Journal article
Intrinsic light responses of retinal ganglion cells projecting to the circadian system
The European journal of neuroscience, Vol.17(9), pp.1727-1735
05/2003
Handle:
https://hdl.handle.net/2376/115800
PMCID: PMC2435209
PMID: 12752771
Abstract
In mammals, light entrainment of the circadian clock, located in the suprachiasmatic nuclei (SCN), requires retinal input. Traditional rod and cone photoreceptors, however, are not required. Instead, the SCN-projecting retinal ganglion cells (RGCs) function as autonomous photoreceptors and exhibit light responses independent of rod- and cone-driven input. Using whole-cell patch-clamp recording techniques, we have investigated the morphological and electrophysiological properties of this unique class of RGCs. Although SCN-projecting RGCs resemble Type III cells in form, they display strikingly different physiological properties from these neurons. First, in response to the injection of a sustained depolarizing current, SCN-projecting cells fired in a transient fashion, in contrast to most RGCs which fired robust trains of action potentials. Second, in response to light, SCN-projecting RGCs exhibited an intensity-dependent transient depolarization in the absence of rod and cone input. This depolarization reached a peak within 5 s and generated increased spiking activity before decaying to a plateau. Voltage-clamp recordings were used to characterize the light-activated conductance which generated this depolarization. In response to varying light intensities, SCN-projecting RGCs exhibited a graded transient inward current which peaked within 5 s and decayed to a plateau. The voltage dependence of the light-activated current was obtained by subtracting currents elicited by a voltage ramp before and during illumination. The light-activated current displayed both inward and outward rectification and was largely unaffected by substitution of extracellular Na+ with choline. In both respects, the intrinsic light-activated current observed in SCN-projecting RGCs resembles currents carried by ion channels of the transient receptor potential (trp) family, which are known to mediate the light response of invertebrate photoreceptors.
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Details
- Title
- Intrinsic light responses of retinal ganglion cells projecting to the circadian system
- Creators
- Erin J Warren - Department of Physiology and Pharmacology, L334, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USACharles N AllenR Lane BrownDavid W Robinson
- Publication Details
- The European journal of neuroscience, Vol.17(9), pp.1727-1735
- Academic Unit
- Integrative Physiology and Neuroscience, Department of
- Publisher
- France
- Grant note
- R21 MH063364-01 / NIMH NIH HHS MH 63364 / NIMH NIH HHS R01 MH067094 / NIMH NIH HHS T32 NS007466 / NINDS NIH HHS R21 MH063364-02 / NIMH NIH HHS NS07466 / NINDS NIH HHS R01 MH067094-01A1 / NIMH NIH HHS
- Identifiers
- 99900547851901842
- Language
- English
- Resource Type
- Journal article