Dendritic growth and remodeling of cat retinal ganglion cells during fetal and postnatal development

Abstract

We have studied the development of retinal ganglion cell morphology in the cat's visual system from early fetal to postnatal times. In particular, we have examined the contribution of growth and remodeling to the establishment of mature retinal ganglion cell form. Ganglion cells were identified by retrograde labeling with rhodamine latex microspheres deposited in the superior colliculus and lateral geniculate nucleus between embryonic day 34 (E34; birth = E65) and adulthood. To reveal the fine morphological details of retrogradely labeled ganglion cells, 48 hr later Lucifer yellow was injected intracellularly in living retinae that had been dissected and maintained in vitro. Our results show that at E35-37 the majority of ganglion cells are very simple in morphology, with a few dendritic processes that are generally aligned in a radial direction towards or away from the optic disc. During the ensuing 2 week period, there is a progressive growth and elaboration of dendrites. By E50, some ganglion cells resembling the adult alpha, beta, and gamma classes can be identified based on comparisons of the appearance and dimensions of their dendritic trees and somata with neighboring filled cells. However, ganglion cell dendrites and axons at this age express several transient morphological features. The axons of ganglion cells give rise to delicate processes originating from the intraretinal portion of the axon, including side branches, present in about half of the cells, and occasionally bifurcations that give rise to axon collaterals. These transient axonal features are present throughout development, including the neonatal period; no axon collaterals were observed after postnatal day 15, while axonal side branches persisted even at P31 but were gone by adulthood. Ganglion cell dendrites exhibit excessive branches and exuberant somatic and dendritic spines. Quantitative analysis of these processes shows that after E45 dendritic trees increase dramatically in complexity, reaching the peak number of spines and branch points by the first week of postnatal life. The number of dendritic processes then falls abruptly to reach near-adult levels by the end of the first postnatal month. Even though dendritic morphology closely resembles that seen in the adult at this age, ganglion cell bodies and dendrites must continue to grow to reach their adult size.(ABSTRACT TRUNCATED AT 400 WORDS)

Development and regulation of dendritic stratification in retinal ganglion cells by glutamate-mediated afferent activity

“…First, we describe the time course of beta cell dendritic stratification in the central and * Distinct classes of RGCs could be recognized in retinal wholemounts by ESO, some 2 weeks before birth. This is in accord with the results of Ramoa et al (1988) who examined the morphological development of fetal cat RGCs labeled by intracellular injection of Lucifer yellow. As may be seen in Figure 1, beta cells could be readily distinguished from other RGC classes by their relatively short, bushy dendrites branching in close proximity to the cell body.…”

“…RGCs with dendrites that stratify in the inner portion of the IPL signal information about increments of light, while those with dendrites stratifying in the outer portion of the IPL signal light decrements (Famiglietti and Kolb, 1976;Nelson et al, 1978). Whereas in the mature cat retina the dendrites of ON and OFF alpha and beta RGCs are unistratified, early in development the dendritic processes of these neurons have been noted to ramify throughout the IPL (Maslim and Stone, 1988;Dann et al, 1988;Ramoa et al, 1988). Although, the precise time course of the stratification process has yet to be determined, it has been reported in the developing cat retina that this occurs around the time that bipolar cells form synapses in the IPL (Mashm andStone, 1986, 1988).…”

Preferential Termination of Corticorubral Axons on Spine-Like Dendritic Protrusions in Developing Cat

“…SLDPs emanate from the dendritic shaft and show pleomorphic morphological features, including filiform structures distinct from the dendritic spines in adults (e.g., Morest, 1969;Scheibel et al, 1973). They also transiently increase in number at an early stage of development (e.g., Morest, 1969;Scheibel et al, 1973;Lund et al, 1977;Boothe et al, 1979;Garey and Saini, 1981;Hammer et al, 1981;Phelps et al, 1983;Dvergsten et al, 1986;Ramoa et al, 1988). These in vivo findings suggest that SLDPs are continuously remodeled in development.…”

Localization and developmental expression of the NMDA receptor subunit NR2A in the mammalian retina

“…In the retina, ganglion cells go through a transient phase with profuse branching and an excessive number of spine-like dendritic processes (cat: Dann et al, 1988;Ramoa et al, 1988;rat: Yamasaki and Ramoa, 1993;hamster: Lau et al, 1992b). It has been suggested that these spine-like processes are the initial targets for synaptic input from bipolar and amacrine cells, but this has not been confirmed at the ultrastructural level (Wong et al, 1992).…”