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Shigang He

Publications and source records attributed to Shigang He.

11 recordsLinked to original sources
PubMed2006

ON direction-selective ganglion cells in the mouse retina.

Two types of ganglion cells (RGCs) compute motion direction in the retina: the ON-OFF direction-selective ganglion cells (DSGCs) and the ON DSGCs. The ON DSGCs are much less studied mostly due to the low encounter rate. In this study, we investigated the physiology, dendritic morphology and synaptic inputs of the ON DSGCs in the mouse retina. When a visual stimulus moved back and forth in the preferred-null axis, we found that the ON DSGCs exhibited a larger EPSC when the visual stimulus moved in the preferred direction and a larger IPSC in the opposite, or null direction, similar to what has been found in ON-OFF DSGCs. This similar synaptic input pattern is in contrast to other well-known differences, namely: profile of velocity sensitivity, distribution of preferred directions, and different central projection of the axons. Immunohistochemical staining showed that the dendrites of ON DSGCs exhibited tight cofasciculation with the cholinergic plexus. These findings suggest that cholinergic amacrine cells may play an important role in generating direction selectivity in the ON DSGCs, and that the mechanism for coding motion direction is probably similar for the two types of DSGCs in the retina.

Animals↗
PubMed2006

Lateral components in the cone terminals of the rabbit retina: horizontal cell origin and glutamate receptor expression.

We examined the identities of horizontal cell (HC) lateral components in cone terminals and the expression of glutamate receptors on the tips of HC dendrites. We injected A-type horizontal cells (AHCs) with neurobiotin and demonstrated that neurobiotin labeled completely all AHCs within a patch of retina. We converted neurobiotin by using diaminobenzidine and considered labeled processes to be from AHCs and unlabeled processes to be from B-type horizontal cells (BHCs). Three possible combinations of HC dendrites could exist in cone pedicles: both lateral components originating from AHCs, both from BHCs, or one from an AHC and the other from a BHC. EM observations revealed that a majority of cone terminals contained about equal numbers of lateral components originating from each of the two types of HCs and that each of the three possible combinations was present in equal numbers. Localization of different types of glutamate receptors on HC dendritic tips showed that 55% of AHC dendritic tips expressed AMPA receptors and 30% expressed kainate receptors, whereas, in the case of BHCs, 22% of dendritic tips expressed AMPA receptors and 33% expressed kainate receptors. This study suggests that cone photoreceptors feed the light signal equally into networks of AHCs and BHCs and that differential expression of AMPA/kainate receptors by different HCs could account for different functions.

Animals↗
PubMed2004

Identification of ON-OFF direction-selective ganglion cells in the mouse retina.

We identified the ON-OFF direction-selective ganglion cells (DSGCs) in the mouse retina and characterized their physiological, morphological and pharmacological properties. These cells showed transient responses to the onset and termination of a stationary flashing spot, and strong directional selectivity to a moving rectangle. Application of various pharmacological reagents demonstrated that the ON-OFF DSGCs in the mouse retina utilize a similar array of transmitters and receptors to compute motion direction to their counterparts in the rabbit retina. Voltage clamp recording showed that ON-OFF DSGCs in the mouse retina receive a larger inhibitory input when the stimulus is moving in the null direction and a larger excitatory input when the stimulus is moving in the preferred direction. Finally, intracellular infusion of neurobiotin revealed a bistratified dendritic field with recursive dendrites forming loop-like structures, previously classified as RG(D2) by morphology. Overall, the ON-OFF DSGCs in the mouse retina exhibit almost identical properties to their counterparts in the rabbit retina, indicating that the mechanisms for computing motion direction are conserved from mouse to rabbit, and probably also to higher mammals. This first detailed characterization of ON-OFF DSGCs in the mouse retina provides fundamental information for further study of maturation and regulation of the neuronal circuitry underlying computation of direction.

Action Potentials↗
PubMed2004

Dendritic relationship between starburst amacrine cells and direction-selective ganglion cells in the rabbit retina.

We investigated the dendritic relationship between starburst amacrine cells (SAs) and morphologically and physiologically characterized ON and ON-OFF direction-selective ganglion cells (DSGCs) in the rabbit retina. ON and ON-OFF DSGCs were found to exhibit tight dendritic cofasciculation with the SA plexus, visualized by immunolabelling of the vesicular acetylcholine transporter (VAChT). The degree of cofasciculation of both types of DSGC dendrites and SA plexus was found to be significant, unlike the relationship between non-DS cells and the SA plexus, which was close to chance distribution. No difference in the degree of cofasciculation in different regions of the DS dendritic field was observed. Individual SAs intracellularly injected both on the 'preferred' and 'null' side of the DSGCs showed the same degree of cofasciculation with the DSGCs. Therefore, the computation of motion direction is unlikely to result from apparent asymmetry in geometric proximity between SAs and DSGCs. Highly selective synaptic connections between SAs and DSGCs are necessary.

Amacrine Cells↗
PubMed2004

Localization of dopamine D1-receptor to A-type horizontal cells in the rabbit retina by single cell RT-PCR.

Dopamine is an important neurotransmitter regulating light-dark adaptation in the retina. The effect of dopamine is widespread and dependent on the localization of its receptors. We performed single cell RT-PCR on A-type horizontal cells visually selected from dissociated rabbit retinal neurons. Dopamine D1-receptor mRNA was positively identified. Subsequent sequencing of the fragment showed 82% homology with rat D1 receptor and 87% homology with human D1 receptor. This study supported previous observations that dopamine regulated A-type horizontal cell coupling via D1 receptors at the level of transcription.

