A comparison of autofluorescence emission spectra of bleached neuromelanin in non-diseased substantia nigra with spectra of other intraneuronal pigments in non-diseased and diseased tissue.

Characteristics of autofluorescence emission spectra are reported from neuromelanin autofluorescence, after paraffin wax-embedded sections of human substantia nigra were bleached by exposure to 15% hydrogen peroxide for 24 h. The characteristics of a pigment's emission spectrum probably reflect its composition, and the results are compared with autofluorescence emission spectra from examples of bleached "lipofuscin" and bleached "ceroid". (In the present study "bleached" implies that the tissue was exposed to hydrogen peroxide, whether or not a change in pigment colour was observed). The spectral characteristics of bleached neuromelanin autofluorescence were distinguished from those of bleached lipofuscin but not from examples of bleached ceroid; thus, despite similarities between neuromelanin and lipofuscin, neuromelanin resembles some examples of ceroid but not lipofuscin in respect of the properties investigated. The process of neuromelanin formation may be related to pathogenic mechanisms in the ceroidoses.