The ultrastructural distribution of alpha-synuclein-like protein in normal mouse brain

The synaptic protein alpha-synuclein is found throughout the brain, although its function remains ill-defined. Abnormal accumulations of alpha-synuclein have been recognised to be associated with a number of neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Nevertheless, little is known about the precise localisation of this protein within the normal brain, information which might contribute to our understanding of its role in both health and disease. We raised an antibody which recognises both human and murine alpha-synuclein and this was used to study the distribution of the protein in the normal mouse brain. We used morphological characteristics to classify the immunopositive presynaptic elements and their targets. We conclude that the protein is present in synaptic boutons of axons with different neurochemical phenotypes but that it is not present in all synaptic terminals. Furthermore, the protein is present in the terminals of neurons such as the dopaminergic neurons of the substantia nigra and the glutamatergic neurons of the hippocampus, cell types which accumulate alpha-synuclein in disease. Nevertheless alpha-synuclein is also found in terminals of neurons which have not been reported to accumulate the protein in neurodegenerative disorders.