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
A decrease in the percentage of double labeling for TH and trkB in SNc is detected 7 days after unilateral 6-OHDA intrastriatal injections. Photomicrographs show TH-IF cells (a), (b) and trkB-IF cells (c), (d) in rat SNc, 7 days after unilateral 6-OHDA intrastriatal injection. (e) Merge of (a) and (c); (f) merge of (b) and (d). (a), (c), and (d) correspond to contralateral SNc while (b), (d), and (f) to ipsilateral SNc. (a)–(f) scale bar = 50 μm. SNc: substantia nigra pars compacta. (g) Quantification of cells that coexpress TH and trkB in the ipsilateral SNc compared to their contralateral side, 7 days after unilateral 6-OHDA or ascorbic acid (sham) intrastriatal injections to rats. The results were expressed as the percentage of cells that coexpress TH and trkB over the number of total TH-IF cells. Number of cells with TH-IF signals and double TH-trkB-IF signals in contralateral SNc after ascorbate injection was and cells/mm2, respectively. In the case of 6-OHDA-treated rats, number of cells with TH-IF signals and double TH-trkB-IF signals in contralateral SNc was and cells/mm2, respectively. rats for each experimental condition. The different experimental groups were compared by a Kruskal-Wallis nonparametric ANOVA, followed by a -test. * compared with sham-treated rats.