Methylazoximethanol (MAM) acetate-induced cell death in the external granule cell layer of the developing cerebellum affects clusters of cells with morphological features of apoptosis. This is accompanied by selective induction of active caspase-3 expression and increased c-Jun/AP-1 (N) immunoreactivity in dying cells, as revealed with immunohistochemistry. Since the antibody to cJun/AP-1 (N) cross-reacts with epitopes emerging after caspase-mediated proteolysis during apoptosis, these results indicate that MAM-induced cell death is associated with active caspase-3 expression and function in dying cells. In order to investigate the involvement of tissue-type plasminogen activator (tPA), which has been implicated in certain forms of neuronal cell death, MAM-induced cell death has been examined in tPA-/- and tPA+/+ mice. No differences in the number of dying cells, as seen with haematoxylin and eosin staining and in situ end-labelling of fragmented nuclear DNA-processed sections, were seen between tPA-/- and tPA+/+ mice. These results indicate that tPA is not involved in MAM-induced cell death in the developing brain.
