Fig. 5: Dopaminergic cell reductions in the PAG and attenuated Met-ENK levels in the spinal cord are seen in Parkinson’s disease.

a Total number of TH⁺ cells in the VL-PAG of age- and sex-matched controls (n = 12) and Parkinson’s disease cases that reported spontaneous Parkinson’s disease-like pain (SPPD; n = 11) and those that did not (No SPPD; n = 15). Representative images show TH immunostain for Control (i), No SPPD (ii) and SPPD (iii) with a higher magnification image below. b Comparison of Met-ENK immunoreactivity in the dorsal horn of control (n = 10), Parkinson’s disease with pain (n = 7) and without pain (n = 9). Representative images for Met-ENK are shown for Control (i), No SPPD (ii) and SPPD (iii) with higher magnification images below. All data are expressed as mean ± SEM. All analysis were performed using Kruskal–Wallis with Dunn’s multiple tests where * indicates that P < 0.05 in comparison to control. All scalebars = 100 µm.