Neuroactive Steroids In Plasma Research Articles

Disability progression in multiple sclerosis is associated with plasma neuroactive steroid profile.

Neuroactive steroids (NASs) exert multiple biological effects on development and inflammation. The effects of NASs on disease progression in multiple sclerosis (MS) are uncertain, prompting analyses of NAS profiles during the transition from clinically isolated syndrome (CIS) to relapsing-remitting (RR) MS. Subjects with CIS or RRMS and healthy controls (HCs) were recruited; demographic and clinical data as well as disability scores measured by the Expanded Disability Status Scale (EDSS) were recorded. Matched plasma NAS and amino acid (AA) concentrations were measured. HC (n = 17), CIS (n = 31), and RRMS (n = 33) groups showed similar ages and sex distribution although disability scores were higher in the RRMS group. The conversion rate of CIS to RRMS group was 51.6% (n = 16) during a mean follow-up period of 1.85 years. The RRMS group showed significantly higher mean allopregnanolone, aspartate, and taurine concentrations with lower epiallopregnanolone concentrations than CIS patients, and higher L-serine-O-phosphate and lower alanine, arginine, and glutamine concentrations than the HC group. Among CIS and RRMS groups, multivariate hierarchical regressions revealed that higher concentrations of plasma tetrahydrodeoxycorticosterone (THDOC) may predict disability worsening. RRMS and CIS patients exhibited differing concentrations of both NASs and AAs in plasma while both THDOC and pregnanolone might serve as biomarkers of disability worsening.

Resting-state functional connectivity, cortical GABA, and neuroactive steroids in peripartum and peripartum depressed women: a functional magnetic resonance imaging and spectroscopy study

Postpartum depression (PPD) is associated with abnormalities in resting-state functional connectivity (RSFC) but the underlying neurochemistry is unclear. We hypothesized that peripartum GABAergic neuroactive steroids (NAS) are related to cortical GABA concentrations and RSFC in PPD as compared to healthy comparison women (HCW). To test this, we measured RSFC with fMRI and GABA+/Creatine (Cr) concentrations with proton magnetic resonance spectroscopy (1H MRS) in the pregenual anterior cingulate (pgACC) and occipital cortices (OCC) and quantified peripartum plasma NAS. We examined between-group differences in RSFC and the relationship between cortical GABA+/Cr concentrations with RSFC. We investigated the relationship between NAS, RSFC and cortical GABA+/Cr concentrations. Within the default mode network (DMN) an area of the dorsomedial prefrontal cortex (DMPFC) had greater connectivity with the rest of the DMN in PPD (peak voxel: MNI coordinates (2, 58, 32), p = 0.002) and was correlated to depression scores (peak HAM-D17 voxel: MNI coordinates (0, 60, 34), p = 0.008). pgACC GABA+/Cr correlated positively with DMPFC RSFC in a region spanning the right anterior/posterior insula and right temporal pole (r = +0.661, p = 0.000). OCC GABA+/Cr correlated positively with regions spanning both amygdalae (right amygdala: r = +0.522, p = 0.000; left amygdala: r = +0.651, p = 0.000) as well as superior parietal areas. Plasma allopregnanolone was higher in PPD (p = 0.03) and positively correlated with intra DMPFC connectivity (r = +0.548, p = 0.000) but not GABA+/Cr. These results provide initial evidence that PPD is associated with altered DMN connectivity; cortical GABA+/Cr concentrations are associated with postpartum RSFC and allopregnanolone is associated with postpartum intra-DMPFC connectivity.

Treatment of male rats with finasteride, an inhibitor of 5alpha-reductase enzyme, induces long-lasting effects on depressive-like behavior, hippocampal neurogenesis, neuroinflammation and gut microbiota composition

