Responses of retinal axons in vivo and in vitro to position-encoding molecules in the embryonic superior colliculus.
We show that rat retinal ganglion cell axons exhibit no topographic specificity in growth along the rostral-caudal axis of the embryonic superior colliculus (SC). Position-related, morphological differences are not found between temporal and nasal axon growth cones. However, embryonic retinal axons respond in vitro to a position-dependent molecular property of SC membranes. In vivo, regional specificity in side branching is the earliest indication that axons make topographic distinctions along the rostral-caudal SC axis. Our contrasting in vivo and in vitro results indicate that molecules encoding rostral-caudal position in the SC neither guide nor restrict retinal axon growth, but may promote the development of topographic connections by controlling specificity in the extension or stabilization of branches.
Simon
D K
DK
Molecular Neurobiology Laboratory, Salk Institute, La Jolla, California 92037.
O'Leary
D D
DD
D000818:Animals; D001369:Axons / Q000502:physiology* / Q000648:ultrastructure; D002232:Carbocyanines; D002462:Cell Membrane / Q000502:physiology; D005456:Fluorescent Dyes; D005865:Gestational Age; D016501:Neurites / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000196:embryology* / Q000648:ultrastructure; D012165:Retinal Ganglion Cells / Q000502:physiology / Q000648:ultrastructure*; D013477:Superior Colliculi / Q000196:embryology* / Q000502:physiology
D002232:Carbocyanines; D005456:Fluorescent Dyes; C024286:3,3'-dioctadecylindocarbocyanine