A new look at calretinin-immunoreactive amacrine cell types in the monkey retina.
We have examined amacrine cells that are calretinin-immunoreactive (-IR) in the macaque monkey retina with the aim of classifying them into morphological and functional subtypes. There are calretinin-IR cells in the fovea and throughout the retina. Their highest density is reached at 1.0 mm from the foveal pit (10500 cells/mm(2)) and falls to 2600/mm(2) by 10 mm of eccentricity. Nearest-neighbor statistics for the calretinin-IR cell body distribution indicate a nonregular pattern, with a regularity index of 1.4-1.6. There is an increase or "bump" of cell density 3.5-4.0 mm from the foveal pit, corresponding to the rod photoreceptor density peak. Based on morphological differences, there appear to be three types of amacrine cell that are calretinin-IR. To determine the types, we doubly immunolabeled retinas, from fovea to periphery, for calretinin-IR in combination with other calcium binding proteins and inhibitory amino acid neurotransmitters. Labeling with parvalbumin and calretinin antibodies indicated that 70% of the amacrine cells were solely calretinin-IR, and 30% contained parvalbumin-IR as well. In the same way, 70% of the calretinin-IR amacrine cells colocalized calbindin, but 30% were only calretinin-IR. Among the calretinin/calbindin-colocalized cells, there were small-field and wide-field types. Double labeling with antibodies to calretinin and gamma-aminobutyric acid (GABA) and to calretinin and glycine revealed the majority to be glycine-IR, but some were GABA-IR. The glycine-IR population consists mainly of AII amacrine cell types, but clearly another non-AII type is involved. The non-AII glycine-IR population resembles a small- to medium-field diffuse type. The calretinin-IR wide-field type is GABAergic and corresponds to an A19 type. The central, rod-free, fovea contains the calretinin-IR, non-AII glycine-IR type and the calretinin-IR, GABAergic type only. To learn more concerning the circuitry of the calretinin/glycine-IR, non-AII amacrine cell type in isolation from AII amacrine cells, we concentrated on the rod-free fovea, where AII amacrine cells are absent. We performed a serial section electron microscopy (EM) study on four calretinin-IR cells. They were involved with cone pathway circuitry. They got input from ON and OFF midget bipolar cells, reciprocated synapses to these bipolar cells, and provided synapses to ON-center ganglion cells. Thus we have obtained new information on a cone pathway amacrine cell of the central monkey fovea that is involved in the midget system.
Kolb
Helga
H
John Moran Eye Center, University of Utah, Salt Lake City, Utah 84132, USA. helga.kolb@hsc.utah.edu
Zhang
Li
L
Dekorver
Laura
L
Cuenca
Nicolas
N
D025042:Amacrine Cells / Q000737:chemistry* / Q000648:ultrastructure*; D000818:Animals; D000906:Antibodies; D064032:Calbindin 2; D064026:Calbindins; D002452:Cell Count; D048429:Cell Size; D005584:Fovea Centralis / Q000166:cytology; D005998:Glycine / Q000032:analysis / Q000276:immunology; D008253:Macaca mulatta / Q000033:anatomy & histology*; D008854:Microscopy, Electron; D010320:Parvalbumins / Q000032:analysis / Q000276:immunology; D064030:S100 Calcium Binding Protein G / Q000032:analysis* / Q000276:immunology; D013569:Synapses / Q000737:chemistry / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000032:analysis / Q000276:immunology
D000906:Antibodies; D064032:Calbindin 2; D064026:Calbindins; D010320:Parvalbumins; D064030:S100 Calcium Binding Protein G; D005680:gamma-Aminobutyric Acid; D005998:Glycine