Potential roles of alzheimer precursor protein A4 and β-amyloid in survival and function of aged spinal motor neurons after axonal injury

To study the potential role of Alzheimer precursor protein A4 (APP) and β-amyloid (A/β) on aging motor neuron survival, expression of APP, A/β, and choline acetyltransferase (ChaT) were investigated in aged rats after either distal axotomy or root avulsion injury. Approximately 45% in number of total aged spinal motor neuron were normally APP-positive. A/β-positive neurites were observed normally in the spinal ventral horn of aged rats. After distal axotomy, without apparent neurodegeneration such as cell loss and decreased ChaT-immunoreactivity, increased levels of APP expression were observed in the spinal cords of aged rats post-injury. In contrast, after avulsion, expression of APP and A/β were downregulated in the spinal ventral horn of aged rats, and marked loss of spinal motor neurons and downregulated ChaT expression were observed. Our data indicate that APP and A/β might play beneficial roles in neuronal survival of aged spinal motor neurons after axonal injury. © 2003 Wiley-Liss, Inc.link_to_subscribed_fulltex