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The role of glutamatergic dysfunction in the pathophysiology of OCD has hardly been explored despite recent reports implicating glutamatergic dysfunction in OCD. We decided to investigate CSF glutamate levels in adult OCD probands compared to psychiatrically normal controls. In total, 21 consenting psychotropic drug-naïve adult OCD patients, diagnosed using SCID-IV-CV, and 18 consenting psychiatrically normal controls with age within 10 years of age of the patients, who did not have any history of head injury or neurological illness, were included into the study. Aseptically collected and stored CSF samples obtained from the patients and control subjects were used for glutamate estimation, which was carried out by a modification of the procedure described by Lund (1986). CSF glutamate (micromol/l) level was found to be significantly higher [F(1,31)=6.846, p=0.014] in OCD patients (47.12+/-4.25) compared to control subjects (41.36+/-3.63) on analysis of covariance. There was no effect of gender, age, duration of illness, Y-BOCS score, or CGI-S score on CSF glutamate levels. Our study provides preliminary evidence implicating glutamatergic excess in the pathophysiology of OCD, which needs to be further explored by studies from other centers involving larger sample sets from different age groups.

To examine the role of noradrenergic, dopaminergic, and serotonergic mechanisms in the pathobiology of obsessive compulsive disorder (OCD) and Tourette's syndrome (TS), concentrations of tyrosine (TYR), norepinephrine (NE), 3-methoxy-4-hydroxyphenylethylene glycol (MHPG), homovanillic acid (HVA), tryptophan (TRP), and 5-hydroxyindoleacetic acid (5-HIAA) were measured in the lumbar cerebrospinal fluid (CSF) of 39 medication-free OCD patients, 33 medication-free TS patients, and 44 healthy volunteers. CSF TYR concentrations were reduced (p < .05) in the OCD patients compared to the healthy subjects. CSF NE in TS patients was 55% higher than in healthy controls (p < .001) and 35% higher than in OCD patients (p < .001). After covarying for height, CSF HVA levels were reduced (p < .05) in the OCD group compared to TS patients but not compared to the normal volunteers. No mean differences in CSF MHPG, TRP, and 5-HIAA were observed in this study across the three groups. The CSF NE data support the hypothesis that noradrenergic mechanisms are involved in the pathobiology of TS. Alterations in the balance of noradrenergic, dopaminergic, and serotonergic systems are likely involved in the pathobiology of OCD.