Abstract
Abstract: :
Purpose: To examine the morphological maturation of amacrine cells expressing NK1 receptor, focusing on the period from postnatal day 5 (P5) when the outer plexiform layer is formed, to postnatal day 13 (P13) when the eyes open. Methods: The retinae of Sprague–Dawley rats at postnatal day (P) 5, 7, 10 and 13 were immunolabeled with an antibody against NK1 receptor (Chemicon, 1:5,000). Double labeling using antibodies against NK1 receptor and recoverin or GABA or glycine or glutamine synthase (GS) were applied, and apoptotic cell death was determined by TUNEL assay. Results: In the adult retina, numerous NK1 receptor–IR amacrine cells were located in the inner nuclear layer (INL) adjacent to the inner plexiform layer (IPL), and their processes emerging from the somata branched and stratified at 1, 2, and 5 strata of within the IPL. NK1 receptor–IR amacrine cells were observed at P5. The cell bodies were located in the middle of inner INL and their processes branched and formed two distinct bands in the IPL. At P10 NK1 receptor–IR amacrine cells formed three distinct bands and at p13 three bands occupied the same strata as those of the adult. In addition, some labeled cells had horizontal processes which formed plexiform–like structures within the INL. The period of presence of this type of cells matches with that of apoptosis of bipolar and amacrine cells in the INL during development. This cell type with horizontal processes was frequently observed at P7, rarely at P10, and not at P13 and in the adult. Conclusions: NK1 receptor–IR amacrine cells morphologically and functionally complete the maturation process around the time of P13 and NK1 receptor–IR unclassified cells might play an important role in the positioning of bipolar and amacrine cells in the developing rat retina.
Keywords: retina • retina: proximal (bipolar, amacrine, and ganglion cells) • retinal development