Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This review summarizes the current knowledge of the biosynthesis of neurosteroids in the human brain, the enzymes mediating these reactions, their localization and the putative effects of neurosteroids. Molecular biological and biochemical studies have now firmly established the presence of the steroidogenic enzymes cytochrome P450 cholesterol side-chain cleavage (P450SCC), aromatase, 5alpha-reductase, 3alpha-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase in human brain. The functions attributed to specific neurosteroids include modulation of gamma-aminobutyric acid A (GABAA), N-methyl-d-aspartate (NMDA), nicotinic, muscarinic, serotonin (5-HT3), kainate, glycine and sigma receptors, neuroprotection and induction of neurite outgrowth, dendritic spines and synaptogenesis. The first clinical investigations in humans produced evidence for an involvement of neuroactive steroids in conditions such as fatigue during pregnancy, premenstrual syndrome, post partum depression, catamenial epilepsy, depressive disorders and dementia disorders. Better knowledge of the biochemical pathways of neurosteroidogenesis and their actions on the brain seems to open new perspectives in the understanding of the physiology of the human brain as well as in the pharmacological treatment of its disturbances.
 ...
PMID:Neurosteroid metabolism in the human brain. 1172 Aug 89

Ethanol is known to increase cortical and plasma content of GABAergic neurosteroid 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) which is responsible for some of its behavioral and electrophysiological effects. We have previously demonstrated the antidepressant like effect of 3alpha,5alpha-THP in mice. This study investigated the role of 3alpha,5alpha-THP in acute, chronic and withdrawal effects of ethanol using mouse forced swim test (FST) paradigm. While acute systemic ethanol (2 or 2.5 g/kg) administration exhibited an antidepressant like effect, its prolonged consumption produced tolerance to this effect and its withdrawal, on the other hand, elicited enhanced behavioral despair (depression). The antidepressant like effect of ethanol was potentiated by GABA(A) receptor agonist, muscimol (0.5 mg/kg, i.p.), 3alpha,5alpha-THP (0.5, 1 or 2 microg/mouse, i.c.v.) and by neurosteroidogenic drugs viz. selective serotonin reuptake inhibitor (SSRI), fluoxetine (5 or 20 mg/kg, i.p.), agonist at mitochondrial diazepam binding inhibitor receptor, FGIN 1-27 (0.5 or 1 microg/mouse, i.c.v.), or 11beta-hydroxylase inhibitor, metyrapone (0.5 or 1 microg/mouse, i.c.v.) which are known to increase endogenous 3alpha,5alpha-THP content. Furthermore, inhibition of the endogenous neurosteroid biosynthesis by drugs like 5alpha-reductase inhibitor, finasteride (50 mg/kg, s.c.), 3beta-hydroxysteroid dehydrogenase inhibitor, trilostane (30 mg/kg i.p.) or 3alpha-hydroxysteroid dehydrogenase inhibitor, indomethacin (5 mg/kg, i.p.) and GABA(A) receptor antagonist, bicuculline (1 mg/kg, i.p.) blocked the antidepressant like effect of ethanol. Withdrawal of ethanol from mice consuming it chronically displayed enhanced behavioral despair and elicited tolerance to antidepressant like action of acute ethanol (2.5, 3 or 3.5 g/kg). Moreover, sub-antidepressant doses (0.25 or 0.5 microg/mouse, i.c.v.) of 3alpha,5alpha-THP and fluoxetine (5 mg/kg, i.p.) but not imipramine (1 mg/kg, i.p.) reversed the depression associated with ethanol withdrawal indicating sensitization to their antidepressant action. Thus, 3alpha,5alpha-THP plays a pivotal role in the actions of ethanol and in the depression associated with ethanol withdrawal. These findings may be of potential ramification to contribute to the depression associated with alcoholism and its treatment using neurosteroids.
 ...
PMID:Behavioral action of ethanol in Porsolt's forced swim test: modulation by 3 alpha-hydroxy-5 alpha-pregnan-20-one. 1252 84

