An axotomy model for the induction of death of rat and mouse corticospinalneurons in vivo

To study trophic dependencies of rat and mouse corticospinal neurons (CSN), we established a lesion model for the induction of death of analogous popu lations of CSN in these rodent species. Before lesion, CSN were retrogradel y labeled with Fast Blue (FB). A stereotaxic cut lesion through the entire internal capsule (ICL) was used to axotomize CSN. The extent of axotomy was determined by application of a control tracer. In both species, FB-labeled CSN were localized in three major areas: (1) the sensory motor cortex; (2) the supplementary motor and medial prefrontal cortex; and (3) the somatose nsory cortex. ICL does not lead to complete axotomy of CSN of the rat and m ouse somatosensory cortex. In rats, ICL results in complete axotomy of CSN of the sensory motor cortex and incomplete axotomy of the caudal portion of the supplementary motor and medial prefrontal cortex. In mice, the area of axotomized CSN extends significantly further frontally. In both species, a xotomy-induced death of CSN is observed in the center of the sensory motor cortex. This lesion model is useful for investigations on the response of C SN of the sensory motor cortex to lesion and therapeutic drugs. (C) 2000 El sevier Science B.V. All rights reserved.