S-cones do not contribute to the OFF-midget pathway in the retina of the marmoset, Callithrix jacchus

Eur J Neurosci. 2005 Jul;22(2):437-47. doi: 10.1111/j.1460-9568.2005.04231.x.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons
  • Callithrix / physiology*
  • Cell Count / methods
  • Excitatory Amino Acid Transporter 2 / metabolism
  • Female
  • Immunohistochemistry / methods
  • Lewis X Antigen / metabolism
  • Male
  • Peanut Agglutinin / metabolism
  • Retina / cytology*
  • Retina / metabolism*
  • Retinal Cone Photoreceptor Cells / physiology*
  • Rod Opsins / metabolism
  • Visual Pathways / physiology*

Substances

  • Excitatory Amino Acid Transporter 2
  • Lewis X Antigen
  • Peanut Agglutinin
  • Rod Opsins