Serotonergic hyperinnervation into the dopaminergic denervated striatum compensates for dopamine conversion from exogenously administered l-DOPA.

The aim of this study was to determine whether raphe-striatal serotonergic neurons of adult rats with extensive nigro-striatal dopaminergic denervation are induced by injection of exogenous L-DOPA to contain dopamine. Double-labeling immunofluorescence study was conducted. In the lesioned striatum of rats that received L-DOPA, serotonergic hyperinnervation was observed, and dopamine was detected in serotonergic varicose fibers. These findings suggest that striatal serotonergic hyperinnervation can compensate for the lost function of dopaminergic neurons.