Toxic equine parkinsonism: an immunohistochemical study of 10 horses with nigropallidal encephalomalacia.

This research aims to understand the brain condition Nigropallidal Encephalomalacia (NPE) in horses caused by chronic ingestion of certain plants, and to identify if it carries any similarity to human Parkinson’s disease. It finds that while the affected regions in the brain are partly identical, the pathology differs and suggests NPE could be a model for a form of Parkinson’s caused by environmental toxins.

Study Goal and Methodology

• The main purpose of this study is to revisit the pathological alterations of Nigropallidal Encephalomalacia (NPE) in horses and to conduct an immunohistochemistry study. This study will help to understand the similarity of NPE in horses with human Parkinson’s disease.
• To accomplish this, the researchers chose to analyze the horse brain using antibodies to two substances – tyrosine hydroxylase and α-synuclein.
• Tyrosine hydroxylase is used as a marker for dopaminergic neurons (neurons that produce dopamine, a neurotransmitter that plays a key role in motor control function).
• α-synuclein is a protein that, in humans, is abundantly present in the brain where it is associated with neurodegenerative diseases like Parkinson’s. It forms the main component of pathologic inclusions called ‘Lewy bodies’ which are a characteristic of Parkinson’s.

Findings and Interpretation

• The study discovered that NPE lesions in horses are situated within the substantia nigra pars reticulata and the front part of the globus pallidus. However, the cell bodies of the dopaminergic neurons in the substantia nigra pars compacta remained unaffected.
• Furthermore, they found that the NPE in horses cause partial damage to the dopaminergic fibers passing through the globus pallidus, but no Lewy bodies were detected.
• This indicates that while the NPE affects regions in the horse brain which also play key roles in human Parkinson’s disease, it does not affect the dopaminergic neurons nor does it cause the formation of Lewy bodies, distinguishing it from human Parkinson’s disease.
• Despite these differences, the study still suggests that the horse NPE might serve as a large animal model for a form of Parkinson’s that is acquired from environmental toxins, due to its effect on the globus pallidus and substantia nigra pars reticulata.