Document Detail

Evidence for a photosensitive region in the caudal mesencephalon of the turtle brain.
MedLine Citation:
PMID:  9588779     Owner:  NLM     Status:  MEDLINE    
Using an in vitro brainstem-cerebellum preparation from the turtle Chrysemys picta, burst discharge was recorded from the abducens nerve when light was directed on the brainstem. This burst discharge likely represents a neural correlate of the eye-blink reflex. Increasing the intensity of the light stimulus reduced the response latency from a duration of many seconds to approximately 1-2 s. No response was recorded when the light source was covered. The response was present when infrared light was blocked, and it could only be produced when the light spectra contained wavelengths below approximately 550 nm. Lesion experiments reveal that the photosensitive area is located caudal to the trochlear nerve and rostral to the trigeminal nerve. Single-unit microelectrode recordings demonstrate that this region is tonically active in the dark and that activity is suppressed by light. Pharmacological results show that the light response is blocked by application of compounds that act as serotonergic antagonists, and that antagonists of noradrenergic receptors (alpha or beta) either have no effect or their actions are variable. Taken together, these data suggest that an isthmo-optic-like area in the turtle brain is photosensitive to direct light and activates neural circuits that control eye movements.
C W Anderson; J Keifer
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Experimental brain research     Volume:  119     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  1998 Apr 
Date Detail:
Created Date:  1998-06-26     Completed Date:  1998-06-26     Revised Date:  2013-12-13    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  453-9     Citation Subset:  IM    
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MeSH Terms
Adrenergic Antagonists / pharmacology
Extracellular Space / drug effects,  physiology
Mesencephalon / anatomy & histology,  drug effects,  physiology*
Photic Stimulation
Photoreceptor Cells / drug effects,  physiology*
Serotonin Antagonists / pharmacology
Turtles / physiology*
Grant Support
Reg. No./Substance:
0/Adrenergic Antagonists; 0/Serotonin Antagonists

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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