Objective: To explore the connection between the central dopamine system and the autonomous nervous system in GI dysfunction in PD, using animal models.

Background: Gastrointestinal (GI) dysfunction in Parkinson´s disease (PD) is characterized by motility imbalance at different levels of the GI tract often producing symptoms such as constipation, which affects the PD patient´s quality of life. Denervation of the nigrostriatal dopaminergic system, using the 6-OHDA PD rat model, suggests that the GI impairment is affected by neurotransmitter alteration. However, the pathophysiological mechanisms linking PD to enteric dysmotility needs more investigation in order to find new treatment targets for this non-motor symptom.

Methods: Rats received 6-OHDA in the median forebrain bundle (MFB). Sham-operated animals and healthy animals were used as controls. Four weeks post-lesion, proximal colon were excised and brains were collected. Circular and longitudinal smooth muscle contraction was investigated in an organ bath setup using electrical field stimulation, direct receptor stimulation with cholinergic and purinergic agents.

Results: Preliminary results suggest that the magnitude of the circular and longitudinal smooth muscle contraction were reduced in the 6-OHDA animals in comparison with controls. However, when a combination of these two muscles is studied, an intact piece of the tube, the magnitude of the contraction seems to be enhanced.

Conclusions: These data suggests a discrepancy between the excitation-contraction mechanisms within the dissected tissues which may play a role in GI dysmotility in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/smooth-muscle-dysfunction-in-the-gastrointestinal-system-in-the-6-ohda-model-of-parkinsons-disease/