Islets were isolated from the pancreata of Sprague-Dawley rats and transplanted into streptozotocin-in-duced diabetic outbred Wistar rats. The effect of transplantation of islets into the cisterna magna on the diabetic state of the recipients was compared with that of the conventional transplantation of islets into liver via the portal vein. After successful intraportal (IP) transplantation, rejection took place between days 7 and 15 in all diabetic recipients. All of the eleven rats surviving after stereotaxic implantation of islets into the cisterna magna returned to normoglycemia within 7 days after transplantation. Nine of the recipients with intra-cisterna magna (IM) islet allografts were still normoglycemic at 210 days after transplantation.The glucose disappearance rate of the IM transplant rats was slower than that of the IP transplant rats, and blood glucose returned to the normal basal level within 5 hr following glucose administration. Although the in-sulin levels were almost undetectable in cerebrospinal fluid before IM transplantation, the insulin levels were markedly increased after IM transplantation and twice as great in CSF than blood. Thus, these findings indicate that the cisterna magna can serve as an immunologically privileged site for im-plantation of allogeneic pancreatic islets, and islets in CSF can regulate and maintain normal glucose homeo-stasis via secretion of insulin across the blood-brain barrier.
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