DIFFERENTIAL SPINE LOSS AND REGROWTH OF STRIATAL NEURONS FOLLOWING MULTIPLE FORMS OF DEAFFERENTATION - A GOLGI-STUDY

Golgi-Cox method and morphometric analyses were used to study the plas ticity of striatal medium spiny I neurons in B-month-old C57BL/6N mice after unilateral or bilateral lesion of the cerebral cortex or combin ed lesions of the ipsilateral cerebral cortex and intralaminar thalamu s. In adult mouse, unilateral lesions of the cerebral cortex did not r esult in a net gain or loss of linear dendritic length in a randomly s elected population of striatal medium spiny I neurons. In addition, th ere was a well-defined time course of striatal spine loss and replacem ent occurring after a unilateral cortical lesion. By day 3 postlesion the average 20-mu m dendritic segment had lost 30% of the unlesioned c ontrol spine value, reached its nadir, lost 45.5%, at 10 days postlesi on, and recovered to 80% of unlesioned control levels by 20 days postl esion. The recovery of spines was blocked by a secondary lesion on the contralateral cortex but not on the ipsilateral intralaminar thalamus . These data suggest that striatal medium spiny I neurons of adult mic e have a remarkable capacity for plasticity and reactive synaptogenesi s following a decortication. The recovery of spine density is primaril y induced by axonal sprouting of survival homologous afferent fibers f rom the contralateral cortex. (C) 1997 Academic Press.