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.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1727-1735 |
| Number of pages | 9 |
| Journal | European Journal of Neuroscience |
| Volume | 17 |
| Issue number | 9 |
| DOIs | |
| State | Published - May 2003 |
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Keywords
- Circadian rhythms
- Light response
- Patch-clamp electrophysiology
- Photoentrainment
- Retinal ganglion cells
- Trp channels
ASJC Scopus subject areas
- Neuroscience(all)
Cite this
Intrinsic light responses of retinal ganglion cells projecting to the circadian system. / Warren, Erin J.; Allen, Charles; Brown, R. Lane; Robinson, David.
In: European Journal of Neuroscience, Vol. 17, No. 9, 05.2003, p. 1727-1735.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Intrinsic light responses of retinal ganglion cells projecting to the circadian system
AU - Warren, Erin J.
AU - Allen, Charles
AU - Brown, R. Lane
AU - Robinson, David
PY - 2003/5
Y1 - 2003/5
N2 - 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.
AB - 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.
KW - Circadian rhythms
KW - Light response
KW - Patch-clamp electrophysiology
KW - Photoentrainment
KW - Retinal ganglion cells
KW - Trp channels
UR - http://www.scopus.com/inward/record.url?scp=0038392663&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0038392663&partnerID=8YFLogxK
U2 - 10.1046/j.1460-9568.2003.02594.x
DO - 10.1046/j.1460-9568.2003.02594.x
M3 - Article
VL - 17
SP - 1727
EP - 1735
JO - European Journal of Neuroscience
JF - European Journal of Neuroscience
SN - 0953-816X
IS - 9
ER -