Abstract: The invention concerns the use of steroids and non-toxic compounds, capable of crossing the blood brain barrier characterised in that they are capable of binding the same site as pregnenolone on proteins constituting or associated with elements of the cytoskeleton and of displacing the MAP-bound pregnenolone, and of influencing the assembling and stabilisation of microtubules The invention is particularly useful for treating the nervous system, for fighting against ageing of cells containing MAPs, and for treating cancers.