Abstract:

Objective To explore the firing activity of the ventromedial thalamic nucleus（VM）in ratswith unilateral 6⁃OHDA lesions. Methods The recording electrodes were implanted in the bilateral ventromedialthalamic nucleus of SD rats via stereotactic surgery，and the stainless steel cannula for 6⁃OHDA injection was im⁃planted above the right medial forebrain bundle. The unilateral Parkinson′s disease rat model was induced by injec⁃tion of 12 μg/4 μL 6⁃OHDA into the right medial forebrain bundle. Extracellular signals in the bilateral VM wererecorded in vivo using multi ⁃channel methods before and after lesion. Tyrosine hydroxylase immunohistochemicalstaining was used to detect the damage of dopaminergic neurons in substantianigra. Cresol violet staining was usedto determine the positions of the tips of the recording electrodes. Results In model rats，the mean firing rates ofneurons in the left VM and the right VM were（15.528 7 ± 0.572 69）Hz and（5.698 1 ± 0.279 1）Hz，respectively，with significant difference（t = 15.431，P < 0.001）. Compared with that before the establishment of the model，themean firing rates of neurons in the right VM decreased significantly after the establishment of the model（F =306.701，P < 0.001）. Before and after the model′s establishment，the rates of burst firing neurons in the right VMwere 14.8 % and 44.4 %，respectively. Compared with that before the establishment of the model，the proportionof burst firing neurons in the right VM was significantly higher after the establishment of the model（P = 0.001）.Compared with that in the left VM，the proportion of burst firing neurons in the right VM increased significantly in the model rats and the difference was statistically significant（χ2 = 8.355，P = 0.004）. Conclusion In rats withunilateral 6⁃OHDA lesions，the firing activity of the ventromedial thalamic nucleus changed significantly. The ven⁃tromedial thalamic nucleus may be important in the pathophysiology of Parkinson′s disease.

Key words:

Parkinson′ s disease, ventromedial thalamic nucleus, electrophysiology, 6 ? OHDA, rats