[Factors regulating survival and death of midbrain dopamine neurons]

We utilized organotypic midbrain slice cultures for the assessment of survival and degeneration of dopaminergic neurons in the substantia nigra. Application of N-methyl-D-aspartate (NMDA) to midbrain slice cultures for 24 h caused a concentration-dependent decrease in the number of surviving dopaminergic neurons visualized by tyrosine hydroxylase immunohistochemistry. Simultaneous application of (-)-deprenyl significantly attenuated the cytotoxic effect of NMDA. Because pretreatment with (-)-deprenyl failed to reduce NMDA toxicity, it is suggested that the neuroprotective effect of (-)-deprenyl is not mediated by its irreversible inhibitory action on monoamine oxidase B. We also prepared co-cultures of midbrain and striatal slices to investigate whether the presence of target tissue influences toxic actions of several drugs on dopaminergic neurons. Co-cultured dopaminergic neurons formed dense innervation to the striatal tissue. Dopaminergic neurons in midbrain--striatum co-cultures were more resistant to the cytotoxic actions of NMDA and a nitric oxide donor NOC-18, than the same neuronal population in single midbrain cultures. On the other hand, the toxicity of 1-methyl-4 phenylpyridinium ion or buthionine-[S,R]-sulfoximine was more prominent in midbrain--striatum co-cultures than that in single midbrain cultures. Organotypic slice cultures appeared to be a useful system for evaluation of dopaminergic neuronal death under experimental conditions relevant to physiological/pathophysiological situations.