Persistent alteration of plasma neuroactive steroid levels associated with major depression has been recently reported in men after the suspension of the treatment for androgenetic alopecia with finasteride, an inhibitor of the enzyme 5alpha-reductase. Observations in male rats confirmed persistent alterations in neuroactive steroid levels also in the brain. In the present study, we have ascertained possible effects on depressive-like behavior, neurogenesis, gliosis, neuroinflammation and gut microbiota in male rats after subchronic treatment for 20 days with finasteride and after one month of its withdrawal. At the end of treatment there was an increase in the number of pH3 immunoreactive cells in the subgranular zone of the dentate gyrus together with an increase in the mRNA levels of TNF-α in the hippocampus. By one month after the end of finasteride treatment, rats showed depressive-like behavior coupled with a decrease in the number of pH3 immunoreactive cells in the subgranular zone of the dentate gyrus, a decrease in granule cell density in the granule cell layer and an increase in the number of GFAP immunoreactive astrocytes in the dentate gyrus. Finally, alteration of gut microbiota (i.e., an increase in Bacteroidetes phylum and in Prevotellaceae family at the end of the treatment and a decrease in Ruminococcaceae family, Oscillospira and Lachnospira genus at the end of the withdrawal period) was detected.In conclusion, finasteride treatment in male rats has long term effects on depressive-like behavior, hippocampal neurogenesis and neuroinflammation and gut microbiota composition.

Peripartum neuroactive steroid and γ-aminobutyric acid profiles in women at-risk for postpartum depression

Neuroactive steroids (NAS) are allosteric modulators of the γ-aminobutyric acid (GABA) system. NAS and GABA are implicated in depression. The peripartum period involves physiologic changes in NAS which may be associated with peripartum depression and anxiety. We measured peripartum plasma NAS and GABA in healthy comparison subjects (HCS) and those at-risk for postpartum depression (AR-PPD) due to current mild depressive or anxiety symptoms or a history of depression. We evaluated 56 peripartum medication-free subjects. We measured symptoms with the Hamilton Depression Rating Scale (HAM-D17), Hamilton Anxiety Rating Scale (HAM-A) and Spielberger State-Trait Anxiety Inventory-State (STAI-S). Plasma NAS and GABA were quantified by liquid chromatography-mass spectrometry. We examined the associations between longitudinal changes in NAS, GABA and depressive and anxiety symptoms using generalized estimating equation methods. Peripartum GABA concentration was 1.9±0.7ng/mL (p=0.004) lower and progesterone and pregnanolone were 15.8±7.5 (p=0.04) and 1.5±0.7ng/mL (p=0.03) higher in AR-PPD versus HCS, respectively. HAM-D17 was negatively associated with GABA (β=−0.14±0.05, p=0.01) and positively associated with pregnanolone (β=0.16±0.06, p=0.01). STAI-S was positively associated with pregnanolone (β=0.11±0.04, p=0.004), allopregnanolone (β=0.13±0.05, p=0.006) and pregnenolone (β=0.02±0.01, p=0.04). HAM-A was negatively associated with GABA (β=−0.12±0.04, p=0.004) and positively associated with pregnanolone (β=0.11±0.05, p=0.05). Altered peripartum NAS and GABA profiles in AR-PPD women suggest that their interaction may play an important role in the pathophysiology of peripartum depression and anxiety.

Effects of electroconvulsive therapy on plasma levels of neuroactive steroids in inpatients with major depression

Objectıve. Neuroactive steroids (NAS) are neuroactive molecules that have been shown to be associated with various psychiatric disorders. There are some inconclusive findings about the alteration in neuroactive steroid levels after the treatment of depression and ECT is still one of the most effective treatment choices for treatment resistant depression. Thus, we aimed to investigate the alterations of several NAS in plasma after ECT in inpatients with treatment resistant depression. Methods. In this study we enrolled 19 consecutive patients, 12 female and 7 male inpatients with major depression, who were not responding to medication, for whom ECT was Indicated, and were not taking any antidepressant treatment for at least a week prior to enrolment. We measured plasma progesterone, testosterone, pregnenolone, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate, and estradiol levels before and after ECT. Results. The mean age of the participants was 38.3 ± 9.4 years. The mean plasma neuroactive steroid levels were insignificant between baseline and post ECT in patients with treatment resistant depression. Conclusıons. ECT does not seem to influence plasma neuroactive steroid levels in patients with treatment resistant depression. Additionally, plasma dehydroepiandrosterone and pregnenolone levels might be associated with improvement in depressive symptoms after ECT.

Quantification of ten neuroactive steroids in plasma in Withdrawal Seizure-Prone and -Resistant mice during chronic ethanol withdrawal.

