We have determined the plasma (p) concentration of gamma-aminobutyric acid (GABA) and the dopamine metabolite homovanillic acid (HVA), and the pHVA/pGABA ratio in schizophrenic and bipolar patients. The research was undertaken in a geographic area with an ethnically homogeneous population. The HVA plasma concentrations were significantly elevated in the schizophrenic patients compared to the bipolar patients. The levels of pGABA was significantly lower in the two groups of patients compared to the control group, while the pHVA/pGABA ratio was significantly greater in the both groups of patients compared to the controls. As the levels of pHVA and pGABA are partially under genetic control it is better to compare their concentrations within an homogeneous population. The values of the ratio pHVA/pGABA are compatible with the idea of an abnormal dopamine-GABA interaction in schizophrenic and bipolar patients. The pHVA/pGABA ratio may be a good peripheral marker in psychiatric research.

We examined the catechol-O-methyl transferase (COMT) Val108/158Met genotype in 160 type 1 bipolar patients. We also analyzed the plasma concentrations of homovanillic acid (HVA), 3-methoxy-4-hydroxyphenylethylenglycol (MHPG) and 3,4-dihydroxyphenylacetic acid in 60 of those patients who had been without mood stabilizers or neuroleptic treatment for at least 8 days. Results: Patients with congruent psychotic symptoms presented a higher plasma concentration of HVA than mood incongruent psychotic patients. The Val/Val genotype was associated with higher plasma concentrations of HVA and MHPG. We detected a larger proportion of patients with psychotic symptoms in the Val/Val genotype group, although this did not reach statistical significance. It was found that the distribution of the COMT genotype was not influenced by the congruent/incongruent nature of the psychotic symptoms. Limitations: The proportion of patients without psychotic symptoms in our sample was low. This fact limits the value of some comparisons. Conclusions: Congruent and incongruent psychotic patients can be distinguished in terms of the concentration of plasma HVA. Based on the presence or absence of mood incongruent symptoms, the Val108/158Met polymorphism of the COMT gene alone does not appear to be a crucial determinant in the division of psychotic bipolar patients. Nevertheless, COMT polymorphisms may influence some of the characteristics of the patients by their effect on monoamine metabolism.

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IntroductionCertain personality traits and genetic polymorphisms are contributing factors to bipolar disorder and its symptomatology, and in turn, this syndrome influences personality. The aim of the present study is to compare the personality traits of euthymic bipolar patients with healthy controls and to investigate the effect of the catechol-O-methyltransferase (COMT) Val158Met genotype on those traits. We recruited thirty seven bipolar I patients in euthymic state following a manic episode and thirty healthy controls and evaluated their personality by means of the Cloninger’s Temperament and Character Inventory (version TCI-R-140). We assessed the influence of the polymorphism Val158Met in the COMT gene on the personality of these patients. The patients scored higher than controls in harm avoidance (61.3±12.5 vs. 55.3±8.1) and self-transcendence (45.3±12.8 vs. 32.7±8.2) and scored lower than controls in self-directedness (68.8±13.3 vs. 79.3±8.1), cooperativeness (77.1±9.1 vs. 83.9±6.5) and persistence (60.4±15.1 vs. 67.1±8.9). The novelty seeking dimension associates with the Val158Met COMT genotype; patients with the low catabolic activity genotype, Met/Met, show a higher score than those with the high catabolic activity genotype, Val/Val.ConclusionsSuffering from bipolar disorder could have an impact on personality. A greater value in harm avoidance may be a genetic marker for a vulnerability to the development of a psychiatric disorder, but not bipolar disorder particularly, while a low value in persistence may characterize affective disorders or a subgroup of bipolar patients. The association between novelty seeking scores and COMT genotype may be linked with the role dopamine plays in the brain’s reward circuits.

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