Cardiac sympathetic innervation in the MPTP non-human primate model of Parkinson disease

Purpose Systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces degeneration of dopaminergic neurons and reproduces the motor features of Parkinson disease (PD); however, the effect of MPTP on extranigral structures has been poorly studied. The aim of this research was to study the cardiac sympathetic innervation of control and MPTP-treated monkeys in order to describe the influence of MPTP toxicity on cardiac tissue. Methods Eight monkeys were included in the study and divided into two groups, four monkeys serving as controls and four forming the MPTP group. Sections from the anterior left ventricle were immunohistochemically examined to characterize the sympathetic fibers of cardiac tissue. The intensity of immunoreactivity in the nerve fibers was quantitatively analyzed using ImageJ software. Results As occurs in PD, the sympathetic peripheral nervous system is affected in MPTP-treated monkeys. The percentage of tyrosine hydroxylase immunoreactive fibers in the entire fascicle area was markedly lower in the MPTP group (24.23%) than the control group (35.27%) ( p < 0.05), with preservation of neurofilament immunoreactive fibers in the epicardium of MPTP-treated monkeys. Alpha-synuclein deposits were observed in sections of the anterior left ventricle of MPTP-treated monkeys but not in control animals, whereas phosphorylated synuclein aggregates were not observed in either controls or MPTP-treated monkeys. Conclusion The peripheral autonomic system can also be affected by neurotoxins that specifically inhibit mitochondrial complex I.