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Alterations in dopamine neurotransmission and disturbed norepinephrine activity have been implicated in the pathogenesis of schizophrenia. We considered the dopamine-beta-hydroxylase (DBH) gene located on the long arm of chromosome 9 (9q34.3) as a candidate gene for schizophrenia. DBH catalyzes the synthesis of norepinephrine from dopamine in noradrenergic neurons. In addition to DBH we used in the linkage study DNA markers ABL (centromeric) and D9S114 (telomeric). The aim of this study was to test linkage and association between PCR-based genotyped markers and schizophrenia. A simulation was done to investigate the power of our sample. In 34 Austrian families we could not detect linkage between schizophrenia and schizophrenia spectrum disorders and the three genetic markers. We could not find any significant deviation in allelic or genotypic distribution from expectations. Based on our results we conclude that the DBH gene seems to have no strong contribution in the etiology of schizophrenia.

The aim of the investigation was to test genes for predisposition to bipolar affective disorder. Therefore, we studied candidate genes in a sample of unrelated patients (n = 102) and healthy controls (n = 79) of Austrian origin, searching for a possible association between polymorphic DNA markers of 5 candidate genes (serotonin transporter, 5-HTT; serotonin 2a receptor, 5-HT2a; dopamine D2 receptor, DRD2; dopamine D3 receptor, DRD3; dopamine transporter, DAT1) and bipolar disorder. There was an association between allelic and genotypic frequencies of 5-HTT and affection status (p = 0.014 and p = 0.017, respectively). However, after correction for multiple comparisons (Bonferroni), these results did not remain significant. Nevertheless, the findings might suggest that alterations in the structure of 5-HTT are involved in the pathogenesis of bipolar disorder, which could have major implications in treatment. No association between 5-HT2a, DRD2, DRD3, DAT1 and bipolar disorder was found.