Abstract
Purpose: :
To identify and morphologically classify amacrine cell types in the zebrafish retina.
Methods: :
The morphological types of amacrine cells in the zebrafish retina were identified using retinal slices and DiOlistic techniques. Using a gene gun, retinal slices were shot with microcarriers coated with DiI dye. Amacrine cell types were classified according to dendritic field diameter, stratification, and branching/arborization patterns.
Results: :
Amacrine somata were found at the INL/IPL border. Dendritic processes of each cell type ramified in distinct sublayers of the IPL. Overall, 27 amacrine cell types, identified as presumed OFF- (n = 9), ON- (n = 6), and ON/OFF- (n = 6) cells, were initially classified based on dendritic stratification patterns. Diffuse amacrine cells and cells with processes restricted to the mid-IPL were also identified, though less often. Processes of OFF-type cells ramified throughout sublamina a and were characterized by scattered varicosities. These cells were either monostratified, with processes restricted to the s1, s2, or s3 sublayers, or were bistratified s1/s2 or s1/s3. Within these groups, further subtypes were identified based on dendritic field size, the presence or absence of an apical dendrite, and symmetry of the dendritic field. ON-type cells were characterized by an apical dendrite projecting directly to s5 or s6 of sublamina b before extending lateral processes within that sublayer. Dendritic arbors of these cells were dotted with varicosities and ranged in size from narrow to wide-field. Bistratified ON/OFF-cells had dendritic processes identified in either s1/s4, s1/s5, s1/s6, or s2/s5. Three of these cell types had an apical dendrite and medium- to wide-field dendritic diameters. Diffuse amacrine cells had dendritic processes throughout s1-s6 of the IPL and dendritic field diameters ranged in size from narrow- to medium-field.
Keywords: amacrine cells • retina: proximal (bipolar, amacrine, and ganglion cells) • anatomy