Fig. 2: Ablation of dopaminergic neurons in the VL-PAG causes hypersensitivity with accompanied reductions of Met-ENK in the spinal cord.
From: Periaqueductal grey and spinal cord pathology contribute to pain in Parkinson’s disease
a Total number of TH + cells in the ipsi- and contralateral sides of the periaqueductal grey (PAG) in sham- (n = 12) and 6-OHDA- (n = 12) PAG-lesioned rats. Representative coronal sections of the medial VL-PAG of sham and 6-OHDA lesioned rats stained for tyrosine hydroxylase with higher magnification inserts and arrows indicating representative TH + cells. b Total mean number of TH+ cells in the ipsi- and contralateral sides of the substantia nigra pars compacta (SNc). Representative coronal TH-stained sections of the caudal SNc from sham abd 6-OHDA lesioned rats. c Mean immunoreactivity intensity of Met-ENK in the dorsal horn of the spinal cord in sham and 6-OHDA-PAG-lesioned rats: each image has higher magnification images from within the dotted box. d Mechanical and thermal thresholds of sham and 6-OHDA PAG-lesioned rats on baseline, day 7, and day 14 post lesion. (i) Mechanical thresholds (ipsi; F = 35.88, P < 0.0001; contra; F = 58.62, P < 0.0001), (ii) heat thresholds (ipsi; F = 28.53, P < 0.0001; contra; F = 46.86, P < 0.0001), and (iii) cold thresholds (ipsi; F = 5.739, P < 0.0265; contra; F = 5.867, P < 0.025) were measured using the von Frey, Hargreaves, and dry-ice tests, respectively. All data are represented as mean ± SEM. Behavioural analyses were performed using a two-way ANOVA with a Tukey’s multiple comparisons test. Post-mortem histological analyses were performed using Kruskal–Wallis with Dunn’s multiple comparisons tests, * indicates that P < 0.05 comparing sham with 6-OHDA and # indicates that P < 0.05 for 6-OHDA ipsi- vs. contralateral. All scalebars = 50 µm.
