Color-opponent responses of small and giant bipolar cells in the carp retina

• Published in: Visual neuroscience 2000-07, Vol.17 (4), p.609-621
• Main Authors: SHIMBO, KIYOSHI, TOYODA, JUN-ICHI, KONDO, HIROAKI, KUJIRAOKA, TORU
• Format: Article
• Language: English
• Subjects: Amacrine cells; Animals; Biological and medical sciences; Carps - physiology; Cell Membrane - physiology; Color Perception - physiology; Electron microscopy; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; Horizontal cells; Horseradish Peroxidase; Interneurons - cytology; Interneurons - physiology; Membrane conductance; Membrane Potentials; Photoreceptors; Retina - cytology; Retina - physiology; Vertebrates: nervous system and sense organs
• ISSN: 0952-5238; 1469-8714
• DOI: 10.1017/S0952523800174103

The physiological and morphological properties of color-opponent bipolar cells in the carp retina were studied. Fifty nine OFF-center bipolar cells and 63 ON-center bipolar cells out of about 500 total bipolar cells recorded showed color-opponent responses. The OFF-center color-opponent bipolar cells were classified into three subgroups according to their spectral and spatial responses. Fifty OFF-center color-opponent cells responded with depolarization to a blue light spot and with hyperpolarization to a red spot in the receptive-field center. The polarity of the surround response was opposite to that of center response at each wavelength. Therefore these cells were classified as OFF double-opponent cells (OFF-DO). Eight cells responded with hyperpolarization to a blue and green spot and with depolarization to a red spot. The surround responses of those cells were depolarizing at any wavelength (R+G− cell). One responded with hyperpolarization to a blue and red spot and with depolarization to a green spot. The surround response showed a different spectral characteristic from that of the center response. It responded with depolarization to a blue and green annulus and with hyperpolarization to a red annulus (R−G+B− cell). The ON-center color-opponent bipolar cells were similarly classified into three subgroups. Sixty of ON-center color-opponent cells were the double color-opponent type (ON-DO cell), showing the responses of opposite polarity to the OFF-DO cells. Two cells were classified as R−G+ cell, and one cell as R+G−B+ cell. Both OFF- and ON-DO cells were identified by their morphology as Cajal's giant bipolar cells, and R+G−, R−G+, R−G+B−, and R+G−B+ cells as Cajal's small bipolar cells. The analysis of the latency and the ionic mechanisms of their responses suggest that DO cells under light-adapted conditions receive direct inputs from long-wavelength (red) cones, RG cells from middle-wavelength (green) cones, and RGB cells from short-wavelength (blue) cones. Possible mechanisms of the opponent inputs to these bipolar cells are discussed.