The rapid membrane actions of neuroactive steroids, particularly via an enhancement of γ-aminobutyric acidA receptors (GABAARs), participate in the regulation of central nervous system excitability. Prior evidence suggests an inverse relationship between endogenous GABAergic neuroactive steroid levels and behavioral changes in excitability during ethanol withdrawal. Previously, we found that ethanol withdrawal significantly decreased plasma allopregnanolone (ALLO) levels, a potent GABAergic neuroactive steroid, and decreased GABAAR sensitivity to ALLO in Withdrawal Seizure-Prone (WSP) but not in Withdrawal Seizure-Resistant (WSR) mice. However, the effect of ethanol withdrawal on levels of other endogenous GABAAR-active steroids is not known. After validation of a gas chromatography-mass spectrometry method for the simultaneous quantification of ten neuroactive steroids, we analyzed plasma from control male WSP-1 and WSR-1 mice and during ethanol withdrawal. We quantified levels of nine neuroactive steroids in WSP-1 and WSR-1 plasma; levels of pregnanolone were not detectable. Basal levels of five neuroactive steroids were higher in WSR-1 versus WSP-1 mice. Ethanol withdrawal significantly suppressed five neuroactive steroids in WSP-1 and WSR-1 mice, including ALLO. Due to lower basal levels of some GABAAR-active steroids in WSP-1 mice, a withdrawal-induced decrease in WSP-1 mice may have a greater physiological consequence than a similar decrease in WSR-1 mice. Because WSP-1 mice also exhibit a reduction in GABAAR sensitivity to neuroactive steroids during withdrawal, it is possible that the combined decrease in neuroactive steroids and GABAAR sensitivity during ethanol withdrawal in WSP-1 mice represents a neurochemical substrate for severe ethanol withdrawal.

Comparison of plasma and cerebrospinal fluid levels of neuroactive steroids with their brain, spinal cord and peripheral nerve levels in male and female rats

Physiological changes and pathological alterations in the nervous system of rodents are associated with modifications in the levels of neuroactive steroids in the brain, spinal cord and/or peripheral nerves. Measures of tissue levels of steroids in the nervous system present serious limitations for human studies and for longitudinal studies in animals. In this study we have explored whether levels of neuroactive steroids in plasma and the cerebrospinal fluid reflect their levels in neural tissues. To this aim, we have evaluated by liquid chromatography-tandem mass spectrometry the levels of several neuroactive steroids in plasma, cerebrospinal fluid, cerebral cortex, cerebellum, hippocampus, spinal cord and sciatic nerve of male and female rats. Data indicate that plasma and cerebrospinal fluid levels of steroids do not fully reflect their tissue levels. However, the interindividual variations in the levels of all the steroids assessed, with the exception of dehydroepiandrosterone, showed a positive correlation in plasma and cerebral cortex. Most steroids also showed a positive correlation in plasma and the cerebellum, the spinal cord and the sciatic nerve. In the hippocampus, the levels of tetrahydroprogesterone, testosterone and testosterone metabolites showed a significant positive correlation with their respective levels in plasma. The cerebrospinal fluid levels of some steroids, such as testosterone and dihydrotestosterone, showed a full correlation with tissue levels. In addition, cerebrospinal fluid levels of pregnenolone, progesterone, and 17β-estradiol showed a positive correlation with their corresponding levels in the majority of the neural structures analyzed. These findings suggest that the levels of some neuroactive steroids in cerebrospinal fluid as well as in plasma may be valuable to predict their levels in the nervous system.

GABAergic neuroactive steroids and resting-state functional connectivity in postpartum depression: A preliminary study

Postpartum depression (PPD) affects up to 1 in 8 women. The early postpartum period is characterized by a downward physiological shift from relatively elevated levels of sex steroids during pregnancy to diminished levels after parturition. Sex steroids influence functional brain connectivity in healthy non-puerperal subjects. This study tests the hypothesis that PPD is associated with attenuation of resting-state functional connectivity (rs-fc) within corticolimbic regions implicated in depression and alterations in neuroactive steroid concentrations as compared to healthy postpartum women. Subjects (n = 32) were prospectively evaluated during pregnancy and in the postpartum with repeated plasma neuroactive steroid measurements and mood and psychosocial assessments. Healthy comparison subjects (HCS) and medication-free subjects with unipolar PPD (PPD) were examined using functional magnetic resonance imaging (fMRI) within 9 weeks of delivery. We performed rs-fc analysis with seeds placed in the anterior cingulate cortex (ACC), and bilateral amygdala (AMYG), hippocampi (HIPP) and dorsolateral prefrontal cortices (DLPFCs). Postpartum rs-fc and perinatal neuroactive steroid plasma concentrations, quantified by liquid chromatography/mass spectrometry, were compared between groups. PPD subjects showed attenuation of connectivity for each of the tested regions (i.e. ACC, AMYG, HIPP and DLPFC) and between corticocortical and corticolimbic regions vs. HCS. Perinatal concentrations of pregnanolone, allopregnanolone and pregnenolone were not different between groups. This is the first report of a disruption in the rs-fc patterns in medication-free subjects with PPD. This disruption may contribute to the development of PPD, at a time of falling neuroactive steroid concentrations.

