Effects of escitalopram/quetiapine combination therapy versus escitalopram monotherapy on hypothalamic-pituitary-adrenal-axis activity in relation to antidepressant effectiveness.

The hypothalamic-pituitary-adrenocortical (HPA) system is believed to play an important role in the pathophysiology of major depressive disorder. In this context, the atypical antipsychotic quetiapine (QUE) has been shown to inhibit HPA system activity in healthy subjects. In this study we investigated whether the putative inhibitory effects of QUE on HPA system activity may contribute to its antidepressant efficacy. We analyzed the effects of QUE as an augmentation to the selective serotonin reuptake inhibitor (SSRI) escitalopram (ESC) on HPA system activity in comparison to a monotherapy with ESC in relation to the antidepressant effectiveness. HPA axis activity (cortisol and ACTH) was measured by means of the dexamethasone/corticotropin-releasing hormone (DEX/CRH) test which was performed before (week 0) and during (week 1, week 5) antidepressant psychopharmacotherapy. The combination therapy, but not the ESC monotherapy showed significantly inhibiting effects on HPA system activity leading to stepwise down-regulation. ACTH concentrations were reduced in the ESC/QUE group during five weeks of treatment. The inhibitory effect of QUE maybe involved in its antidepressant effects as an augmentation strategy.

Benzodiazepines counteract rostral anterior cingulate cortex activation induced by cholecystokinin-tetrapeptide in humans.

BACKGROUND: Benzodiazepines modulate γ-aminobutyric acid type A (GABA(A)) receptors throughout the brain. However, it is not fully understood which brain regions within anxiety-related brain circuits are really responsible for their anxiolytic effects and how these regions interact. METHODS: We investigated whether the benzodiazepine alprazolam affects activity in distinct brain regions within anxiety-related circuits during an experimental anxiety paradigm by means of functional magnetic resonance imaging (fMRI). Panic symptoms were elicited by a bolus injection of the neuropeptide cholecystokinin-tetrapeptide (CCK-4) in 16 healthy male subjects in a double-blind, placebo-controlled design. Functional brain activation patterns were determined before and during the CCK-4-challenge without pretreatment and after treatment with either placebo or 1 mg alprazolam. RESULTS: The CCK-4 induced anxiety and elicited widely distributed activation patterns in anxiety-related brain circuits, especially in the rostral anterior cingulate cortex (rACC), which was attenuated after alprazolam treatment. In contrast to placebo, alprazolam abolished the activation of the rACC after challenge with CCK-4 (p<.005, corrected for multiple comparisons) and increased functional connectivity between the rACC and other anxiety-related brain regions such as amygdala and prefrontal cortex. Moreover, the reduction in the CCK-4 induced activation of the rACC correlated with the anxiolytic effect of alprazolam (r(p) = .52; p = .04). CONCLUSIONS: These findings put forward the rACC as a target for benzodiazepines and suggest that the CCK-4/fMRI paradigm might represent a human translational model for the investigation of anxiolytic drugs.

XAP2 inhibits glucocorticoid receptor activity in mammalian cells.

XAP2 is member of a protein family sharing the TPR protein interaction motif. It displays close homology to the immunophilins FKBP51 and FKBP52 that act via the Hsp90 folding machinery to regulate the glucocorticoid receptor (GR). We show that XAP2 inhibits GR by reducing its responsiveness to hormone in transcriptional activation. The effect of XAP2 on GR requires its interaction with Hsp90 through the TPR motif. The PPIase-like region turned out to be enzymatically inactive. Thus, PPIase activity is not essential for the action of XAP2 on GR, similarly to FKBP51 and FKBP52.