DIFFERENCE IN PNA LABEL INTENSITY BETWEEN SHORT-WAVELENGTH AND MIDDLE-WAVELENGTH SENSITIVE CONES IN THE GROUND-SQUIRREL RETINA

Purpose. Peanut agglutinin lectin (PNA) is known for its selective bin ding to cone cells and to the cone domains of the interphotoreceptor m atrix. In the current study, the authors investigated whether there is any difference in PNA binding between color-specific cones of the con e-dominant ground squirrel. Methods. Consecutive serial sections of th e retina of Spermophilus tridecemlineatus were reacted alternately wit h PNA and antivisual pigment antibodies. The PNA labels associated wit h short-middle-wavelength-sensitive cones (S-cones and M-cones, respec tively) were compared with fluorescent lectin cytochemistry.Results. A lthough all rod-like cells were left unstained, the cones exhibited a specific lectin label. There was, however, a significant difference be tween the two cone types; the intensity of the ring-like PNA label in the matrix sheath around S-cones significantly exceeded that of the M- cones. Conclusions. The difference in PNA label intensity indicates a difference in the composition of the matrix sheaths surrounding the tw o respective cone types. To the authors' knowledge, this is the first report on lectin-cytochemical discrimination of cone matrix sheaths an d the first lectin study in the ground squirrel retina leading to the observation that PNA can distinguish the three characteristic photorec eptor types in this animal. In this respect, the rod-like cells of the ground squirrel retina were shown to be no different from rod cells o f other species.