Intrinsic and extrinsic light responses in melanopsin-expressing ganglion cells during mouse development. J Neurophysiol 2008 Jul;100(1):371-84
Date
05/16/2008Pubmed ID
18480363Pubmed Central ID
PMC2493479DOI
10.1152/jn.00062.2008Scopus ID
2-s2.0-51349093447 (requires institutional sign-in at Scopus site) 143 CitationsAbstract
Melanopsin (Opn4) is a photopigment found in a subset of retinal ganglion cells (RGCs) that project to various brain areas. These neurons are intrinsically photosensitive (ipRGCs) and are implicated in nonimage-forming responses to environmental light such as the pupillary light reflex and circadian entrainment. Recent evidence indicates that ipRGCs respond to light at birth, but questions remain as to whether and when they undergo significant functional changes. We used bacterial artificial chromosome transgenesis to engineer a mouse line in which enhanced green fluorescent protein (EGFP) is expressed under the control of the melanopsin promoter. Double immunolabeling for EGFP and melanopsin demonstrates their colocalization in ganglion cells of mutant mouse retinas. Electrophysiological recordings of ipRGCs in neonatal mice (postnatal day 0 [P0] to P7) demonstrated that these cells responded to light with small and sluggish depolarization. However, starting at P11 we observed ipRGCs that responded to light with a larger and faster onset (<1 s) and offset (<1 s) depolarization. These faster, larger depolarizations were observed in most ipRGCs by early adult ages. However, on application of a cocktail of synaptic blockers, we found that all cells responded to light with slow onset (>2.5 s) and offset (>10 s) depolarization, revealing the intrinsic, melanopsin-mediated light responses. The extrinsic, cone/rod influence on ipRGCs correlates with their extensive dendritic stratification in the inner plexiform layer. Collectively, these results demonstrate that ipRGCs make use of melanopsin for phototransduction before eye opening and that these cells further integrate signals derived from the outer retina as the retina matures.
Author List
Schmidt TM, Taniguchi K, Kofuji PAuthor
Kenichiro Taniguchi PhD Associate Professor in the Cell Biology Neurobiology and Anatomy department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Action PotentialsAge Factors
Animals
Animals, Newborn
Chromosomes, Artificial, Bacterial
Dose-Response Relationship, Radiation
Gene Expression Regulation, Developmental
Green Fluorescent Proteins
Light
Mice
Mice, Transgenic
Patch-Clamp Techniques
Photic Stimulation
Reaction Time
Retina
Retinal Ganglion Cells
Rod Opsins
