Organization of callosal connections in the visual cortex of the rabbit following neonatal enucleation, dark rearing, and strobe rearing.
The organization of visual callosal projections was studied in (1) normal adult rabbits; (2) adult rabbits which had undergone monocular enucleation (ME) or binocular enucleation (BE) at birth; and (3) adult rabbits which had been deprived of normal visual experience during development by dark rearing (DR) or strobe rearing (SR). Previously published observations (Murphy and Grigonis, Behav Brain Res 30:151, 1988) on callosal organization in adult rabbits in which retinal ganglion cell activity was eliminated during development by intraocular tetrodotoxin (TTX) injections, are also summarized for comparison with these data. The tangential extent of the callosal cell zone was significantly larger than normal in DR, TTX, and ME rabbits, was unchanged in BE rabbits, and was significantly reduced in SR rabbits. An analysis of the laminar distribution of the callosal cells revealed a significant increase in the percentage of callosal cells in lamina IV in ME, DR, and TTX animals. Measurements of density of callosal cells showed a significant increase in the density of the callosal projection in ME and SR rabbits and a decrease in density in BE rabbits compared with normal. The data suggest that the mechanisms involved in the development of the tangential and laminar organization of the callosal cell zone are different. In addition, the data suggest that the mechanisms involved in the maintenance of callosal projections are different from the mechanisms involved in the elimination of callosal projections during development. The effects of these developmental manipulations on callosal organization in other mammals are reviewed and compared with the effects in rabbits. The data suggest that species differences in the degree of maturity of the visual system at birth and in the extent of callosal development at the time of eye opening, may underlie species differences in the effects of these manipulations on the organization of visual callosal projections during development.
Grigonis
A M
AM
Department of Anatomy, Hahnemann University, Philadelphia, Pennsylvania 19102-1192.
Murphy
E H
EH
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D003337:Corpus Callosum / Q000166:cytology* / Q000254:growth & development; D003624:Darkness; D015353:Eye Enucleation; D006651:Histocytochemistry; D006735:Horseradish Peroxidase; D009434:Neural Pathways / Q000166:cytology / Q000254:growth & development; D010775:Photic Stimulation; D011817:Rabbits; D013779:Tetrodotoxin / Q000008:administration & dosage / Q000494:pharmacology; D015349:Vision, Monocular / Q000502:physiology; D014793:Visual Cortex / Q000166:cytology* / Q000254:growth & development
D013779:Tetrodotoxin; D006735:Horseradish Peroxidase