title: S-cones do not contribute to the OFF-midget pathway in the retina of the marmoset, Callithrix jacchus.
abstract: It is well established that in primate retina both medium- and long-wavelength-sensitive cone types provide input to the midget-parvocellular pathway. The question, however, whether short-wavelength-sensitive (S or 'blue') cones provide input to the OFF-division of the midget-parvocellular pathway is still controversial. In the present study, we investigated the connections of nearly 400 S-cones with OFF-midget bipolar cells in central and peripheral retina of a New World monkey, the marmoset. Horizontal sections or pieces of whole retinae were double-labelled with an antiserum to S-cone opsin to identify S-cones and antibodies to the cell adhesion molecule CD15 to identify OFF-midget bipolar cells. Peanut agglutinin coupled to a fluorescent tag was used to label the cone pedicles of all cone types. Peanut agglutinin was also used to distinguish S-cones from the other cone types. The sections were analysed with deconvolution microscopy. We found that nearly all pedicles of medium- and long-wavelength-sensitive cones are located opposite distinct dendritic clusters formed by OFF-midget bipolar cells. By contrast, the S-cone pedicles are not located opposite dendritic clusters. Instead, S-cones make sparse contacts with CD15-labelled processes. Some of these processes protruded from OFF-midget bipolar clusters, whereas others could be traced to a diffuse bipolar cell type. Thus, in the marmoset retina the midget-parvocellular system does not carry a blue-OFF signal.
authors.affiliation: The National Vision Research Institute of Australia, The University of Melbourne, Carlton VIC 3053, Australia.
authors.forename: Sammy C S
authors.initials: SC
authors.lastname: Lee
authors.forename: Ildiko
authors.initials: I
authors.lastname: Telkes
authors.forename: Ulrike
authors.initials: U
authors.lastname: Grünert
mesh_terms: D000818:Animals; D001369:Axons; D002144:Callithrix / Q000502:physiology*; D002452:Cell Count / Q000379:methods; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D005260:Female; D007150:Immunohistochemistry / Q000379:methods; D016256:Lewis X Antigen / Q000378:metabolism; D008297:Male; D019887:Peanut Agglutinin / Q000378:metabolism; D012160:Retina / Q000166:cytology* / Q000378:metabolism*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D017299:Rod Opsins / Q000378:metabolism; D014795:Visual Pathways / Q000502:physiology*
chemical_list: D027342:Excitatory Amino Acid Transporter 2; D016256:Lewis X Antigen; D019887:Peanut Agglutinin; D017299:Rod Opsins