Identification of αRGC subtypes and characterization of their oscillatory properties. (A) Light-evoked response and morphology of an OFF αRGC. Membrane potential change to light stimulation in an OFF αRGC (left). Whole-mount view of an OFF αRGC (center). The white rectangle indicates an ROI. Side view of the stacked NB and ChAT images in the ROI. A plot of labeling intensity versus IPL depth indicates that dendritic arborization of the OFF αRGC (NB: green) is relative to the position of ChAT bands (magenta) in the ROI. The OFF αRGC dendrites stratify in the OFF sublamina. Whole-mount view of the stacked NB-stained OFF αRGC image (green) and SMI-32 images (cyan) (right). The white arrowhead indicates colocalization of the OFF αRGC soma with the SMI-32 signal. (B) Light response and morphology of an ON αRGC. No obvious light-evoked response was observed in an ON αRGC (left). Morphological analysis in an ON αRGC (center). The ON αRGC dendrites stratify in the ON sublamina. Whole-mount view of the stacked ON αRGC image (green) and SMI-32 images (cyan) (right). Scale bar: 50 µm. (C) RGC oscillations in the Trpm1 KO mouse retina. Membrane potential trace from an OFF αRGC under the current-clamp condition (left). Spike events (top) and voltage trace (bottom). Autocorrelogram (center) is calculated from the spike events (left). The PSD (right) is derived from the autocorrelogram (center). A clear peak was detected at 8.5 Hz. (D) The frequency of oscillations in OFF and ON αRGCs (OFF αRGCs: 8.5 ± 0.3 Hz, n = 22 cells from nine mice; ON αRGCs: 8.1 ± 0.6 Hz, n = 5 cells from five mice; P = 0.55). (E) Phase relationship of oscillatory firing between αRGC pairs. Top: Membrane potential changes (bottom) and spike events (top) obtained from a pair of OFF (blue) and ON (orange) αRGCs (left), and from a pair of OFF (blue) and OFF (black) αRGCs (right). Bottom: CCRs calculated from the spike events. (F) Phase difference of αRGC oscillations: different-type: 167.3 ± 7.6°, n = 3 cell pairs from three mice; same-type: 10.0 ± 5.0°, n = 3 cell pairs from two mice; P = 1.89 × 10−5. (G) Schematic diagram of the rod pathway including an AII AC. Excitatory (magenta) and inhibitory (cyan) synapses, as well as gap junction (▬), are illustrated. (H) Synaptic currents (bottom) measured at different holding potentials (top) from an OFF αRGC (left) and an ON αRGC (right) under the whole-cell voltage-clamp condition. (I) Amplitude of synaptic currents at different holding potentials (OFF αRGCs: n = 23 cells from 19 mice; ON αRGCs: n = 18 cells from 16 mice). (J) Reversal potentials of oscillatory synaptic currents in OFF and ON αRGCs (OFF αRGCs: −56.4 ± 1.8 mV, n = 23 cells from 19 mice; ON αRGCs: −1.3 ± 2.8 mV, n = 18 cells from 16 mice; P = 8.03 × 10−20). Data are presented as the mean ± SEM. An unpaired t test was used for statistical analysis. n.s., not significant; ***P < 0.001. ROI, region of interest.
Figure 1.

Identification of αRGC subtypes and characterization of their oscillatory properties. (A) Light-evoked response and morphology of an OFF αRGC. Membrane potential change to light stimulation in an OFF αRGC (left). Whole-mount view of an OFF αRGC (center). The white rectangle indicates an ROI. Side view of the stacked NB and ChAT images in the ROI. A plot of labeling intensity versus IPL depth indicates that dendritic arborization of the OFF αRGC (NB: green) is relative to the position of ChAT bands (magenta) in the ROI. The OFF αRGC dendrites stratify in the OFF sublamina. Whole-mount view of the stacked NB-stained OFF αRGC image (green) and SMI-32 images (cyan) (right). The white arrowhead indicates colocalization of the OFF αRGC soma with the SMI-32 signal. (B) Light response and morphology of an ON αRGC. No obvious light-evoked response was observed in an ON αRGC (left). Morphological analysis in an ON αRGC (center). The ON αRGC dendrites stratify in the ON sublamina. Whole-mount view of the stacked ON αRGC image (green) and SMI-32 images (cyan) (right). Scale bar: 50 µm. (C) RGC oscillations in the Trpm1 KO mouse retina. Membrane potential trace from an OFF αRGC under the current-clamp condition (left). Spike events (top) and voltage trace (bottom). Autocorrelogram (center) is calculated from the spike events (left). The PSD (right) is derived from the autocorrelogram (center). A clear peak was detected at 8.5 Hz. (D) The frequency of oscillations in OFF and ON αRGCs (OFF αRGCs: 8.5 ± 0.3 Hz, n = 22 cells from nine mice; ON αRGCs: 8.1 ± 0.6 Hz, n = 5 cells from five mice; P = 0.55). (E) Phase relationship of oscillatory firing between αRGC pairs. Top: Membrane potential changes (bottom) and spike events (top) obtained from a pair of OFF (blue) and ON (orange) αRGCs (left), and from a pair of OFF (blue) and OFF (black) αRGCs (right). Bottom: CCRs calculated from the spike events. (F) Phase difference of αRGC oscillations: different-type: 167.3 ± 7.6°, n = 3 cell pairs from three mice; same-type: 10.0 ± 5.0°, n = 3 cell pairs from two mice; P = 1.89 × 10−5. (G) Schematic diagram of the rod pathway including an AII AC. Excitatory (magenta) and inhibitory (cyan) synapses, as well as gap junction (▬), are illustrated. (H) Synaptic currents (bottom) measured at different holding potentials (top) from an OFF αRGC (left) and an ON αRGC (right) under the whole-cell voltage-clamp condition. (I) Amplitude of synaptic currents at different holding potentials (OFF αRGCs: n = 23 cells from 19 mice; ON αRGCs: n = 18 cells from 16 mice). (J) Reversal potentials of oscillatory synaptic currents in OFF and ON αRGCs (OFF αRGCs: −56.4 ± 1.8 mV, n = 23 cells from 19 mice; ON αRGCs: −1.3 ± 2.8 mV, n = 18 cells from 16 mice; P = 8.03 × 10−20). Data are presented as the mean ± SEM. An unpaired t test was used for statistical analysis. n.s., not significant; ***P < 0.001. ROI, region of interest.

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