Alcohol exposure during late adolescence increases drinking in adult Wistar rats, an effect that is not reduced by finasteride.

We tested whether an exposure to alcohol in late adolescence, an age of rapid increase in neuroactive steroid precursors, would increase voluntary alcohol consumption in adult rats and whether this effect would be modulated by finasteride, an inhibitor of neuroactive steroid synthesis. In Experiment 1, we exposed male Wistar rats to 8% alcohol during the dark cycle for 1 week during late adolescence [postnatal days (PNDs) 51-58], and then measured voluntary alcohol consumption 1 month later in adulthood (PNDs 91-104). In Experiment 2, finasteride was administered during the forced alcohol exposure in late adolescence and, in Experiment 3, during voluntary alcohol consumption in adulthood. Plasma was collected at the end of each finasteride treatment to confirm the reduction of plasma neuroactive steroid levels. We found that a daily 12-h exposure to alcohol for 7 days in late adolescence significantly increased voluntary alcohol consumption (4-fold) a month later during adulthood. Finasteride administration in late adolescence increased group alcohol intake in late adolescence but did not block the effect of adolescent alcohol exposure on increasing alcohol preference in adulthood. There was no effect of finasteride treatment in adulthood on alcohol preference. A daily 12-h exposure to alcohol for 7 days in late adolescence was sufficient to induce chronically increased alcohol preference in adulthood, indicating that this age may be sensitive to the effects of alcohol.

Relationship between omega-3 fatty acids and plasma neuroactive steroids in alcoholism, depression and controls

Deficiency in the long-chain ω-3 fatty acid, docosahexaenoic acid (DHA) has been associated with increased corticotropin releasing hormone and may contribute to hypothalamic pituitary axis (HPA) hyperactivity. Elevated levels of the neuroactive steroids, allopregnanolone (3 α,5 α-THP) and 3 α,5 α-tetrahydrodeoxycorticosterone (THDOC) appear to counter-regulate HPA hyperactivity. Plasma essential fatty acids and neurosteroids were assessed among 18 male healthy controls and among 34 male psychiatric patients with DSM-III alcoholism, depression, or both. Among all subjects, lower plasma DHA was correlated with higher plasma THDOC ( r=−0.3, P<0.05) and dihydroprogesterone (DHP) ( r=−0.52, P<0.05). Among psychiatric patients lower DHA was correlated with higher DHP ( r=−0.60, P<0.01), and among healthy controls lower plasma DHA was correlated with higher THDOC ( r=−0.83, P<0.01) and higher isopregnanolone (3 β,5 α-THP) ( r=−0.55, P<0.05). In this pilot observational study, lower long-chain ω-3 essential fatty acid status was associated with higher neuroactive steroid concentrations, possibly indicating increased feedback inhibition of the HPA axis.

A decrease in the plasma DHEA to cortisol ratio during smoking abstinence may predict relapse: a preliminary study

Increases in depressive symptoms during smoking cessation have been associated with risk for relapse. Several studies have linked plasma levels of cortisol and dehydroepiandrosterone (DHEA) or DHEA-sulfate (DHEAS) to depressive symptoms. To determine whether changes in plasma cortisol, DHEA, or DHEAS levels and emergence of depressive symptoms during smoking cessation are associated with smoking relapse. Subjects were healthy non-medicated men and women, aged 39+/-12 years, who smoked, on average, 22 cigarettes per day. Depressive symptoms, smoking withdrawal symptoms, and plasma steroid levels were measured before and after 8 days of verified smoking abstinence. Relapse status at day 15 was then determined. In the full sample (n=63), there was a trend for changes in depressive symptoms to be associated with relapse. In the subset of 25 subjects with plasma neuroactive steroid data, there was a significant interaction between the change in the plasma DHEA/cortisol ratio from day 0 to day 8 and relapse status at day 15. This ratio was similar before abstinence, but lower at day 8 in relapsed, compared to abstinent, subjects. Changes in the DHEA/cortisol ratio tended to predict changes in depressive symptoms in the women only. A decrease in the plasma DHEA/cortisol ratio during 8 days of smoking abstinence was associated with relapse over the following week. Further research is needed to fully characterize sex-specific relationships between abstinence-induced changes in neuroactive steroid levels, depressive or withdrawal symptoms, and relapse. Such research may lead to new interventions for refractory smoking dependence.