Concentrations of 3alpha-reduced neuroactive steroids are altered in depression and normalize after antidepressant pharmacotherapy with selective serotonin re-uptake inhibitors (SSRIs). We investigated the impact of mirtazapine on the activity of a key neurosteroidogenic enzyme, the 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD), and on the levels of neuroactive steroids in relation to clinical response. A total of 23 drug-free in-patients suffering from a major depressive episode (DSM-IV criteria) underwent 5-week treatment with mirtazapine (45 mg/day). Plasma samples were taken weekly at 0800 and quantified for neuroactive steroids by means of combined gas chromatography/mass spectrometry analysis. Enzyme activity was determined by assessment of steroid conversion rates. Irrespective of clinical outcome, there were significant increases in 3alpha,5alpha-tetrahydroprogesterone, 3alpha,5beta-tetrahydroprogesterone, 5alpha-dihydroprogesterone, and 5beta-dihydroprogesterone after mirtazapine treatment, whereas 3beta,5alpha-tetrahydroprogesterone levels were significantly decreased. In vitro investigations demonstrated a dose-dependent inhibitory effect of mirtazapine on the activity of the microsomal 3alpha-HSD in the oxidative direction (conversion of 3alpha,5alpha-tetrahydroprogesterone to 5alpha-dihydroprogesterone). Mirtazapine affects neuroactive steroid composition similarly as do SSRIs. The inhibition of the oxidative pathway catalyzed by the microsomal 3alpha-HSD is compatible with an enhanced formation of 3alpha-reduced neuroactive steroids. However, the changes in neuroactive steroid concentrations more likely reflect direct pharmacological effects of this antidepressant rather than clinical improvement in general.
 ...
PMID:Influence of mirtazapine on plasma concentrations of neuroactive steroids in major depression and on 3alpha-hydroxysteroid dehydrogenase activity. 1634 54

The neurosteroid allopregnanolone is a potent positive allosteric modulator of GABA action at GABA(A) receptors. Allopregnanolone is synthesized in the brain from progesterone by the sequential action of 5alpha-reductase type I (5alpha-RI) and 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD). 5alpha-RI and 3alpha-HSD are co-expressed in cortical, hippocampal, and olfactory bulb glutamatergic neurons and in output neurons of the amygdala, thalamus, cerebellum, and striatum. Neither 5alpha-RI nor 3alpha-HSD mRNAs is expressed in glial cells or in cortical or hippocampal GABAergic interneurons. It is likely that allopregnanolone synthesized in principal output neurons locally modulates GABA(A) receptor function by reaching GABA(A) receptor intracellular sites through lateral membrane diffusion. This review will focus on the behavioral effects of allopregnanolone on mouse models that are related to a sexually dimorphic regulation of brain allopregnanolone biosynthesis. Animal models of psychiatric disorders, including socially isolated male mice or mice that receive a long-term treatment with anabolic androgenic steroids (AAS), show abnormal behaviors such as altered fear responses and aggression. In these animal models, the cortico-limbic mRNA expression of 5alpha-RI is regulated in a sexually dimorphic manner. Hence, in selected glutamatergic pyramidal neurons of the cortex, CA3, and basolateral amygdala and in granular cells of the dentate gyrus, mRNA expression of 5alpha-RI is decreased, which results in a downregulation of allopregnanolone content. In contrast, 5alpha-RI mRNA expression fails to change in the striatum medium spiny neurons and in the reticular thalamic nucleus neurons, which are GABAergic.By manipulating allopregnanolone levels in glutamatergic cortico-limbic neurons in opposite directions to improve [using the potent selective brain steroidogenic stimulant (SBSS) S-norfluoxetine] or induce (using the potent 5alpha-RI inhibitor SKF 105,111) behavioral deficits, respectively, we have established the fundamental role of cortico-limbic allopregnanolone levels in the sexually dimorphic regulation of aggression and fear. By selectively targeting allopregnanolone downregulation in glutamatergic cortico-limbic neurons, i.e., by improving the response of GABA(A) receptors to GABA, new therapeutics would offer appropriate and safe management of psychiatric conditions, including impulsive aggression, irritability, irrational fear, anxiety, posttraumatic stress disorders, and depression.
 ...
PMID:Neurosteroid biosynthesis regulates sexually dimorphic fear and aggressive behavior in mice. 1847 73