Adaptation, Ocular↗
PubMed2004

Development of the mouse retina: emerging morphological diversity of the ganglion cells.

The time course and regulatory mechanisms of dendritic development are subjects of intense interest. We approached these problems by investigating dendritic morphology of retinal ganglion cells (RGCs) at four early postnatal stages. The RGCs develop from a diffusely stratified and poorly differentiated group at birth (P0), to 16 distinct, morphologically well-defined subtypes before eye opening (P13). Even before bipolar cells make synaptic contacts with the RGCs (P8), most adultlike RGC subtypes are already present. Similar to previous studies in other mammalian species, our results indicate that the initiation of the RGC morphological maturation is independent of light stimulation and of formation of glutamatergic synapses. This study narrowed down the window of RGCs morphological maturation and highlighted a few early postnatal events as potential factors controlling the developmental process. Because mouse is the most popular mammalian model for genetic manipulation, this study provided a foundation for further exploring regulatory mechanisms of RGC dendritic development.

Animals↗
PubMed2003

Spontaneous waves in the ventricular zone of developing mammalian retina.

Spontaneous rhythmic waves in the developing mammalian retina are thought to propagate among differentiated neurons in the inner retina (IR) and play an important role in activity-dependent visual development. Here we report a new form of rhythmic Ca(2+) wave in the ventricular zone (VZ) of the developing rabbit retina. Ca(2+) imaging from two-photon optical sections near the ventricular surface of the whole-mount retina showed rhythmic Ca(2+) transients propagating laterally as waves. The VZ waves had a distinctively slow Ca(2+) dynamics (lasting approximately 20 s) but shared a similar frequency and propagation speed with the IR waves. Simultaneous Ca(2+) imaging in VZ and multi-electrode array recording in the ganglion cell layer (GCL) revealed close spatiotemporal correlation between spontaneous VZ and IR waves, suggesting a common source of initiation and/or regulation of the two waves. Pharmacological studies further showed that all drugs that blocked IR waves also blocked VZ waves. However, the muscarinic antagonist atropine selectively blocked VZ but not IR waves at this developmental stage, indicating that IR waves were not dependent on VZ waves, but VZ waves likely relied on the initiation of IR waves. Eliciting IR waves with puffs of nicotinic or non-N-methyl-d-aspartate agonists in GCL produced atropine-sensitive waves in the VZ, demonstrating a unique, retrograde signaling pathway from IR to VZ. Thus differentiated neurons in the IR use spontaneous, rhythmic waves to send both forward signals to the central visual targets and retrograde messages to the developing cells in the VZ.

Animals↗
PubMed2003

Seeing more clearly: recent advances in understanding retinal circuitry.

Among 10 breakthroughs that Science announced at the end of 2002 was the discovery of a photosensing (melanopsin-containing) retinal ganglion cell (RGC) and its role in entraining the circadian clock. This breakthrough exemplifies the ultimate goal of neuroscience: to understand the nervous system from molecules to behavior. Light-sensing RGCs constitute one of a dozen discrete RGC populations coding various aspects of visual scenes by virtue of their unique morphology, physiology, and coverage of the retina. Interestingly, the function of the melanopsin-containing RGCs in entraining the circadian clock need not involve much retinal processing, making it the simplest form of processing in the retina. This review focuses on recent advances in our understanding of retinal circuitry, visual processing, and retinal development demonstrated by innovative experimental techniques. It also discusses the advantages of using the retina as a model system to address some of the key questions in neuroscience.

Animals↗
PubMed2002

Large-scale morphological survey of mouse retinal ganglion cells.

Five hundred twenty ganglion cells in an isolated whole-mount preparation of the mouse retina were labeled using the "DiOlistic" method (Gan et al. [2000] Neuron 27:219-225) and were classified according to their morphological properties. Tungsten particles coated with a lipophilic dye (DiI) were propelled into the whole-mount retina using a gene gun. When a dye-coated particle contacted the cell membrane, the entire cell was labeled. The ganglion cells were classified into four groups based on their soma size, dendritic field size, and pattern and level of stratification. Broadly monostratified cells were classified into three groups: RG(A) cells (large soma, large dendritic field), RG(B) cells (small to medium-sized soma, small to medium-sized dendritic field), and RG(C) cells (small to medium-sized size soma, medium-sized to large dendritic field). Bistratified cells were classified as RG(D). This study represents the most complete morphological classification of mouse retinal ganglion cells available to date and provides a foundation for further understanding of the correlation of physiology and morphology and ganglion cell function with genetically manipulated animals.

Animals↗
PubMedDate not supplied

Large-scale morophological survey of rat retinal ganglion cells.

Ganglion cells in an isolated wholemount preparation of the rat retina were labeled using the "DiOlistic" labeling method (Gan et al., 2000) and were classified according to their morphological properties. Tungsten particles coated with a lipophilic dye (DiI) were propelled into the wholemount retina using a gene gun. When a dye-coated particle contacted the cell membrane, the entire cell was labeled. The ganglion cells were classified into four types based on their soma size, dendritic-field size, branching pattern, and level of stratification. Broadly monostratified cells were classified into three types: RG(A) cells (large soma, large dendritic field); RG(B) cells (small- to medium-sized soma, small- to medium-sized dendritic field); and RG(C) cells (small- to medium-sized soma, medium-to-large dendritic field). Bistratified cells were classified as RG(D). Several subtypes were identified within each ganglion cell group. A number of new subtypes were discovered and added into the existing catalog, among them were two types of bistratified cells. This study therefore represents the most complete morphological classification of rat retinal ganglion cells available to date.

Animals↗