Different effect of methylazoxymethanol on mouse cerebellar development depending on the age of injection.

Methylazoxymethanol (MAM), a powerful antimitotic, has been extensively used to affect rodent CNS development. Here we show that MAM causes different effects on mouse cerebellum depending on the age of the injected pup. Sublethal doses were determined for each age. A single injection at birth permanently reduces the number of cells. In addition, the cytoarchitecture was greatly perturbed: Purkinje cells retained an immature aspect and were dispersed through the cerebellar cortex. A single dose of MAM injected into 5 day old mice also affected the number of cells but, at the level of light microscopy, the cytoarchitecture of the cerebellar cortex appeared not to be altered. Purkinje cells, however, showed some immaturity and degenerated around the 22nd postnatal day. This modulation of MAM effect appears to provide a good model for studying cerebellar ontogeny and neuronal plasticity.