Studies of endothelial mitochondrial density in degenerating rat optic nerve

The greater mitochondrial density found in blood-brain barrier endothelium has been attributed to greater utilization of energy, for tasks such as maintaining ionic homeostasis of brain extracellular fluids. To examine whether endothelial mitochondrial density changes in parallel with neural activity, we studied capillaries in rat optic nerves rendered functionless by enucleation. We found no change in endothelial mitochondrial density compared with that in contralateral control nerves. Perhaps endothelial mitochondrial density may not change in capillaries in white matter tracts, or may not ever drop below a baseline level.