Vascular permeability associated with axonal regeneration in the optic system of the goldfish

An association between axonal regeneration and failure of the blood-brain barrier to plasma proteins has been studied in the goldfish. Vascular permeability was examined by fluorescence microscopy following injection of rhodamine B-labelled bovine serum albumin. Axonal regeneration was studied in adjacent silver-stained sections. Following transection of axons by crushing one optic nerve, it was found that a zone of increased vascular permeability accompanied the advancing front of regenerating axons through the optic nerve, chiasma and tract and into the stratum opticum of the tectum. These observations lend support to a hypothesis in which it is postulated that axons are able to regenerate only when plasma proteins are available to their growth-cones. However, it is also possible that the increased permeability is a consequence rather than a cause of the presence of regenerated axons.