The neurotrophic factors of the nerve growth factor family (neurotrophins) have been shown to promote neuronal survival after brain injury and in various models of neurodegenerative conditions. However, delivery of neurotrophins to the brain is problematic because these factors do not cross the blood-brain barrier. In addition, it has never been determined whether neurotrophin treatment results in the maintenance of function of the rescued cells. In a paper appeared in the Journal of Neuroscience (J. Neurosci. 23: 287-296, 2003), Matteo Caleo, Paolo Medini, Christopher S. von Bartheld and Lamberto Maffei, at the Institute of Neuroscience, CNR, Pisa, Italy, demonstrate that the neurotrophin brain-derived neurotrophic factor (BDNF) is transported to the brain after delivery to the eye. Following injection into the vitreous, BDNF is taken up by retinal ganglion cells, transported along the optic nerve and released to central neurons. We have found that this method of delivering BDNF is very effective in preventing the neuronal degeneration that occurs in thalamic areas following a lesion to the cerebral cortex. Indeed, one single dose of BDNF given immediately after the insult results in the saving of up to 50% of the cells that would otherwise die over a period of a few weeks. We have also measured by microelectrode recordings in vivo several physiological parameters in the lesioned animals treated with BDNF. Our data show that BDNF maintains the normal physiological responses of the rescued cells. Thus, administration of BDNF through the eye is able to rescue injured central neurons and spare their function. This preservation of function in adult damaged neurons suggests possible therapeutic applications of BDNF.
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