Relevance of endogenous 3α-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. A wide range of preclinical and clinical evidence suggesting the antidepressant potential of 3alpha-reduced neuroactive steroids and a possible involvement of a deficiency and a disequilibrium of neuroactive steroid levels in pathomechanisms underlying the etiology of major depressive disorder have emerged in recent years. Antidepressants elevate 3alpha-reduced neurosteroid levels in rodent brain, and clinically effective antidepressant pharmacotherapy is associated with normalization of plasma and cerebrospinal fluid (CSF) concentrations of endogenous neuroactive steroids in depressed patients, unveiling a possible contribution of neuroactive steroids to the mechanism of action of antidepressants. In contrast, recent studies using nonpharmacological antidepressant therapy suggest that changes in plasma neuroactive steroid levels may not be a general mandatory component of clinically effective antidepressant treatment per se, but may reflect distinct properties of pharmacotherapy only. While preclinical studies offer convincing evidence in support of an antidepressant-like effect of 3alpha-reduced neuroactive steroids in rodent models of depression, current clinical investigations are inconclusive of an involvement of neuroactive steroid deficiency in the pathophysiology of depression. Moreover, clinical evidence is merely suggestive of a role of neuroactive steroids in the mechanism of action of clinically effective antidepressant therapy. Additional clinical studies evaluating the impact of successful pharmacological and nonpharmacological antidepressant therapies on changes in neuroactive steroid levels in both plasma and CSF samples of the same patients are necessary in order to more accurately address the relevance of 3alpha-reduced neuroactive steroids to major depressive disorder. Finally, proof-of-concept studies with drugs that are known to selectively elevate brain neurosteroid levels may offer a direct assessment of an involvement of neurosteroids in the treatment of depressive symptomatology.

Structure−Activity Relationships and Effects on Neuroactive Steroid Synthesis in a Series of 2-Phenylimidazo[1,2-a]pyridineacetamide Peripheral Benzodiazepine Receptors Ligands

A series of 36 imidazopyridineacetamides (2-37) were designed and synthesized to evaluate the effects of structural changes on the amide nitrogen at both central (CBRs) and peripheral benzodiazepine receptors (PBRs). These changes include variations in the length and number of the alkyl groups as well as introduction of different aromatic, heteroaromatic, and conformationally constrained groups. The affinities of these compounds for CBRs and PBRs were determined, and the results indicate that bulkiness of the substituents, their branching, and length beyond an optimal value may cause hindrance to the ligand in its interaction with the receptor. The presence of aromatic or conformationally constrained substituents on the carboxamide nitrogen can be conducive to high affinity and selectivity. Furthermore, the ability of a subset of the most active ligands to stimulate synthesis of neuroactive steroids in plasma and brain was evaluated in vivo and in vitro. Compound 3 exhibited very marked effects on the peripheral and central synthesis of neuroactive steroids, while 36 (potent at subnanomolar level) showed a slight ability to affect neuroactive steroid content in the cerebral cortex.

Brain steroidogenesis mediates ethanol modulation of GABAA receptor activity in rat hippocampus.

An interaction with the GABA type A (GABA(A)) receptor has long been recognized as one of the main neurochemical mechanisms underlying many of the pharmacological actions of ethanol. However, more recent data have suggested that certain behavioral and electrophysiological actions of ethanol are mediated by an increase in brain concentration of neuroactive steroids that results from stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. Neuroactive steroids such as 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) are, in fact, potent and efficacious endogenous positive modulators of GABA(A) receptor function. Because neurosteroids can be synthesized de novo in the brain, we have investigated whether ethanol might affect both neurosteroid synthesis and GABA(A) receptor function in isolated rat hippocampal tissue. Here, we show that ethanol increases the concentration of 3alpha,5alpha-THP as well as the amplitude of GABA(A) receptor-mediated IPSCs recorded from CA1 pyramidal neurons in isolated hippocampal slices. These effects are shared by the neurosteroid precursor progesterone, the peripheral benzodiazepine receptor-selective agonist CB34, and gamma-hydroxybutyrate, all of which are known to increase the formation of neuroactive steroids in plasma and in the brain. The action of ethanol on GABA(A) receptor-mediated IPSC amplitude is biphasic, consisting of a rapid, direct effect on GABA(A) receptor activity and an indirect effect that appears to be mediated by neurosteroid synthesis. Furthermore, ethanol affects GABA(A) receptor activity through a presynaptic action, an effect that is not dependent on neurosteroid formation. These observations suggest that ethanol may modulate GABA(A) receptor function through an increase in de novo neurosteroid synthesis in the brain that is independent of the HPA axis. This novel mechanism may have a crucial role in mediating specific central effects of ethanol.

