[Changes in the butyrylcholinesterase activity of fenestrated capillaries in the area postrema during postnatal...

Ontogenetic changes in butyrylcholinesterase (BuChE) activity of fenestrated capillaries in the rat Area postrema lying outside of the blood-brain barrier were investigated by means of light and electron microscopic histochemical methods. Marked enzyme activity could be demonstrated in the capillary endothelial cells of the neonatal rat. The intensity of the light microscopically detectable BuChE activity in the capillaries decreased gradually during the postnatal ontogenesis, but the capacity of the enzyme synthesis of the endothelium remained unchanged in the adult rat, too. Our results do not indicate any direct correlation between BuChE positivity of capillaries and the existence of the blood-brain barrier.