Morphological changes in serotoninergic neurites in the striatum and globus pallidus in levodopa primed MPTP treated common marmosets with dyskinesia

►Effects of MPTP or MPTP + chronic L-DOPA (LD) on 5-HT axons of primates were studied. ►MPTP led to marked striatal but not pallidal axonal 5-HT hypertrophy. ►MPTP + LD led to dyskinesia and further increases and enlargement of striatal axons. ►In dyskinesia varicosities were enlarged in pallidum but number increases were restricted only to GPe. ►In primates dyskinesia may be related to altered axonal 5-HT morphology and function.