Document Detail

Intrinsically photosensitive retinal ganglion cells are the primary but not exclusive circuit for light aversion.
MedLine Citation:
PMID:  23078956     Owner:  NLM     Status:  Publisher    
Photoallodynia (photophobia) occurs when normal levels of light cause pain ranging from uncomfortable to debilitating. The only current treatment for photoallodynia is light avoidance. The first step to understanding the mechanisms of photoallodynia is to develop reliable animal behavioral tests of light aversion and identify the photoreceptors required to initiate this response. A reliable light/dark box behavioral assay was developed that measures light aversion independently from anxiety, allowing direct testing of one endophenotype of photoallodynia in mice. Mice lacking intrinsically photosensitive retinal ganglion cells (ipRGCs) exhibit reduced aversion to bright light, suggesting these cells are the primary circuit for light aversion. Mice treated with exogenous μ opiate receptor agonists exhibited dramatically enhanced light aversion, which was not dependent on ipRGCs, suggesting an alternative pathway for light is engaged. Morphine enhances retinal electrophysiological responses to light but only at low levels. This suggests that for the dramatic light aversion observed, opiates also sensitize central brain regions of photoallodynia. Taken together, our results suggest that light aversion has at least two dissociable mechanisms by which light causes specific allodynia behaviors: a primary ipRGC-based circuit, and a secondary ipRGC-independent circuit that is unmasked by morphine sensitization. These models will be useful in delineating upstream light sensory pathways and downstream avoidance pathways that apply to photoallodynia.
Anna Matynia; Sachin Parikh; Bryan Chen; Paul Kim; David S McNeill; Steven Nusinowitz; Christopher Evans; Michael B Gorin
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-15
Journal Detail:
Title:  Experimental eye research     Volume:  -     ISSN:  1096-0007     ISO Abbreviation:  Exp. Eye Res.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370707     Medline TA:  Exp Eye Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Published by Elsevier Ltd.
Department of Ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine, UCLA, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA. Electronic address:
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