing the pupil to dilate. Used when the eye is inflamed and during eye examinations. |
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Slows the activity of the stomach and intestinal track and reduces acid secretion. Therefore, used for stomach cramps, diarrhea, diverticulitis, pancreatitis, bed wetting, motion sickness. |
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There has been some indication of this drug for Parkinson’s disease. |
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Scopolamine |
Blocks CNS muscarinic receptors |
Used topically to prevent dizziness, nausea and other aspects of motion sickness. |
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Amantadine (Symmetrel) |
Blocks muscarinic receptors |
Antidyskinetics used to treat Parkinson’s disease and the dyskinesia associated with antipsychotic drugs |
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Bethanechol |
Mimics ACh |
Used to treat urinary retention, and stimulate movement of intestinal tract. |
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Tacrine (Cognex) |
Blocks ACh breakdown |
Treat Alzheimer’s disease |
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Eserine or physostigmine |
Blocks ACh breakdown |
Reduces pressure in the eye and is used to treat glaucoma |
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Used to diagnose and treat myasthesia gravis |
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Test Your Knowledge |
| 12. Which of the following is effective in increasing the level of acetylcholine in the synapse or neuromuscular junction? (Note: There is more than one correct answer.) |
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Contact the author(s) at: nba_course@uth.tmc.edu
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The University of Texas Health Science Center at Houston
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