Neocortical transplants in the mammalian brain lack a blood-brain barrier to macromolecules.
In order to determine whether the blood-brain barrier was present in transplants of central nervous tissue, fetal neocortex, which already possesses blood-brain and blood-cerebrospinal fluid barriers to protein, was grafted into the undamaged fourth ventricle or directly into the neocortex of recipient rats. Horseradish peroxidase or a conjugated human immunoglobulin G-peroxidase molecule was systemically administered into the host. These proteins were detected within the cortical transplants within 2 minutes regardless of the age of the donor or postoperative time. At later times these compounds, which normally do not cross the blood-brain barrier, inundated the grafts and adjacent host brain and also entered the cerebrospinal fluid. Endogenous serum albumin detected immunocytochemically in untreated hosts had a comparable although less extensive distribution. Thus, transplants of fetal central nervous tissue have permanent barrier dysfunction, probably due to microvascular changes, and are not integrated physiologically within the host. Blood-borne compounds, either systemically administered or naturally occurring, which should never contact normal brain tissue, have direct access to these transplants and might affect neuronal function.
D000818:Animals; D001370:Axonal Transport; D001812:Blood-Brain Barrier; D001921:Brain / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology / Q000637:transplantation*; D002552:Cerebral Ventricles / Q000502:physiology; D005260:Female; D005333:Fetus; D005865:Gestational Age; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains
D007074:Immunoglobulin G; D006735:Horseradish Peroxidase; D010544:Peroxidases