Role of neuroactive steroid allopregnanolone in antipsychotic-like action of olanzapine in rodents

Conversion of 5α-Androstane-3α,17β-diol to bis[(4-dimethylamino)phenyl carbamate] derivative for sensitive determination of its rat brain level by LC/ESI-MS/MS

RATIONALE

5α-Androstane-3α,17β-diol (3α,5α-Adiol) is a testosterone-derived neurosteroid and has anxiolytic and analgesic effects via γ-aminobutyric acid type A receptors as with the progesterone-derived neurosteroid, allopregnanolone (AP). Although the psychotropic drug-evoked changes in the brain AP concentration have been intensively studied, those in the brain 3α,5α-Adiol concentration remain poorly understood. One of the causes for this is the limited availability of a validated method for quantifying the brain 3α,5α-Adiol with a sufficient sensitivity and specificity, which is described in this study.

METHODS

To enhance the detectability of 3α,5α-Adiol by electrospray ionization-tandem mass spectrometry (ESI-MS/MS), derivatization with 4-dimethylaminobenzoyl azide was employed. The brain sample was purified by solid-phase extraction and the recovered 3α,5α-Adiol and the deuterated internal standard were derivatized, then measured by liquid chromatography (LC)/ESI-MS/MS with selected reaction monitoring.

RESULTS

The derivatized 3α,5α-Adiol, i.e., the bis[(4-dimethylamino)phenyl carbamate] derivative, provided the intense doubly-protonated molecule as the precursor ion, then the specific product ion containing the 3α,5α-Adiol-skeleton by collision-induced dissociation. The detectability of 3α,5α-Adiol was eventually increased 1000-fold by derivatization. Separation of the derivatized 3α,5α-Adiol from its stereoisomers and interfering brain components was achieved using a SunShell Biphenyl column with an isopropyl alcohol-containing mobile phase. A good linearity in the sufficient concentration range, acceptable precision and accuracy, and negligible matrix effect were demonstrated by the validation tests. The animal (rat) study using this method revealed that the brain 3α,5α-Adiol levels were unaffected by the administration of fluoxetine (FLX) and clozapine (CLZ), in contrast to the significant increase of the AP levels.

CONCLUSION

An LC/ESI-MS/MS method capable of quantifying 3α,5α-Adiol in the rat brain using a 20-mg tissue was developed and validated. The brain levels of 3α,5α-Adiol had an entirely different behavior from those of AP due to FLX and CLZ administration.

Sex steroid hormones in depressive disorders as a basis for new potential treatment strategies

The sex steroid hormones (SSHs) such as testosterone, estradiol, progesterone, and their metabolites have important organizational and activational impacts on the brain during critical periods of brain development and in adulthood. A variety of slow and rapid mechanisms mediate both organizational and activational processes via intracellular or membrane receptors for SSHs. Physiological concentrations and distribution of SSHs in the brain result in normal brain development. Nevertheless, dysregulation of hormonal equilibrium may result in several mood disorders, including depressive disorders, later in adolescence or adulthood. Gender differences in cognitive abilities, emotions as well as the 2-3 times higher prevalence of depressive disorders in females, were already described. This implies that SSHs may play a role in the development of depressive disorders. In this review, we discuss preclinical and clinical studies linked to SSHs and development of depressive disorders. Our secondary aim includes a review of up-to-date knowledge about molecular mechanisms in the pathogenesis of depressive disorders. Understanding these molecular mechanisms might lead to significant treatment adjustments for patients with depressive disorders and to an amelioration of clinical outcomes for these patients. Nevertheless, the impact of SSHs on the brain in the context of the development of depressive disorders, progression, and treatment responsiveness is complex in nature, and depends upon several factors in concert such as gender, age, comorbidities, and general health conditions.

Metabolic, genetic, and pharmacokinetic parameters for the prediction of olanzapine efficacy

Clinical use of the a olanzapine has significantly different individual-to-individual outcomes. Accordingly, this study aimed to develop a means of predicting response to olanzapine using a combined approach based on pharmacokinetics, pharmacometabonomics, and genetic polymorphism. The olanzapine pharmacokinetics of 19 healthy volunteers treated with orally disintegrating tablets were determined using high-performance liquid chromatography-tandem mass spectrometry. Metabolic profiling and phenotyping were performed on the blood samples that remained after pharmacokinetic analysis using ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry. Uridine diphosphate-glucuronosyltransferase (UGT), tyrosine hydroxylase (TH), γ-aminobutyric acid transaminase (GABA-T), and succinic semialdehyde dehydrogenase (SSADH) were identified as key genes. The single nucleotide polymorphism genotypes most related to drug metabolism were investigated by polymerase chain reaction and Sanger sequencing. Forty-one metabolites (p < 0.05) are increased or decreased after treatment with olanzapine. Tryptophan metabolism, norepinephrine metabolism, and γ-aminobutyric acid metabolism were identified as being related to the effects of olanzapine. Subjects carrying rs1641031 AC and CC exhibited a 59.2% increase in the mean peak concentration (C_max) value and a 25.33% decrease in the mean oral clearance rate (CL/F) value, compared to that in subjects with the GABA-T rs1641031 AA genotype (p < 0.05). Moreover, polymorphism of the GABA-T gene has an impact on the metabolism of 5-hydroxytryptamine. Lysophosphatidylethanolamine (0:0/18:3), lysophosphatidylethanolamine (0:0/22:5), and octadecatrienoic acid distinguish subjects with high and low olanzapine drug oral clearance and are thus identified as biomarkers for predicting its efficacy.

