[Abstract Title]. - Society for Neuroscience

Abstract: 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. 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), middle (commissural) and
posterior (post-commissural) levels of the human striatum. 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 middle level, especially for the caudate nucleus. The
number of striatal TH+ profiles was also decreased in HD patients compared to controls, with a
more profound loss in the caudate nucleus. 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. Serotonin innervation: The number of SERT+ fibers and
axon varicosities was increased in PD patients compared to controls. The caudate nucleus in HD
patients appeared to contain more SERT+ fibers than the same structure in controls while the
nucleus accumbens contained a decreased number of theses fibers compared to controls. 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 increase in SERT+ fibers in PD supports the hypothesis of a
compensatory serotoninergic mechanism in PD.
Disclosures: C. Bedard, None; M. Wallman, None; A. Parent, None; M. Parent, None.
Poster
273. Basal Ganglia: Transmitters and Neuromodulation I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 273.2/II17
Topic: D.15.a. Transmitters and neuromodulation
Support: United States Public Health grant NS 047452 (ARW)
NARSAD