The Impact of Pharmacological and Electric Modulation of NMDA Pathway on the Cognitive Flexibility and Volitional Movement Preparation in Patients With Parkinson's Disease

The Impact of Pharmacological and Electric Modulation of NMDA Pathway on the Cognitive Flexibility and Volitional Movement Preparation in Patients With Parkinson's Disease

The project will investigate the effect of pharmacological and electric modulation of N-methyl-D-aspartate (NMDA) pathway on the cognitive flexibility and volitional movement preparation in patients with Parkinson's disease (PD).

Sarcosine (also called N-methylglycine) is an endogenous GlyT-1 inhibitor. By blocking glycine uptake, sarcosine increases synaptic glycine concentration to enhance NMDA receptor function. NMDA receptor, a subtype of ionotropic glutamate receptors, serves important functions in the brain, including learning, memory, cognition, and neural plasticity under physiological conditions and contributes to neurodegeneration in pathophysiological processes. NMDA receptor represents collectively a group of heteromeric tetramers. Every NMDA receptor is a protein complex, typically composed of two NR1 subunits and two NR2 subunits that together form the NMDA receptor ion channel. It requires two receptor agonists (glutamate for the NR2 binding site and glycine for the NR1 binding site) to open the ion channel for NMDA receptor activation. Clinically, modulation through the NMDA-NR1-glycine site is preferred to avoid the excitotoxicity associated with the glutamate site activation.8 In addition, recent animal studies have shown that dopamine secretion can be enhanced by either blocking the striatal NR2 or by activation of the NMDA-receptor glycine site. In the project, we will focus on pharmacological enhancement of NMDA-glycine receptor function based on increasing synaptic glycine concentration by sarcosine administration to examine whether enhancing NMDA-glycine receptor activity can improve the neuropsychiatric symptoms, cognition and hopefully motor function in PD-D patients

Sarcosine is a glycine transporter-1 (GlyT-1) inhibitor. By blocking glycine uptake, sarcosine increases synaptic glycine concentration to enhance NMDA receptor function.

Outcome is defined as change in total Unified Parkinson's Disease Rating Scale (UPDRS) between the baseline to 8 weeks. The UPDRS score has three parts, part I (Mentation, Behavior and Mood), Part II (Activities of Daily Living) and Part III (Motor Examination). Each consisting of questions answered on a 0-4 point scale. The minimum total score possible is 0 and the maximum total score possible is 176. Higher scores indicating more severe symptoms.

The Cognitive Abilities Screening Instrument (CASI) has a score range of 0 to 100 and provides quantitative assessment on attention, concentration, orientation, short-term memory, long-term memory, language abilities, visual construction, list-generating fluency, abstraction, and judgment. With a higher score indicating Symptom improvement.

The CDR is a 5-point scale used to characterize six domains of cognitive and functional performance applicable to Alzheimer disease and related dementias: Memory, Orientation, Judgment & Problem Solving, Community Affairs, Home & Hobbies, and Personal Care. With a higher score indicating more severe symptoms.

The NPI scale has 12 domains: delusions, hallucinations, agitation, dysphoria, anxiety, apathy, irritability, euphoria, disinhibition, aberrant motor behavior, night-time behavior disturbances, and appetite and eating abnormalities. The total score ranges from 0 to 144, where the score for a domain is defined as the product of frequency (range: 1-4) and severity (range: 1-3). Each domain has a maximum score of 12 and with a higher score indicating more severe symptoms.

Change in Behavioral Pathology in Alzheimer's Disease Rating Scale (Behave-AD) From Baseline to 8 Weeks.

The Behave-AD includes the assessment of symptoms and a global rating of caregiver distress. A total of 25 symptoms in 7 clusters are rated: paranoid and delusional ideation, hallucinations, aggressiveness, activity disturbances, diurnal rhythm disturbances, affective disturbances and anxieties, and phobias. Caregivers rate behavioral symptoms over the preceding 2 weeks on a 0 to 3 scale. The caregiver also determines a global assessment of caregiver distress on a scale of 0 to 3. The maximum score is 75 and with a higher score indicating more severe symptoms.

The HAM-D is a 21-item rating scaled which includes an emphasis on behavioral symptoms and somatic complaints that neglects self-reported feelings of distress; and an intermingling of frequency and intensity of symptoms. The total score ranges from 0 to 64: ten items are ranked on a scale from 0 to 4; 9 items are ranked 0 to 2; and 2 items are ranked 0 to 3. With a higher score indicating more severe symptoms.

The BDI-II is a 21-item self-report questionnaire assessing the current severity of depression symptoms. Each item is scored on a scale of 0 to 3 and the total score ranges from 0 to 63. With a higher score indicating more severe symptoms.

The PDQ-39 contains 39-items covering 8 discrete dimensions: mobility, activities of daily living, emotional well-being, stigma, social support, cognitions, communication, and bodily discomfort. Each question is scored on a 5-point scale and recoded to 0 to 4 for the analysis. The total score can range from 0 to 132 and with a higher score indicating more severe symptoms.

Inclusion Criteria: The diagnosis of PD-D will be based on the criteria proposed by 2007 movement disorders PD-D task force. (Emre M et.al. Mov Disord 2007; 22:1689-1707) Exclusion Criteria: Acute confusion due to systemic illnesses or drug intoxication. Major depression Features compatible with "Probable Vascular dementia. Patient who is pregnant.

Tsai CH, Huang HC, Liu BL, Li CI, Lu MK, Chen X, Tsai MC, Yang YW, Lane HY. Activation of N-methyl-D-aspartate receptor glycine site temporally ameliorates neuropsychiatric symptoms of Parkinson's disease with dementia. Psychiatry Clin Neurosci. 2014 Sep;68(9):692-700. doi: 10.1111/pcn.12175. Epub 2014 Apr 14.