Vascular endothelial growth factor B is a growth factor that belongs to the vascular endothelial growth factor family of which VEGF-A is the best known member. In contrast to VEGF-A, VEGF-B plays a less pronounced role in the vascular system: whereas VEGF-A is important for the formation of blood vessels, such as during development or in pathological conditions, VEGF-B seems only to play in role in the maintenance of newly formed blood vessels during pathological conditions. VEGF-B plays also an important role on several types of neurons. It is important for the protection of neurons in the retina and the cerebral cortex during stroke  and of motoneurons during motor neuron diseases such as amyotrophic lateral sclerosis.VEGF-B exerts its effects via the FLT1 receptor.