The pecten oculi of the chicken as a new in vivo model of the blood-brain barrier.

The pecten oculi of White Leghorn chicken was investigated in terms of possible blood-brain barrier properties by means of light and electron microscopy. The morphology, histochemistry and immunocytochemistry of this intraocular blood vessel convolute was examined. The permeability of the blood vessel for the electron-dense tracer lanthanum-nitrate was also determined. The endothelia of the pectinal capillaries were found to be continuous, possessing elaborate tight junctions with a high P-face association in freeze-fracture images and a low incidence of vesicles. Two barrier-specific proteins, i.e. the HT7-antigen and the glucose transporter isoform GluT-1 were specifically and exclusively expressed by the endothelial cells. Endothelial cells also showed no paracellular or transcytotic extravasation of lanthanum-nitrate. We conclude that the endothelium of the pecten oculi is the site of the blood-retina barrier. Furthermore, we demonstrate that the unique morphological characteristics of the pecten make it advantageous as a new in vivo model for the investigation of the blood-brain barrier.