title: Chromatic bipolar cell pathways in the mouse retina.
abstract: Like most mammals, mice feature dichromatic color vision based on short (S) and middle (M) wavelength-sensitive cone types. It is thought that mammals share a retinal circuit that in dichromats compares S- and M-cone output to generate blue/green opponent signals, with bipolar cells (BCs) providing separate chromatic channels. Although S-cone-selective ON-BCs (type 9 in mouse) have been anatomically identified, little is known about their counterparts, the M-cone-selective OFF-BCs. Here, we characterized cone connectivity and light responses of selected mouse BC types using immunohistochemistry and electrophysiology. Our anatomical data indicate that four (types 2, 3a/b, and 4) of the five mouse OFF-BCs indiscriminately contact both cone types, whereas type 1 BCs avoid S-cones. Light responses showed that the chromatic tuning of the BCs strongly depended on their position along the dorsoventral axis because of the coexpression gradient of M- and S-opsin found in mice. In dorsal retina, where coexpression is low, most type 2 cells were green biased, with a fraction of cells (≈ 14%) displaying strongly blue-biased responses, likely reflecting S-cone input. Type 1 cells were also green biased but did not comprise blue-biased "outliers," consistent with type 1 BCs avoiding S-cones. We therefore suggest that type 1 represents the green OFF pathway in mouse. In addition, we confirmed that type 9 BCs display blue-ON responses. In ventral retina, all BC types studied here displayed similar blue-biased responses, suggesting that color vision is hampered in ventral retina. In conclusion, our data support an antagonistically organized blue/green circuit as the common basis for mammalian dichromatic color vision.
authors.affiliation: Department of Biomedical Optics, Max Planck Institute for Medical Research, D-69120 Heidelberg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Breuninger
authors.forename: Christian
authors.initials: C
authors.lastname: Puller
authors.forename: Silke
authors.initials: S
authors.lastname: Haverkamp
authors.forename: Thomas
authors.initials: T
authors.lastname: Euler
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics; D003116:Color; D003118:Color Perception / Q000502:physiology; D055253:Color Vision / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D008027:Light; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D015233:Models, Statistical; D055355:Opsins / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D019887:Peanut Agglutinin / Q000378:metabolism; D010636:Phenols / Q000378:metabolism; D010775:Photic Stimulation / Q000379:methods; D011971:Receptors, Immunologic / Q000235:genetics; D018042:Receptors, Neurokinin-3 / Q000235:genetics; D012160:Retina / Q000166:cytology*; D051245:Retinal Bipolar Cells / Q000145:classification / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000145:classification / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*
chemical_list: C482560:CLM-1 protein, mouse; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; C558698:MItoP compound; D055355:Opsins; D009943:Organophosphorus Compounds; D019887:Peanut Agglutinin; D010636:Phenols; D011971:Receptors, Immunologic; D018042:Receptors, Neurokinin-3; C102474:cytohesin-2; D049452:Green Fluorescent Proteins