Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina
IntroductionLight responses of rod photoreceptor cells traverse the retina through three pathways. The primary pathway involves synapses from rods to ON-type rod bipolar cells with OFF signals reaching retinal ganglion cells (RGCs) via sign-inverting glycinergic synapses. Secondly, rod signals can e...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2023-03-01
|
| Series: | Frontiers in Ophthalmology |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/fopht.2023.1146785/full |
| _version_ | 1811159561178972160 |
|---|---|
| author | Asia L. Sladek Wallace B. Thoreson Wallace B. Thoreson |
| author_facet | Asia L. Sladek Wallace B. Thoreson Wallace B. Thoreson |
| author_sort | Asia L. Sladek |
| collection | DOAJ |
| description | IntroductionLight responses of rod photoreceptor cells traverse the retina through three pathways. The primary pathway involves synapses from rods to ON-type rod bipolar cells with OFF signals reaching retinal ganglion cells (RGCs) via sign-inverting glycinergic synapses. Secondly, rod signals can enter cones through gap junctions. Finally, rods can synapse directly onto cone OFF bipolar cells.MethodsTo analyze these pathways, we obtained whole cell recordings from OFF-type α RGCs in mouse retinas while expressing channelrhodopsin-2 in rods and/or cones.ResultsOptogenetic stimulation of rods or cones evoked large fast currents in OFF RGCs. Blocking the primary rod pathway with L-AP4 and/or strychnine reduced rod-driven optogenetic currents in OFF RGCs by ~1/3. Blocking kainate receptors of OFF cone bipolar cells suppressed both rod- and cone-driven optogenetic currents in OFF RGCs. Inhibiting gap junctions between rods and cones with mecloflenamic acid or quinpirole reduced rod-driven responses in OFF RGCs. Eliminating the exocytotic Ca2+ sensor, synaptotagmin 1 (Syt1), from cones abolished cone-driven optogenetic responses in RGCs. Rod-driven currents were not significantly reduced after isolating the secondary pathway by eliminating Syt1 and synaptotagmin 7 (Syt7) to block synaptic release from rods. Eliminating Syt1 from both rods and cones abolished responses to optogenetic stimulation. In Cx36 KO retinas lacking rod-cone gap junctions, optogenetic activation of rods evoked small and slow responses in most OFF RGCs suggesting rod signals reached them through an indirect pathway. Two OFF cells showed faster responses consistent with more direct input from cone OFF bipolar cells.DiscussionThese data show that the secondary rod pathway supports robust inputs into OFF α RGCs and suggests the tertiary pathway recruits both direct and indirect inputs. |
| first_indexed | 2024-04-10T05:43:16Z |
| format | Article |
| id | doaj.art-89cdfa0b54a4487ebe7ccdc29cd186de |
| institution | Directory Open Access Journal |
| issn | 2674-0826 |
| language | English |
| last_indexed | 2024-04-10T05:43:16Z |
| publishDate | 2023-03-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Ophthalmology |
| spelling | doaj.art-89cdfa0b54a4487ebe7ccdc29cd186de2023-03-06T05:32:14ZengFrontiers Media S.A.Frontiers in Ophthalmology2674-08262023-03-01310.3389/fopht.2023.11467851146785Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retinaAsia L. Sladek0Wallace B. Thoreson1Wallace B. Thoreson2Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE, United StatesTruhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE, United StatesPharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, United StatesIntroductionLight responses of rod photoreceptor cells traverse the retina through three pathways. The primary pathway involves synapses from rods to ON-type rod bipolar cells with OFF signals reaching retinal ganglion cells (RGCs) via sign-inverting glycinergic synapses. Secondly, rod signals can enter cones through gap junctions. Finally, rods can synapse directly onto cone OFF bipolar cells.MethodsTo analyze these pathways, we obtained whole cell recordings from OFF-type α RGCs in mouse retinas while expressing channelrhodopsin-2 in rods and/or cones.ResultsOptogenetic stimulation of rods or cones evoked large fast currents in OFF RGCs. Blocking the primary rod pathway with L-AP4 and/or strychnine reduced rod-driven optogenetic currents in OFF RGCs by ~1/3. Blocking kainate receptors of OFF cone bipolar cells suppressed both rod- and cone-driven optogenetic currents in OFF RGCs. Inhibiting gap junctions between rods and cones with mecloflenamic acid or quinpirole reduced rod-driven responses in OFF RGCs. Eliminating the exocytotic Ca2+ sensor, synaptotagmin 1 (Syt1), from cones abolished cone-driven optogenetic responses in RGCs. Rod-driven currents were not significantly reduced after isolating the secondary pathway by eliminating Syt1 and synaptotagmin 7 (Syt7) to block synaptic release from rods. Eliminating Syt1 from both rods and cones abolished responses to optogenetic stimulation. In Cx36 KO retinas lacking rod-cone gap junctions, optogenetic activation of rods evoked small and slow responses in most OFF RGCs suggesting rod signals reached them through an indirect pathway. Two OFF cells showed faster responses consistent with more direct input from cone OFF bipolar cells.DiscussionThese data show that the secondary rod pathway supports robust inputs into OFF α RGCs and suggests the tertiary pathway recruits both direct and indirect inputs.https://www.frontiersin.org/articles/10.3389/fopht.2023.1146785/fullrodsconesoptogeneticsretinasynaptotagminrod pathways |
| spellingShingle | Asia L. Sladek Wallace B. Thoreson Wallace B. Thoreson Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina Frontiers in Ophthalmology rods cones optogenetics retina synaptotagmin rod pathways |
| title | Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina |
| title_full | Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina |
| title_fullStr | Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina |
| title_full_unstemmed | Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina |
| title_short | Using optogenetics to dissect rod inputs to OFF ganglion cells in the mouse retina |
| title_sort | using optogenetics to dissect rod inputs to off ganglion cells in the mouse retina |
| topic | rods cones optogenetics retina synaptotagmin rod pathways |
| url | https://www.frontiersin.org/articles/10.3389/fopht.2023.1146785/full |
| work_keys_str_mv | AT asialsladek usingoptogeneticstodissectrodinputstooffganglioncellsinthemouseretina AT wallacebthoreson usingoptogeneticstodissectrodinputstooffganglioncellsinthemouseretina AT wallacebthoreson usingoptogeneticstodissectrodinputstooffganglioncellsinthemouseretina |