ALTERED CONNECTIONS BETWEEN NEOCORTICAL AND HETEROTOPIC AREAS IN METHYLAZOXYMETHANOL-TREATED RAT

We are currently investigating various treatments which could determin e, in the rat brain, structural abnormalities mimicking those reported in human brain dysgeneses. We can induce the formation of neuronal he terotopia in the progeny of rats by means of a double injection of the cytotoxic agent methylazoxymethanol acetate (MAM) on embryonic day 15 . We have now investigated the anatomical connections of these heterot opia by means of anterograde and retrograde tract tracing techniques. The induced heterotopia along the border of the lateral ventricles sha red common anatomical features with the periventricular nodules in hum an periventricular or subcortical nodular heterotopia (PNH). The tract tracing data demonstrated the existence of reciprocal connections bet ween the neuronal heterotopia and the ipsilateral and contralateral co rtical areas, and the presence of abnormal cortico-hippocampal and cor tico-cortical connections. On the basis of the connectivity patterns, it may be speculated that some cells in the heterotopia could be neuro ns originally committed to the cortex, that were interrupted in their migration by the MAM treatment. Given the common morphological feature s seen in human PNH and MAM-induced brain heterotopia, the anatomical and developmental analysis of MAM-treated rats may shed light on the m echanisms by which human brain dysgeneses develop in human patients. ( C) 1998 Elsevier Science B.V. All rights reserved.