Displaced retinal ganglion cells (DRGCs) were retrogradely labelled by
injections of the
fluorescent dye Fast Blue into the superior colliculi of pigmented rats. Following fixation these cells were intracellularly injected with
Lucifer Yellow to determine their dendritic morphology and distribution. Graphic reconstruction of
Lucifer Yellow-filled prelabelled neurones revealed a heterogeneous population of DRGCs. Their stratification within the inner plexiform layer was diverse and cells were classified according to their dendritic morphology. The present sample consists largely of unistratifying neurones, the dendrites of which arborized within a narrow sublamina of the inner plexiform layer. They were characterized by a centrally located
soma and densely branched dendritic network with little overlap within the branching pattern. In contrast, bistratifying DRGCs possessed a loose and sparsely branched dendritic structure, while diffusely stratifying neurones contained a high degree of dendritic crossing, culminating in a complex network, in which the
soma position was biased toward the periphery. One type of DRGC bore a striking resemblance to type 1 neurones (Perry, 1979; Proc. R. Soc. Lond. [Biol.] 204:363-375) in the
ganglion cell layer. They were characterized by a large
soma (15.5 micron +/- 2.2 micron s.d.) and a dendritic field diameter averaging 288 micron (s.d. +/- 62 micron) and were on average larger than the rest of the displaced population but smaller than type 1 cells in the
ganglion cell layer. Since the stratification patterns of the displaced and nondisplaced type 1 neurones were indistinguishable, it is reasonable to assume that the
Lucifer Yellow-filled cells in the present study represent the displaced counterpart of regular type 1
ganglion cells.(ABSTRACT TRUNCATED AT 250 WORDS)