DOPAMINERGIC SPROUTING IN THE RAT STRIATUM AFTER PARTIAL LESION OF THE SUBSTANTIA-NIGRA

The capacity of the dopaminergic nerve system to reinnervate the dener vated adult striatum was analyzed in a model of partial 6-hydroxydopam ine-induced unilateral lesion of rat substantia nigra pars compacta. S prouting of dopaminergic fibers entering the ventrolateral part of the striatum from a narrow zone of the external capsule was detected on t he lesioned side 4 and 7 months, but not 10 days, after lesioning. Ult rastructural examination of the zone of sprouting revealed hypertrophi c dopaminergic fibers and growth-cone-like structures, confirming the existence of an ongoing process of spontaneous regrowth of dopaminergi c fibers. The identification of the factors involved in the regrowth o f dopaminergic fibers may help to orientate molecular research into ne w treatments for Parkinson's disease.