Lateral components in the cone terminals of the rabbit retina: horizontal cell origin and glutamate receptor expression.
We examined the identities of horizontal cell (HC) lateral components in cone terminals and the expression of glutamate receptors on the tips of HC dendrites. We injected A-type horizontal cells (AHCs) with neurobiotin and demonstrated that neurobiotin labeled completely all AHCs within a patch of retina. We converted neurobiotin by using diaminobenzidine and considered labeled processes to be from AHCs and unlabeled processes to be from B-type horizontal cells (BHCs). Three possible combinations of HC dendrites could exist in cone pedicles: both lateral components originating from AHCs, both from BHCs, or one from an AHC and the other from a BHC. EM observations revealed that a majority of cone terminals contained about equal numbers of lateral components originating from each of the two types of HCs and that each of the three possible combinations was present in equal numbers. Localization of different types of glutamate receptors on HC dendritic tips showed that 55% of AHC dendritic tips expressed AMPA receptors and 30% expressed kainate receptors, whereas, in the case of BHCs, 22% of dendritic tips expressed AMPA receptors and 33% expressed kainate receptors. This study suggests that cone photoreceptors feed the light signal equally into networks of AHCs and BHCs and that differential expression of AMPA/kainate receptors by different HCs could account for different functions.
Deng
Qiudong
Q
Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Republic of China.
Wang
Ling
L
Dong
Wei
W
He
Shigang
S
D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives; D003712:Dendrites / Q000378:metabolism; D005456:Fluorescent Dyes; D007150:Immunohistochemistry; D007546:Isoquinolines; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D017729:Presynaptic Terminals / Q000378:metabolism*; D011817:Rabbits; D018091:Receptors, AMPA / Q000096:biosynthesis; D017470:Receptors, Glutamate / Q000096:biosynthesis*; D018092:Kainic Acid Receptors / Q000096:biosynthesis; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D051248:Retinal Horizontal Cells / Q000166:cytology* / Q000648:ultrastructure
D001710:Biotin; D005456:Fluorescent Dyes; D007546:Isoquinolines; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D018092:Kainic Acid Receptors; C070614:neurobiotin; C017475:lucifer yellow