Cellular morphology in the visual layer of the developing rat superior colliculus

Abstract

Golgi studies were undertaken in the superficial (visual) superior colliculus of 53 rat pups (106 colliculi) from birth to 31 days postnatal. Golgi-Cox techniques revealed discrete periods of development based upon changes in cell morphology. Major orientation of cells occurred between birth and 3 days postnatal. From 4 to 5 days postnatal, major cell populations could be identified, as (1) marginal cells; (2) horizontal cells; (3) piriform cells; (4) narrow-field vertical cells; (5) wide-field vertical cells; and (6) stellate cells. The period from 6 to 8 days was marked by a significant increase in dendritic growth cones, spicules, and varicosities, accompanied by some dendritic elongation and branching. From 9 to 10 days postnatal, further increases in dendritic elongation and branching occurred, with disappearance of dendritic growth cones, spicules, and varicosities. Further dendritic growth and branching was observed between 15 and 23 days. The period between 23 and 31 days was characterized by the appearance of spiny types of all cell populations. Correlations between these periods of cellular differentiation and stages of synaptogensis are discussed.