Immunocytochemical localization of D-amino acid oxidase in rat brain

D-amino acid oxidase (D-AAO) is a peroxisomal flavoenzyme, the physiologica l substrate and the precise function of which are still unclear. We have in vestigated D-AAO distribution in rat brain, by immunocytochemistry, with an affinity-purified polyclonal antibody. Immunoreactivity occurred in both n euronal and glial cells, albeit at different densities. Glial immunostaning was strongest in the caudal brainstem and cerebellar cortex, particularly in astrocytes, Golgi-Bergmann glia, and tanycytes. Hindbrain neurons were g enerally more immunoreactive than those in the forebrain. Immunopositive fo rebrain cell populations included mitral cells in the olfactory bulb, corti cal and hippocampal neurons, ventral pallidum, and septal, reticular thalam ic, and paraventricular hypothalamic nuclei. Within the positive regions, n ot all the neuronal populations were equally immunoreactive; for example, i n the thalamus, only the reticular and anterodorsal nuclei showed intense l abelling. In the hindbrain, immunopositivity was virtually ubiquitous, and was especially strong in the reticular formation, pontine, ventral and dors al cochlear, vestibular, cranial motor nuclei, deep cerebellar nuclei, and the cerebellar cortex, especially in Golgi and Purkinje cells.