Challenging the serotonergic system in Parkinson disease patients: effects on cognition, mood, and motor performance.
BACKGROUND
Parkinson disease (PD) is a neuropsychiatric disease that is characterized by motor and neuropsychiatric symptoms. Multiple neurotransmitter systems, including the serotonergic system, are involved in the pathophysiology of this disease. The exact role of the serotonergic system in PD is still unclear.


OBJECTIVE
To investigate the role of serotonin on specific aspects of cognition, mood, and motor performance in PD.


METHODS
In a double-blind, randomized, placebo-controlled, crossover design, the effects of a nonspecific serotonergic challenge with citalopram, a selective serotonin reuptake inhibitor, and a 5-HT1a receptor-specific challenge with buspirone on the Visual Verbal Learning Task, Concept Shifting Task, Profile of Mood State Questionnaire, motor section of the Unified Parkinson Disease Rating Scale (section 3), Simple Reaction Time Task, and Finger Precuing Task were studied in 21 PD patients in early stages of their disease and 21 age-, sex-, and education-matched healthy volunteers.


RESULTS
The serotonergic challenges resulted in similar effects for both groups. No changes of scores on the cognitive tasks (Visual Verbal Learning Task and Concept Shifting Task) were observed. Results of the Profile of Moods State Questionnaire indicated that, at baseline, PD patients scored less than controls on all 5 subscales. Motor performance (measured by reaction time) was negatively affected by the interventions.


CONCLUSIONS
The effects of nonspecific and 5-HT1a receptor-specific challenging of the serotonergic neurotransmitter system had similar effects in both PD patients and healthy control subjects. These findings indicate that serotonergic function is not impaired in early PD and that serotonin, although involved in the pathophysiology of PD, does not seem to play a direct role in cognition, mood, and motor performance in PD patients, but may be involved in hypokinesia.
Scholtissen
Bart
B
Institute of Brain and Behaviour, Maastricht University Hospital, Maastricht, The Netherlands. b.scholtissen@np.unimaas.nl
Verhey
Frans R J
FR
Adam
Jos J
JJ
Weber
Wim
W
Leentjens
Albert F G
AF
D000339:Affect / Q000187:drug effects*; D000368:Aged; D002065:Buspirone / Q000627:therapeutic use; D016022:Case-Control Studies; D015283:Citalopram / Q000627:therapeutic use; D003071:Cognition / Q000187:drug effects* / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010300:Parkinson Disease / Q000188:drug therapy / Q000503:physiopathology / Q000523:psychology; D011597:Psychomotor Performance / Q000187:drug effects*; D011930:Reaction Time / Q000187:drug effects; D018490:Serotonin Agents / Q000494:pharmacology* / Q000627:therapeutic use; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors; D014706:Verbal Learning / Q000187:drug effects
D018490:Serotonin Agents; D015283:Citalopram; D002065:Buspirone