| Abstract No.: | A-C1087 |
| Country: | Canada |
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| Title: | DOPAMINE AND SEROTONIN INNERVATION OF THE STRIATUM IN PARKINSON'S AND HUNTINGTON'S DISEASES |
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| Authors/Affiliations: | 2 Catherine Bédard*; 2 Marie-Josée Wallman; 1 Martin Parent; 2 André Parent;
1 Université de Montréal, QC, Canada; 2 Université Laval, Québec, QC, Canada
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| Content: | OBJECTIVES: The primate basal ganglia receive a dense serotonin (5-HT) innervation, the anatomical and functional organization of which is poorly known compared to that of the dopamine (DA) innervation. Particularly lacking is information regarding the involvement of 5-HT in neurodegenerative diseases affecting basal ganglia. This study aims at characterizing the status of the dopamine and serotonin innervation of the striatum in Parkinson’s (PD) and Huntington’s (HD) diseases.
MATERIALS AND METHODS: An immunohistochemical approach was applied to post-mortem material gathered from patients that suffered from PD and HD and age-matched controls. The 5-HT and DA neuronal profiles were visualized with antibodies raised against the 5-HT transporter (SERT) and the DA synthesizing enzyme tyrosine hydroxylase (TH), respectively. The pattern and the density of each type of innervation were determined by a detailed microscopic scanning of coronal sections taken through anterior (pre-commissural) and posterior (post-commissural) levels of the human striatum.
RESULTS: (1) Dopamine innervation. A marked loss of TH+ fibers and axon varicosities was noted throughout most of the dorsal striatum in PD patients. This reduction was more severe at posterior than at anterior level, especially for the caudate nucleus. The number of striatal TH+ profiles at the posterior striatal level was also decreased in HD patients compared to controls. Particularly notorious was the presence of a thin (400-500 µm) but intense TH immunoreactive zone located along the ventricular border of the atrophied caudate nucleus. A similar zone was detected in controls, but it appeared much less intensely stained than in HD patients. (2) Serotonin innervation. The number of SERT+ fibers and axon varicosities was increased in PD patients compared to controls and the increase in SERT+ fibers was particularly prominent at posterior striatal level. The caudate nucleus in HD patients was found to contain more SERT+ fibers than the same structure in controls.
CONCLUSION: Our findings indicate that the dopamine and serotonin innervation of human striatum are differently affected in PD and HD, two neurodegenerative disorders characterized by opposite motor anomalies. In addition, the fact that the number of TH+ fibers decreases and that of the SERT+ increases at posterior striatal level in PD supports the hypothesis of a compensatory serotoninergic mechanism in PD.
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