Ethanol-induced increases in neuroactive steroids in the rat brain and plasma are absent in adrenalectomized and gonadectomized rats

Peripheral administration of alcohol has been demonstrated to cause significant increases in neurosteroid levels in the brain and periphery. These findings have led to several theories suggesting a role for neurosteroids in the actions of alcohol. However, the anatomical sources of these steroids (e.g., brain or periphery) are as yet unknown. This study utilized gas chromatography/mass spectrometry (GC/MS) to assess the levels of several neuroactive steroids in plasma and brain frontal cortex 30–360 min following acute administration of alcohol (2 g/kg, i.p.). Concentrations of pregnenolone, allopregnanolone (3α-hydroxy-5α-pregnan-20-one), and allotetrahydrodeoxycorticosterone (3α,21-dihydroxy-5α-pregnan-20-one) were all measured. In order to determine the contribution of peripheral endocrine organs to neurosteroid responses, neuroactive steroid levels were measured in both intact and adrenalectomized/gonadectomized male Wistar rats 30 min after acute administration of alcohol. Intact animals exhibited a maximal increase of pregnenolone in plasma and frontal cortex 30 min after acute administration of alcohol. In addition, allopregnanolone levels increased, with a maximal effect observed at 60 min in plasma. However, in the adrenalectomized/gonadectomized groups treated with alcohol, no significant increases of pregnenolone, allopregnanolone, or allotetrahydrodeoxycorticosterone were found after 30 min. Thus, the alcohol-induced response was associated first with a relatively rapid increase in the first and rate-limiting step in the conversion of cholesterol to steroids, leading to increases in pregnenolone levels. This response was followed by the further secretion of the anxiolytic neuroactive steroids allopregnanolone and allotetrahydrodeoxycorticosterone, both of which appeared to be of adrenal and gonadal origin.

Ethanol rapidly induces steroidogenic acute regulatory protein expression and translocation in rat adrenal gland

Acute ethanol exposure increases GABAergic neuroactive steroids in plasma and brain by releasing these steroids or their precursors from the adrenal glands. The present study showed that ethanol administration rapidly increases the expression of steroidogenic acute regulatory protein (StAR) in the cytosolic and mitochondrial fractions of adrenal glands. The increased StAR protein expression paralleled increases in plasma pregnenolone, progesterone and corticosterone levels. The rapid synthesis and translocation of StAR protein in adrenals likely represent the mechanism of ethanol-induced increases in neuroactive steroids.

Novel 2-phenylimidazo[1,2-a]pyridine derivatives as potent and selective ligands for peripheral benzodiazepine receptors: synthesis, binding affinity, and in vivo studies.

The substituent effects at positions 6 and 8 (compounds 17-31) as well as at the amide nitrogen (compounds 32-40) of a series of 2-phenylimidazo[1,2-a]pyridineacetamides were evaluated at both central (CBR) and peripheral (PBR) benzodiazepine receptors. The structure-activity relationship studies detailed herein indicate the key structural features required for high affinity and selectivity for PBR. Substitution on the imidazopyridine nucleus at position 8 with lipophilic substituents and the presence of one chlorine atom at the para position of the phenyl ring at C(2) are crucial features for high binding affinity and selectivity toward PBR. A small subset of active ligands (i.e., 17, 20, 26, 34, and 35) were evaluated in vitro in Xenopus oocytes expressing cloned human GABA(A) receptors for their effects at CBR and in vivo for their ability to stimulate the synthesis of neurosteroids such as pregnenolone, progesterone, allopregnanolone, and allotetrahydrodeoxycorticosterone (THDOC). Compounds 17, 20, 26, and 34 markedly increased the levels of neuroactive steroids in plasma and cerebral cortex, unlike compound 35.

