Abstract
Abstract: :
Purpose: To quantitatively analyze the dendritic stratification of retinal ganglion cells (RGC) during postnatal development. Methods: The dendritic stratification patterns of RGCs were quantitatively determined from P12– and P33–aged YFP–expressing mice reared under cyclic light/dark conditions or constant darkness from birth. The dendritic stratification of each RGC was characterized by the ramification depth and width in the IPL, which was defined as 0–100 % from the border of inner nuclear layer to the border of ganglion cell layer. Results: (1) In a total of 162 RGCs of P33–aged mice reared under cyclic light/dark conditions, 42% RGCs have dendrites ramified exclusively in the sublamina b with their peak dendritic density located between 60–80% of the IPL, and 26% of the RGCs ramified exclusively in sublamina a with their peak dendritic density located between 20–40% of the IPL. Twenty–two percent of RGCs have dendrites clearly separated into 2 layers and bistratified in both sublamina a and b. Another 10% RGCs ramified their dendrites close to the center of the IPL and extended into both sublaminae. (2) Almost all morphologically identified RGCs were found in P12–aged mice reared under cyclic light/dark conditions. The dendritic stratification patterns of the RGCs at this age, however, were significantly different from that of the mice at the age of P33. Nearly 80% of RGCs ramified their dendrites between 50–70% of the IPL. The percentages of bistratified RGCs and the RGCs with dendrites ramified exclusively in the sublamina b of IPL were 9% and 11%, respectively, which were much lower than that of the mice at the age of P33. (3) A total of 199 RGCs were studied in P33–aged mice reared under constant darkness. Forty–five percent of RGCs ramified their dendrites in the sublamina b with their peak dendritic density located between 60–80% of the IPL, which was not significantly different from that of the age matched controls. However, the percentages of bistratified RGCs (12%) and the RGCs with dendrites ramified exclusively in sublamina a of the IPL (13%) were much lower, and the percentage of RGCs (29%) with dendrites ramified close to the center of the IPL was much higher than that of age matched controls. Conclusions: RGC dendritic stratification was continuously refined after eye opening. Light deprivation retarded the maturation of RGCs with bistratified dendrites and RGCs with dendrites exclusively ramified in the sublamina b of the IPL.
Keywords: retinal connections, networks, circuitry • retina: proximal (bipolar, amacrine, and ganglion cells)