Related Experiment Video
Updated: May 28, 2026
Investigating Retinal Circuits and Molecular Localization by Pre-Embedding Immunoelectron Microscopy
Published on: July 12, 2024
Immunohistochemical identification and synaptic inputs to the diffuse bipolar cell type DB1 in macaque retina
Theresa Puthussery1, Jacqueline Gayet-Primo, W Rowland Taylor
1Casey Eye Institute, Department of Ophthalmology, Oregon Health and Sciences University, Portland, Oregon 97239, USA. puthusse@ohsu.edu
Insights
Researchers identified secretagogin as a marker to study primate DB1 bipolar cells. This revealed DB1 bipolar cells primarily connect with cone photoreceptors, with some rod pathway input suggested by glycine receptor expression.
Area of Science:
- Neuroscience
- Ophthalmology
- Cell Biology
Background:
- Detailed analysis of primate DB1 bipolar cells was limited by the lack of specific immunohistochemical markers.
- Understanding synaptic inputs to bipolar cells is crucial for comprehending visual processing in the primate retina.
Purpose of the Study:
- To identify a reliable immunohistochemical marker for primate DB1 bipolar cells.
- To characterize the synaptic connections of DB1 bipolar cells with photoreceptors and other retinal neurons.
Main Methods:
- Utilized antibodies against the EF-hand calcium-binding protein, secretagogin, for immunohistochemical labeling.
- Employed electron microscopy to examine synaptic contacts at the cone pedicle.
- Performed double labeling with glutamate and glycine receptor subunit antibodies.
Main Results:
- Secretagogin strongly labels DB1 bipolar cells and GABAergic amacrine cells in the macaque retina.
- DB1 bipolar cells form synaptic contacts with L/M and S-cone photoreceptors, with minimal rod photoreceptor input.
- Electron microscopy revealed flat contacts at triad-associated and non-triad-associated positions on cone pedicles.
- Glycine receptor GlyRα1 expression was observed at DB1 bipolar cell contacts with AII amacrine cells.
Conclusions:
- Secretagogin is a valuable marker for studying DB1 bipolar cells and associated amacrine cells in primate retinas.
- DB1 bipolar cells are primarily cone-driven, receiving input from both L/M and S-cones.
- The presence of GlyRα1 suggests potential input from the rod pathway to DB1 bipolar cells via AII amacrine cells.
Abstract:
Detailed analysis of the synaptic inputs to the primate DB1 bipolar cell has been precluded by the absence of a suitable immunohistochemical marker. Here we demonstrate that antibodies for the EF-hand calcium-binding protein, secretagogin, strongly label the DB1 bipolar cell as well as a mixed population of GABAergic amacrine cells in the macaque retina. Using secretagogin as a marker, we show that the DB1 bipolar makes synaptic contact with both L/M as well as S-cone photoreceptors and only minimal contact with rod photoreceptors. Electron microscopy showed that the DB1 bipolar makes flat contacts at both triad-associated and nontriad-associated positions on the cone pedicle. Double labeling with various glutamate receptor subunit antibodies failed to conclusively determine the subunit composition of the glutamate receptors on DB1 bipolar cells. In the IPL, DB1 bipolar cell axon terminals expressed the glycine receptor, GlyRα1, at sites of contact with AII amacrine cells, suggesting that these cells receive input from the rod pathway.
