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Muscarinic receptor agonists and antagonists: effects on ocular function.
MedLine Citation:
PMID:  22222703     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
Muscarinic agonists act mainly via muscarinic M(3) cholinoceptors to cause contraction of the iris sphincter, ciliary muscle and trabecular meshwork as well as increase outflow facility of aqueous humour. In the iris dilator, the effect of muscarinic agonists is species dependent but is predominantly relaxation via muscarinic M(3) receptors. In the conjunctiva, muscarinic agonists stimulate goblet cell secretion which contributes to the protective tear film. Muscarinic M(2) and M(3) receptors appear mainly involved. In the lens muscarinic agonists act via muscarinic M(1) receptors to produce depolarization and increase [Ca(2+)](i). All five subtypes of muscarinic receptor are present in the retina. In the developing retina, acetylcholine appears to limit purinergic stimulation of retinal development and decrease cell proliferation. In the adult retina acetylcholine and other muscarinic agonists may have complex effects, for example, enhancing light-evoked neuronal firing in transient ON retinal ganglion cells and inhibiting firing in OFF retinal ganglion cells. In the lacrimal gland, muscarinic agonists activate M(3) receptors on secretory globular acinar cells to stimulate tear secretion and also cause contraction of myoepithelial cells. In Sjögren's syndrome, antibodies to the muscarinic M(3) receptor disrupt normal gland function leading to xerophthalmia although the mechanism of action of the antibody is still not clear. Atropine and pirenzepine are useful in limiting the development of myopia in children probably by an action on muscarinic receptors in the sclera, although many other muscarinic receptor antagonists are not effective.
Authors:
Frederick Mitchelson
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Handbook of experimental pharmacology     Volume:  208     ISSN:  0171-2004     ISO Abbreviation:  Handb Exp Pharmacol     Publication Date:  2012  
Date Detail:
Created Date:  2012-01-06     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7902231     Medline TA:  Handb Exp Pharmacol     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  263-98     Citation Subset:  IM    
Affiliation:
Department of Pharmacology, University of Melbourne, Melbourne, VIC, 3010, Australia, fjmitc@unimelb.edu.au.
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