The analysis of selected neurotransmitter concentrations in serum of patients with Tourette syndrome

Background and purpose Metabolic disturbances of excitatory and inhibitory neurotransmitters are implicated in pathogenesis of Tourette syndrome (TS). The aim of the study was to measure serum concentrations of glutamic acid, γ-aminobutyric acid (GABA) and glycine in TS patients and evaluate any correlation between neurotransmitter levels and age at onset, actual age, gender, tic severity, duration of the disease and concomitant psychiatric disorders. Material and methods Sixty-seven TS patients, aged 16–59, and 57 healthy controls, aged 19–37, were enrolled in the study. Information regarding medical history and physical investigation was collected using a short questionnaire. Sixty-seven percent of patients were medication-free at the time of examination and the rest had withheld treatment for 24 hours before. Blood samples were taken after a 12-hour fasting period. HPLC technique was used. Results The TS group had higher glutamic acid and lower GABA levels. Glycine concentrations were comparable. No differences regarding neurotransmitter concentrations between treated and non-treated patients were found. Patients with concomitant obsessive-compulsive disorder and severe tics had higher glutamate levels. Glutamate concentrations correlated positively with the number of comorbid psychiatric disorders and GABA concentrations correlated negatively with the number of behavioural problems in patients with comorbidities. There was no correlation between analysed neurochemicals and age, gender, age at onset or disease duration. Conclusions Imbalance between excitatory and inhibitory systems in the brains of TS patients may be reflected by glutamate and GABA serum level changes. Glutamate and GABA may be biomarkers of the disease and high concentration of glutamate may indicate more severe course of TS.