The development of retinal ganglion cell dendritic stratification in ferrets

A-signature feature of mature ferret retinal ganglion cells (RGCs) is the s tratification of their dendrites within either ON or OFF sublayers of the r etinal inner plexiform layer (IPL). Dendritic stratification is achieved th rough the gradual restriction of RGC dendrites which initially ramify throu ghout the IPL. We examined the time course of stratification by retrogradel y labeling ferret retinas with DiI at various postnatal ages; Stratificatio n of beta and alpha RGC dendrites into either the ON or OFF sublayers of th e IPL begins around postnatal day 5, when class-specific morphologies begin to emerge, and is largely completed by eye opening, at the end of the firs t postnatal month. Our results imply that dendritic stratification of ferre t ON and OFF RGCs, as in other mammals, occurs independently of visually dr iven activity. port (C) 1999 Lippincott Williams & Wilkins.