2-Phenyl-imidazo[1,2-a]pyridine derivatives as ligands for peripheral benzodiazepine receptors: stimulation of neurosteroid synthesis and anticonflict action in rats.

Selective activation of peripheral benzodiazepine receptors (PBRs) in adrenal cells and brain oligodendrocytes promotes steroidogenesis. Three 2-phenyl-imidazo[1,2-a]pyridine derivatives (CB 34, CB 50 and CB 54) have now been investigated with regard to their selectivity for PBRs and their ability to stimulate central and peripheral steroidogenesis in rats. The three CB compounds (10(-10)-10(-4) M) potently inhibited the binding of the PBR ligand [3H]-PK 11195 to brain and ovary membranes in vitro, without substantially affecting [3H]-flunitrazepam binding to central benzodiazepine receptors. These compounds (10(-7)-10(-4) M) also had little or no marked effects on GABA-evoked Cl- currents in voltage-clamped Xenopus oocytes expressing human alpha1beta2gamma2S GABA(A) receptors. In addition, they failed to affect ligands binding to GABA(B), D1/D2 dopamine, muscarinic acetylcholine, N-methyl-D-aspartic acid and opiate receptors. Intraperitoneal administration of CB compounds (3-50 mg kg(-1)) induced a dose-dependent increase in the concentrations of neuroactive steroids in plasma and brain. The brain concentrations of pregnenolone, progesterone, allopregnanolone and allotetrahydrodeoxycorticosterone (THDOC) showed maximal increases in 96+/-3, 126+/-14, 110+/-12 and 70+/-13% above control, respectively, 30 to 60 min after injection of CB 34 (25 mg kg(-1)). CB 34 also increased the brain concentrations of neuroactive steroids in adrenalectomized-orchiectomized rats, although to a lesser extent than in sham-operated animals, suggesting that CB compounds stimulate brain steroidogenesis independently of their effects on peripheral tissues. The increase in brain and plasma neurosteroid content induced by CB 34 was associated with a marked anticonflict effect in the Vogel test. Our results indicate that the three CB compounds tested are specific and potent agonists at peripheral benzodiazepine receptors, and that they stimulate steroidogenesis in both the brain and periphery.

Marked decrease of plasma neuroactive steroids during alcohol withdrawal.

The neuroactive steroids allopregnanolone (ALLO) and allotet-rahydrodeoxycorticosterone (THDOC) are the most potent endogens positive modulators of gamma-aminobutyric acid (GABA) on GABAA receptors, a receptor system presumably responsible for some behavioral responses to alcohol withdrawal. In a group of nine alcoholic subjects, the levels of plasma ALLO and THDOC were markedly lower than those of control subjects during the early withdrawal phase (day 4 and 5), when anxiety and depression scores were higher. In contrast ALLO and THDOC plasma levels did not differ from those of control subjects during the late withdrawal phase when anxiety and depression scores were low. These results suggest that the decrease of neuroactive steroid biosynthesis may contribute to the withdrawal symptoms.

Isoniazid-induced Inhibition of GABAergic Transmission Enhances Neurosteroid Content in the Rat Brain

Isoniazid (375 mg/kg, s.c.), a drug that decreases GABAA receptor-mediated transmission, elicited a time-dependent increase of neuroactive steroid (pregnenolone, progesterone and allotetrahydrodeoxycorticosterone) concentrations in rat brain and plasma. This treatment also time-dependently increased the plasma concentration of corticosterone. Brain and plasma neuroactive steroid levels peaked between 40 and 120 min after isoniazid administration, respectively, and returned to control values by 5 hr. Acute foot shock stress mimicked the effect of isoniazid by increasing in a time-dependent manner the same neuroactive steroids both in brain and plasma. Abecarnil (0.3 mg/kg, i.p.), a β-carboline derivative with anxiolytic properties, antagonized the effect of both isoniazid and foot shock on brain and plasma neuroactive steroids and on plasma corticosterone level. These data indicate that an inhibition of central GABAergic transmission enhances the concentrations of THDOC and its precursors pregnenolone and progesterone in the rat brain and plasma as well as the plasma levels of corticosterone. This finding suggests that GABA exerts a tonic inhibitory action on the mechanisms involved in the regulation of the synthesis and release of these neuroactive steroids in the central nervous system and plasma. Copyright © 1996 Elsevier Science Ltd.