11-β hydroxysteroid type 1 knockout mice display an antidepressant-like phenotype in the forced swim test.

Objective: 11β-dehydroxysteroid dehydrogenase (HSD) types 1 and 2, enzymes are involved in the activation and inactivation of glucocorticoids in vivo, respectively. Indirect evidence implicates two enzymes in the aetiology of depression but no study has directly assessed the potential role of 11 β-HSD1 in animal tests.

Methods: We assessed 11 β-HSD1 knockout mice in the forced swim test (FST), tail suspension test (TST) and for locomotor activity.

Fear-reducing effects of intra-amygdala neuropeptide Y infusion in animal models of conditioned fear: an NPY Y1 receptor independent effect.

Rationale: Neuropeptide Y (NPY) and its receptors are densely localized in brain regions involved in the mediation and modulation of fear, including the amygdala. Several studies showed that central NPY is involved in the modulation of fear and anxiety.

Objectives: In the present study, we investigated (1) whether intra-amygdala injections of NPY affect the expression of conditioned fear and (2) whether NPY Y1 receptors (Y1R) mediates the effects of these intra-amygdaloid NPY injections.

Relevance of endogenous 3alpha-reduced neurosteroids to depression and antidepressant action.

The naturally occurring 3alpha-reduced neurosteroids allopregnanolone and its isomer pregnanolone are among the most potent positive allosteric modulators of gamma-aminobutyric acid type A receptors. They play a critical role in the maintenance of physiological GABAergic tone and display a broad spectrum of neuropsychopharmacological properties. We have reviewed existing evidence implicating the relevance of endogenous 3alpha-reduced neuroactive steroids to depression and to the mechanism of action of antidepressants.

Metabotropic glutamate receptor subtype 7 ablation causes dysregulation of the HPA axis and increases hippocampal BDNF protein levels: implications for stress-related psychiatric disorders.

Regulation of neurotransmission via group-III metabotropic glutamate receptors (mGluR4, -6, -7, and -8) has recently been implicated in the pathophysiology of affective disorders, such as major depression and anxiety. For instance, mice with a targeted deletion of the gene for mGluR7 (mGluR7-/-) showed antidepressant and anxiolytic-like effects in a variety of stress-related paradigms, including the forced swim stress and the stress-induced hyperthermia tests. Deletion of mGluR7 reduces also amygdala- and hippocampus-dependent conditioned fear and aversion responses.

Chronic antidepressants reverse cerebrocortical allopregnanolone decline in the olfactory-bulbectomized rat.

Olfactory bulbectomy is one of the most validated models of depression. We demonstrate that bilateral removal of the olfactory bulbs in rats produced a significant decline of allopregnanolone content in a select cerebrocortical area which was reversed by chronic (3-week) treatment with three different classes of antidepressant (desipramine, fluoxetine, and sertraline, and venlafaxine). The effects of the chronic antidepressant treatments on allopregnanolone cortical content are observed at a time which typically coincides with the drug's abilities to reverse the behavioral deficits of the bulbectomy syndrome.

Region-specific dysregulation of allopregnanolone brain content in the olfactory bulbectomized rat model of depression.

Allopregnanolone (ALLO) is one of the most potent positive endogenous allosteric modulators of the type A gamma-aminobutyric acid (GABA(A)) receptors. While the robust anxiolytic profile of ALLO has been extensively characterized in rodents and its antidepressant-like effect was recently demonstrated in mice, there have been only few reports on alterations of brain ALLO levels in putative animal models of depression and anxiety. Removal of the olfactory bulbs of rats produces one of the most predictive animal models with which to screen for drugs with potential antidepressant activity following repeated treatment.