Figure 2
Cerebrospinal fluid (CSF) concentrations of kynurenic acid (KYNA) in euthymic bipolar disorder (BD) patients (data set II) and healthy controls. (a) Mean CSF KYNA concentration (±s.e.m.) in 46 healthy controls (1.60±0.10 nM), 40 bipolar patients without a history of psychosis (1.72±0.12 nM) and 36 bipolar patients with a history of psychosis (2.08±0.18 nM). One-way analysis of variance (ANOVA) with Tukey’s post hoc tests (using residuals from a linear regression of age vs CSF KYNA); P=9 × 10−3; post hoc tests: controls vs nonpsychotic bipolar patients, P=0.99; controls vs psychotic bipolar patients, P=0.015; and nonpsychotic bipolar vs psychotic bipolar patients, P=0.026. (b) CSF KYNA (nM) in the 51 bipolar patients who underwent trail making test (TMT) from Delis–Kaplan Executive Function System (D-KEFS). The mean CSF KYNA concentration was significantly higher in patients who scored below the mean standard score (<10, N=26; 2.12± 0.12 nM) compared with patients scoring average or higher (≥10, N=25; 1.62±0.21 nM, t-test: P=0.048, Pearson’s r=0.28; P=0.045). (c) The correlation between CSF KYNA and CSF homovanillic acid (HVA) (nM) in 72 of these 76 patients. Pearson’s r=0.67; P=9 × 10−11. (d) CSF HVA (nM) concentration in 72 bipolar patients with or without a history of psychosis in comparison with CSH HVA levels in 45 healthy controls. One-way ANOVA followed by Tukey’s post hoc tests revealed that the psychotic group had a significantly higher mean CSF HVA concentration (280±14.4 nM) compared with controls (216±10.6 nM, P=3 × 10−3) and nonpsychotic patients (227±15.6 nM, P=0.024), whereas no significant different in CSF HVA concentration was seen between controls and nonpsychotic patients (P=0.81). CSF KYNA concentration was independent of BD subtype (BD-I: M=1.97±0.17 nM, N=40; BD-II: M=1.80±0.13 nM, N=36, P=0.43), and did not differ by sex (M=1.93±0.15 nM among females (N=46), and M=1.82±0.15 nM among males (N=30), respectively, P=0.63). All error bars represent s.e.m. Two-sided P-values, statistical significance set to P<0.05. *P<0.05, **P<0.01, NS, not significant.
