title: Distribution and size of ganglion cells in the retinae of large Amazon rodents.
abstract: The topographical distribution of density and soma size of the retinal ganglion cells were studied in three species of hystricomorph rodents. Flat-mounted retinae were stained by the Nissl method and the ganglion cells counted on a matrix covering the whole retinae. Soma size was determined for samples at different retinal regions. The agouti, a diurnal rodent, shows a well-developed visual streak, reaching a peak density of 6250 ganglion cells/mm2. The total number of ganglion cells ranged from 477,427-548,205 in eight retinae. The ganglion-cell-size histogram of the visual streak region exhibits a marked shift towards smaller values when compared to retinal periphery. Upper and lower regions differ in both cell density and cell size. The crepuscular capybara shows a less-developed visual streak with a peak ganglion cell density of 2250/mm2. The shift towards small-sized cells in the visual streak is less marked. Total ganglion cell population is 368,840. In the nocturnal paca, the upper half of the fundus oculi includes a tapetum lucidum. The retina of this species shows the least-developed visual streak of this group, with the lowest peak ganglion cell density reaching 925/mm2. The total ganglion cell number (230,804) is also smaller than in the two other species. Soma-size spectra of this species are characterized by the presence, in the lower hemi-retina, of very large perikarya comparable in size to the cat's alpha ganglion cells.
authors.affiliation: Department of Physiology, Federal University of Pará, Belém, Brazil.
authors.forename: L C
authors.initials: LC
authors.lastname: Silveira
authors.forename: C W
authors.initials: CW
authors.lastname: Picanço-Diniz
authors.forename: E
authors.initials: E
authors.lastname: Oswaldo-Cruz
mesh_terms: D000818:Animals; D002452:Cell Count; D005654:Fundus Oculi; D012160:Retina / Q000166:cytology* / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000166:cytology*; D012377:Rodentia / Q000033:anatomy & histology*; D009435:Synaptic Transmission; D014794:Visual Fields