NEURITE OUTGROWTH THROUGH LESIONS OF NEONATAL OPOSSUM SPINAL-CORD IN CULTURE

The aim of these experiments was to analyze neurite outgrowth during r egeneration of opossum spinal cord isolated from Monodelphis domestica and maintained in culture for 3-5 days. Lesions were made by crushing with forceps. In isolated spinal cords of animals aged 3 days, neurit es entered the crush and grew along the basal lamina of the pia mater. Growth cones with pleiomorphic appearance containing vesicles, mitoch ondria and microtubules were abundant in the marginal zone, as were sy naptoid contacts with active zones facing basal lamina. In preparation s from animals aged 11-12 days, the lesion site was disrupted and cont ained only degenerating axons, debris and vesicles. Axons and growth c ones entered the edge of the lesion but did not extend into it. Lesion s in young animals extended over distances of more than 1 mm and conta ined no radial glia. The damaged area in older preparations was restri cted to the crush site with normal astrocytes, oligodendrocytes and ne urons immediately adjacent to the lesion. Thus, similar crushes produc ed more extensive damage in younger spinal cords that were capable of regeneration than in older cords that were not. Dorsal root ganglion f ibers labeled with carbocyanine dye (DiI) were observed by video imagi ng as they grew through lesions. Individual growth cones examined subs equently by electron microscopy had grown again along pial basal lamin a. After 5 days in culture dorsal root stimulation gave rise to discha rges in ventral roots beyond the lesion indicating that synaptic conne ctions were formed by growing fibers. (C) 1996 Wiley-Liss, Inc.