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

Figure 4

A specific decrease in the number of positive trkB-mRNA cells is observed in ipsilateral SNc 7 days after unilateral 6-OHDA intrastriatal injections. Photomicrographs from ISH experiments show trkB-DIG positive cells in the contralateral side (a) and ipsilateral side (b) of rat SN 7 days after unilateral 6-OHDA intrastriatal injection, respectively. (a), (b) scale bar = 100 μm. SNc: substantia nigra pars compacta; SNR: substantia nigra pars reticulata. (c) Percentage of trkB-DIG positive cells in the ipsilateral SNc compared with the contralateral side, 7 days after unilateral intrastriatal 6-OHDA (black columns) or ascorbic acid (sham, white columns) injections to rats. Number of cells with trkB-DIG-positive signals in contralateral SNc was 285.7±15.9 and 317.5±31.7 cells/mm² in ascorbate and 6-OHDA injected rats, respectively. (d) Percentage of trkB-DIG positive cells in the ipsilateral SNR compared to the contralateral side, 7 days after unilateral intrastriatal 6-OHDA (black columns) or ascorbic acid (sham, white columns) injections to rats. Number of cells with trkB-DIG positive signals in contralateral SNR was 107.7±5.1 and 117.9±5.1 cells/mm² in ascorbate and 6-OHDA injected rats, respectively. 𝑛=4 rats under each experimental condition. The different experimental groups were compared with a Kruskal-Wallis nonparametric ANOVA, followed by a 𝑈-test. *𝑃<0.05 compared with sham-treated rats.

(a)

(b)

(c) Quantification of trkB-DIG labeled cells in SNc.

(d) Quantification of trkB-DIG labeled cells in SNR.