An NR2B-Dependent Decrease in the Expression of trkB Receptors Precedes the Disappearance of Dopaminergic Cells in Substantia Nigra in a Rat Model of Presymptomatic Parkinson's Disease
The unilateral intrastriatal injection of 6-OHDA induces a decrease in the number of TH immunoreactive cells in SNc that is only evident 14 days after the neurotoxin injection. Photomicrographs show TH-immunoreactive (IR) cells in the contralateral (a), (c), and (e) and ipsilateral (b), (d), and (f) side of rat SN 4, 7, and 14 days after unilateral 6-OHDA intrastriatal injection, respectively. (a)–(f) scale bar = 100 μm. SNc: substantia nigra pars compacta; SNR: substantia nigra pars reticulata. (g) Percentage of TH-IR cells in the ipsilateral SNc compared to the contralateral side, at 4, 7, and 14 days after unilateral intrastriatal 6-OHDA (black columns) or ascorbic acid (sham, white columns) injections to rats. The number of cells with TH-IR signals per unit area per slice was , , and cells/mm2 in contralateral SNc of ascorbate injected rats, at 4, 7, and 14 days after treatment, respectively. In the case of 6-OHDA-treated rats, the number of cells with TH-IR signals in contralateral SNc was , , and cells/mm2, at 4, 7, and 14 days after neurotoxin injection, respectively. rats under each experimental condition. The different experimental groups were compared by a Kruskal-Wallis nonparametric ANOVA, followed by a -test. * compared with sham-treated rats.