Dendritic morphologies of retinal ganglion cells projecting to the lateral geniculate nucleus in the rabbit

Small injections of fluorescent Rhodamine-latex microspheres and Fast Blue were made into the dorsal lateral geniculate nucleus (dLGN) of fifteen rabbits. After 8-15 day survival times, the somas of projecting ganglion cells were found to be labelled in the contralateral retinas by retrograde transport. The dendritic morphologies of the labelled ganglion cells were revealed by intracellular injection of Lucifer Yellow or horseradish peroxidase while superfusing the retinas. At least ten distinct dendritic morphologies were observed among 161 injected ganglion cells. The three most commonly recovered dendritic morphologies were those of: (1) alpha-like cells; (2) large, complex dendritic field cells; and (3) cells with small, dense dendritic fields that resemble intracellularly identified brisk sustained cells (Amthor et al., J. Comp. Neurol. 1989; 280:72-96). Smaller percentages of cells whose dendritic morphologies resembled those of several physiologically identified sluggish and complex receptive field ganglion cell classes (Amthor et al., J. Comp. Neurol. 1989; 280:72-96, 97-21) were also recovered. Several morphological types were also found that were previously unknown or could not be confidently related to those of previously known classes. Most dLGN injections labelled many different types of ganglion cells, but restricted injections in some dLGN loci labelled only a limited number of ganglion cell classes.