[Growth of the graft and astrocytic reaction following transplantation of fetal brain to adult rat's brain. Part II: Cell suspension transplantation into the subarachnoid space].

Suspensions of basal forebrain cells of fetal rats were transplanted into the subarachnoid space of adult rats through a microsyringe needle which was transcortically inserted to the subarachnoid space. Two to 3 months after the transplantation, growth of the graft, neuritic elongation, neovascularization, and astrocytic reaction were examined by Nissl staining, histochemical staining for acethylcholinesterase and Klüver-Barrera's myelin staining, vascular relief images and immunohistochemical staining for laminin, and immunocytochemical staining for glial fibrillary acidic protein (GFAP). Transplanted fetal neurons survived and grew very well over the brain surface and exhibited facilitated neuritic elongation. Several bundles of myelinated fibers linking the subarachnoid and the subpial grafted cells were noticed, but the myelinated fibers penetrating the intact pia mater were not verified. In the grafted tissue, extracellular matrix was formed and a lot of small vessels and capillaries were noticed. Many GFAP-immunoreactive cells were seen in the graft. They had a tendency to gather perivascularly and near the margin of the graft tissue facing subarachnoid space. The subarachnoid space is thought to be an adequate place for transplanted neuronal and glial cells to grow. The subarachnoid space contains the cerebrospinal fluid and also it contacts with rich pial vessels, so that it seems to be superior to the intraparenchymal area in respects of a supply of oxygen and nutrition and of low tissue pressure. Transplanted tissue may be supposed to work as the exocrine and/or endocrine organ which secretes neurotransmitters and their synthetic enzymes and neurotrophic factors. If this is true, it would imply that the subarachnoid space is considered as a promising site for implantation.