Brainstem Modulates Parkinsonism-Induced Orofacial Sensorimotor Dysfunctions.

Area of Science:

• Neuroscience
• Muscle Physiology
• Pharmacology

Background:

• Parkinson's Disease (PD) involves motor and non-motor orofacial symptoms.
• L-DOPA is a primary treatment, but can induce side effects like dyskinesia.
• The trigeminal system and jaw muscles are implicated in PD orofacial manifestations.

Purpose of the Study:

• Investigate pathophysiologic mechanisms of lateral pterygoid muscles (LPMs) and trigeminal system in PD.
• Analyze PD-induced orofacial changes and L-DOPA-induced dyskinesia effects.
• Correlate neural activation with muscle and pain responses.

Main Methods:

• Created a unilateral 6-hydroxydopamine-induced hemiparkinsonian rat model.
• Assessed motor (dyskinesia) and nociceptive responses.
• Analyzed Fos-B, glial cells, and muscle fiber morphology in trigeminal nuclei and LPMs.

Main Results:

• Hemiparkinsonian and dyskinetic rats showed increased hyperalgesia.
• LPMs showed altered myosin fibers, glycolytic metabolism, and inflammatory markers in dyskinetic rats.
• Increased Fos-B expression and glial activation were observed in specific brain nuclei contralateral to the lesion.

Conclusions:

• Spinal trigeminal nucleus activation links to orofacial sensory impairment in PD rats.
• L-DOPA-induced dyskinesia may involve LPM fatigue and activation of motor/facial nuclei.
• Findings highlight the complex interplay between PD, L-DOPA, and orofacial function.