Time of origin of cortico-collicular projection neurons in the rat visual cortex.
The time of origin and the radial gradient of neurogenesis of cortico-collicular neurons have been studied in the rat visual area 17. We used a combined technique for the histochemical detection of the retrogradely transported horseradish peroxidase from the superior colliculus and the autoradiographic detection of the [3H]-thymidine administered during the gestational period. The cortico-collicular neurons of visual area 17 are located in layer V and are generated on gestational day (GD) 15 (59.78%), GD 16 (36.21%), and GD 17 (4.01%). This finding reveals that, for the cortico-collicular neuronal population, the birth date is well-correlated with the laminar position in the adult animal. To see whether the cortico-collicular neurons located at various radial levels of layer V are generated concurrently, or whether they follow an "inside-out" pattern of positioning, we divided layer V into three (upper, middle and lower) sublaminae. Most cortico-collicular neurons located in the lower two-thirds of layer V are generated on GD 15 (65%), whereas the neurons located in the upper third of the layer are generated both on GD 15 and GD 16 in almost equal proportions (52.53% and 44.39%, respectively).
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Departamento de Ciencias Morfológicas, Facultad de Medicina, Universidad de Zaragoza, Spain.
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D000818:Animals; D005260:Female; D006651:Histocytochemistry; D006735:Horseradish Peroxidase; D009474:Neurons / Q000502:physiology*; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D013477:Superior Colliculi / Q000502:physiology*; D013936:Thymidine; D014793:Visual Cortex / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D014795:Visual Pathways / Q000166:cytology / Q000254:growth & development / Q000502:physiology
D006735:Horseradish Peroxidase; D013936:Thymidine