SEROTONERGIC SPROUTING IN PRIMATE MTP-INDUCED HEMIPARKINSONISM

Immunocytochemistry to serotonin, dopamine beta hydroxylase (DBH), and tyrosine hydroxylase (TH) was studied in the brains of 2 cebus monkey s that had developed permanent hemiparkinsonism after intracarotid inj ection of 1.2 mg N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and were sacrificed after 10-12 months. A pronounced depletion of TH-i mmunoreactive neurons was found in the substantia nigra, caudate nucle us, and putamen, ipsilaterally to the injected side. In these dopamine -denervated structures, the number of serotonergic fibers was increase d in the ipsilateral compared with the contralateral side, or with an untreated control monkey. Serotonergic neurons in the brainstem appear ed to be unaffected. Topography and number of DBH-positive fibers in t he control and the MPTP-injected sides were comparable.