Penetration of IgGs into the neuraxis of the neonatal rat.

The permeability of the mammalian blood-brain barrier to macromolecules during prenatal and postnatal development is a controversial issue. We tested the possible access of xenogeneic antibodies to the neuraxis by examining neural tissue of neonatal rats 48 h after intraperitoneal injection of rabbit IgGs, using a modification of the peroxidase-antiperoxidase (PAP) technique. The results of the present study indicate diffuse immunoreactivity for rabbit IgGs in the parenchyma in all regions of the neuraxis in neonatal rats. This work suggests that immunoglobulins, both maternal and isogeneic, may affect the nervous system during prenatal and postnatal development.

Foreign and endogenous serum protein extravasation during harmaline tremors or kainic acid seizures in the rat: a comparison.

Cerebrovascular permeability to protein (CVP-p) was assessed in rats following the systemic injection of either kainic acid (KA) or harmaline. The extravasation of a foreign (horseradish peroxidase, HRP) or an endogenous (rat immunoglobulin G, IgG) tracer protein was determined using immunohistochemical methods. During KA-induced seizures, an extravasation of both HRP and presumed IgG occurred in similar forebrain loci; a lamina-specific extravasation occurred within the dorsal hippocampus. During harmaline-induced tremors protein extravasation also occurred, but was tracer dependent. HRP reaction product was observed within the inferior olive, the cortex of the cerebellar vermis and the neocortex. However, IgG-like immunoreactivity was only detected within the circumventricular organs of harmaline-treated rats. Because KA, but not harmaline, is neurotoxic, the results are consistent with an influence of endogenous serum protein extravasation on seizure-related hippocampal damage. Possible homeostatic properties of altered CVP-p are also considered.