A study of the expression of laminin in the spinal cord of the frog during development and regeneration.

In the present experiments, we have used an affinity-purified polyclonal antibody to laminin to determine the time course of expression of laminin in the central nervous system (CNS) of Rana temporaria tadpoles during normal development and during restoration of the dorsal columns of the spinal cord. Immunoblotting analysis indicated that in the peripheral nervous system (PNS) of adult frogs the antibody recognized proteins of molecular weights 350-400 and 205-220 kDa, corresponding to the A and B chains respectively of mammalian laminin. Immunohistochemistry with our antibody suggested that laminin was absent from the tadpole spinal cord, and did not appear even in the basal lamina of the blood vessels within the spinal cord until after metamorphosis. Furthermore, there was no evidence of laminin expression in the dorsal columns after hemisection of the spinal cord. However, throughout development laminin was present in basal lamina outside the CNS, in particular in the pial membranes, and in the basal lamina of blood vessels and sheath cells in the dorsal and ventral roots. Electron microscopy showed that the blood vessels of CNS capillaries had basal laminae throughout development that was morphologically indistinguishable from that seen in peripheral vessels.