Chronic rotenone exposure reproduces Parkinson's disease gastrointestinal neuropathology in rats. The study found that rats exposed to chronic rotenone showed increased α-synuclein aggregates and moderate neuron loss in the enteric nervous system, as well as delayed gastrointestinal transit time, mirroring hallmarks of Parkinson's disease. The rotenone rat model provides a means to further investigate the relationship between α-synuclein aggregation, enteric neuron degeneration, and gastrointestinal dysfunction in Parkinson's disease pathogenesis.

1. Chronic rotenone exposure
reproduces Parkinson’s Disease
gastrointestinal neuropathology
Robert E. Drolet, Jason R. Cannon
Laura Montero, J. Timothy Greenamyre
BIOL 695
Meng-han Liu
9/11/2013

2. GI problems as hallmarks of PD
Cersosimo and Benarroch (2011):
• Excessive drooling
• Dysphagia
• Reduced esophageal transit ability
• Gastroparesis -- cause nausea and bloating
• Constipation--colonic motility
• Defecatory dysfunction--muscle contraction
automotive swallowing

3. Lewy bodies found in enteric nervous
system
Gradient of α-synuclein aggregates along GI tract (Beach et al.,
2010; Wakabayashi et al., 1988):
Submandibular gland &lower esophagus > stomach > small
intestine > colon >rectum.

4. Introduction:
• GI problems acting as early hallmarks of PD.
• A model is in need. (GI pathology + dysfunction)
• Rotenone model is advantageous.
Aim:
to investigate the adverse effect of chronic
rotenone exposure on the pathological and
functional deficits in enteric nervous system.

5. Materials:
23 male Lewis rats at the age of 3-
4-month-old.
Methods:
• 13 rats receive rotenone
injection five days a week for
six weeks at the concentration
of 2.0mg/kg, i.p.
• 10 rats receive vehicle alone.
• Measure rat weight all along
the experiment.

6. Enteric Nervous System:
myenteric plexus & submucosal plexus

7. Materials:
Myenteric ganglia in small
intestine.
Method:
• Pretreatment with formic
acid
• Primary antibody: mouse
anti-α-synuclein antibody.
• Secondary antibody:
biotin-labeled anti-mouse
antibody.
• Visualization: ABC (avidin-
biotin-peroxidase
complex) method.
α-synuclein immunoreactivity assay

9. Enteric neuron loss
• Material:
small intestine myenteric plexus.
• Method:
primary antibody: HuC/HuD antibody (pan-neuronal).
secondary antibody: mouse anti-HuC/HuD antibody.
laser scanning confocal microscopy.

10. GI motility assay
• Method: feed rats with CW800 Carboxylate.
• Collect feces.
• Determine CW800 content.

11. Discussion:
Rotenone model PD
Biochemistry of protein
aggregates
Serine-129 phosphorylated α-synuclein
Localization of protein
aggregates
Not restricted to one cell type.
Myenteric neuron loss observed No evidence
Delay in GI transit time observed Gastroparesis

12. • Conclusion: the adverse effects of chronic
rotenone exposure, including a delay in GI
transit time, an increase in cellular α-synuclein
aggregates and a moderate neuron cell loss in
enteric nervous system, are truly reminiscent
of hallmarks of PD.

13. Future studies
• Focus on the relationship between α-synuclein
aggregation, enteric neuron degeneration and delayed GI
transit time, and causality in between, if any.
• Expand the study onto other sections in GI tract.
• Include more behavioral endpoints.
• Identify the mechanism of delay in GI transit time.

14. Strengths
• They evaluate the long-term effect of
rotenone on enteric neurons.
• They quantify the staining assays for the ease
of comparison.
• They introduce a good model in the study of
GI tract pathology in PD.