Most antianxiety drugs (anxiolytics) work by modulating neurotransmitters in the brain. Benzodiazepines are fast and effective anxiolytic drugs; however, their long-term use is limited by the development of tolerance and withdrawal symptoms. Ligands of the translocator protein [18 kilodaltons (kD)] may promote the synthesis of endogenous neurosteroids, which also exert anxiolytic effects in animal models. Here, we found that the translocator protein (18 kD) ligand XBD173 enhanced gamma-aminobutyric acid-mediated neurotransmission and counteracted induced panic attacks in rodents in the absence of sedation and tolerance development. XBD173 also exerted antipanic activity in humans and, in contrast to benzodiazepines, did not cause sedation or withdrawal symptoms. Thus, translocator protein (18 kD) ligands are promising candidates for fast-acting anxiolytic drugs with less severe side effects than benzodiazepines.

Context: Brain-derived neurotrophic factor (BDNF) modulates hippocampal plasticity, which is believed to be altered in patients with major depression.Objective: To examine the effect of the BDNF Val66Met polymorphism on hippocampal and amygdala volumes in patients with major depression and in healthy control subjects.Design: Cross-sectional comparison between patients and controls.Setting: Inpatients with major depression from the Department of Psychiatry and Psychotherapy and healthy controls from the community were recruited. Participants:The study population of 120 subjects included 60 patients with major depression and 60 healthy controls. Main Outcome Measures:Using a combined strategy, hippocampal and amygdala volumes were estimated on high-resolution magnetic resonance images, and genotyping was performed for the BDNF Val66Met polymorphism.Results: Patients had significantly smaller hippocampal volumes compared with controls (P = .02). Significantly smaller hippocampal volumes were observed for patients and for controls carrying the Met-BDNF allele compared with subjects homozygous for the Val-BDNF allele (P=.006). With respect to amygdala volumes, no significant differences between patients and controls and no significant main effects for the BDNF Val66Met polymorphism were observed.Conclusions: These genotype-related alterations suggest that Met-BDNF allele carriers might be at risk to develop smaller hippocampal volumes and may be susceptible to major depression. This study supports findings from animal studies that the hippocampus is involved in brain development and plasticity. Psychiatry. 2007;64:410-416 Arch Gen

Tryptophan hydroxylase (TPH), being the rate-limiting enzyme in the biosynthesis of serotonin plays a major role as candidate gene in several psychiatric disorders. Recently, a second TPH isoform (TPH2) was identified in mice, which was exclusively present in the brain. In a previous post-mortem study of our own group, we could demonstrate that TPH2 is also expressed in the human brain, but not in peripheral tissues. This is the first report of an association study between polymorphisms in the TPH2 gene and major depression (MD). We performed singlenucleotide polymorphism (SNP), haplotype and linkage disequlibrium studies on 300 depressed patients and 265 healthy controls with 10 SNPs in the TPH2 gene. Significant association was detected between one SNP (P ¼ 0.0012, global P ¼ 0.0051) and MD. Haplotype analysis produced additional support for association (Po0.0001, global P ¼ 0.0001). Our findings provide evidence for an involvement of genetic variants of the TPH2 gene in the pathogenesis of MD and might be a hint on the repeatedly discussed duality of the serotonergic system. These results may open up new research strategies for the analysis of the observed disturbances in the serotonergic system in patients suffering from several other psychiatric disorders.

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In a randomized, double-blind, placebo-controlled, multicenter study, the clinical efficacy and safety of two different extracts of St. John's wort were investigated in 147 male and female outpatients suffering from mild or moderate depression according to DSM-IV criteria. Following a placebo run-in period of three to seven days, the patients were randomized to one of three treatment groups: During the 42-day treatment period, they received 3 x 1 tablets of either placebo, Hypericum extract WS 5573 (300 mg, with a content of 0.5% hyperforin), or Hypericum extract WS 5572 (300 mg, with a content of 5% hyperforin). The manufacturing process for the two Hypericum preparations was identical, so that they differed only in their hyperforin content. Efficacy regarding depressive symptoms was assessed on days 0, 7, 14, 28, and 42, using the Hamilton Rating Scale for Depression (HAMD, 17-item version) and the Depression Self-Rating Scale (D-S) according to von Zerssen. In addition, the severity of illness was also rated by the investigators on days 0 and 42 using the Clinical Global Impression (CGI) scale. The last observation of patients withdrawn from the trial prematurely was carried forward. At the end of the treatment period (day 42), the patients receiving WS 5572 (5% hyperforin) exhibited the largest HAMD reduction versus day 0 (10.3 +/- 4.6 points; mean +/- SD), followed by the WS 5573 group (0.5% hyperforin; HAMD reduction 8.5 +/- 6.1 points) and the placebo group (7.9 +/- 5.2 points). As regards the change in the HAMD total score between day 0 and treatment end and its relationship to the hyperforin dose, a significant monotonic trend was demonstrated in the Jonckheere-Terpstra test (p = 0.017). In pairwise comparisons, WS 5572 (5% hyperforin) was superior to placebo in alleviating depressive symptoms according to HAMD reduction (Mann-Whitney U-test: p = 0.004), whereas the clinical effects of WS 5573 (0.5% hyperforin) and placebo were descriptively comparable. These results show that the therapeutic effect of St. John's Wort in mild to moderate depression depends on its hyperforin content.