Effect of Co-Treatment of Olanzapine with SEP-363856 in Mice Models of Schizophrenia

Olanzapine is a commonly used drug in the treatment of schizophrenia, but its clinical application has been restricted by metabolic-related side effects. In order to mitigate the weight gain side effects caused by olanzapine, other drugs with different targets were selected for combined use and evaluated in animal models of schizophrenia. SEP-363856 is a novel psychotropic agent which is under phase III clinical trials for schizophrenia treatment. The aim of the research was to evaluate whether co-administration of olanzapine and SEP-363856 exerts synergistic anti-schizophrenic effects in the apomorphine (APO)-induced climbing test, the MK-801-induced hyperactivity test, and the Morris water maze test, and therefore reduces the weight gain side effects induced by olanzapine. Through isobolographic analysis, the results showed a synergistic interaction in the climbing test; the experimental ED30 (3 mg/kg) was significantly smaller (p < 0.05) than the theoretical ED30 (5 mg/kg). Additionally, such potentiating effects appeared additive in the MK-801 challenge experiment. Co-treatment with an effective dose of olanzapine and a low dose of SEP-363856 reversed MK-801-induced cognitive impairment symptoms in mice. Moreover, combination treatment with olanzapine and SEP-363856 controls sustained weight gain in mice with chronic exposure to olanzapine. These results support further clinical trials to test the effectiveness of co-treatment of olanzapine and SEP-363856 for controlling symptoms and weight gain in patients with schizophrenia during antipsychotic treatments.

Antipsychotics increase steroidogenic enzyme gene expression in the rat brainstem

Background

Neurosteroids are involved in several important brain functions and have recently been considered novel players in the mechanic actions of neuropsychiatric drugs. There are no reports of murine studies focusing on the effect of chronic neurosteroid treatment in parallel with antipsychotics on key steroidogenic enzyme expression and we therefore focused on steroidogenic enzyme gene expression in the brainstem of rats chronically treated with olanzapine and haloperidol.

Methods and results

Studies were carried out on adult, male Sprague–Dawley rats which were divided into 3 groups: control and experimental animals treated with olanzapine or haloperidol. Total mRNA was isolated from homogenized brainstem samples for RealTime-PCR to estimate gene expression of related aromatase, 3β-HSD and P450scc. Long-term treatment with the selected antipsychotics was reflected in the modulation of steroidogenic enzyme gene expression in the examined brainstem region; with both olanzapine and haloperidol increasing aromatase, 3β-HSD and P450scc gene expression.

Conclusions

The present findings shed new light on the pharmacology of antipsychotics and suggest the existence of possible regulatory interplay between neuroleptic action and steroidogenesis at the level of brainstem neuronal centres.

Antipsychotic-like profile of CIQ isomers in animal models of schizophrenia

Earlier, we have shown the efficacy of racemic (±) CIQ, a positive allosteric modulator of GluN2C/2D receptor against MK-801 induced impairment of prepulse inhibition as well as working memory. The present study investigated the antipsychotic-like profile of different CIQ (±, +, -) isomers against schizophrenia-like symptoms in series of behavioural animal models like apomorphine climbing, social isolation behaviour and NMDA receptor antagonist MK-801 induced cognitive deficits. Further, we also tested CIQ (±, +, -) isomers in neurodevelopmental model against MK-801induced deficits using open field test, Y-maze test and novel object recognition test. CIQ (±, +, -) isomers decreased climbing behaviour, increased social interaction and improved the MK-801 induced deficits in working memory in Y-maze. Further, CIQ (±, +) but not CIQ (-) improved the recognition memory in novel object recognition test as well as reduced hyperlocomotion and stereotyped behaviour. We conclude that CIQ (±, +) but not CIQ (-) exhibit the significant antipsychotic-like profile.

Allopregnanolone in mood disorders: Mechanism and therapeutic development

The neuroactive steroid allopregnanolone (ALLO) is an endogenous positive allosteric modulator of GABA type A receptor (GABA_AR), and the down-regulation of its biosynthesis have been attributed to the development of mood disorders, such as depression, anxiety and post-traumatic stress disorder (PTSD). ALLO mediated depression/anxiety involves GABAergic mechanisms and appears to be related to brain-derived neurotrophic factor (BDNF), dopamine receptor, glutamate neurotransmission, and Ca²⁺ channel. In the clinical, brexanolone, as a newly developed intravenous ALLO preparation, has been approved for the treatment of postpartum depression (PPD). In addition, traditional antidepressants such as selective serotonin reuptake inhibitor (SSRI) could reverse ALLO decline. Recently, the translocation protein (TSPO, 18 kDa), which involves in the speed-limiting step of ALLO synthesis, and ALLO derivatization have been identified as new directions for antidepressant therapy. This review provides an overview of ALLO researches in animal model and patients, discusses its role in the development and treatment of depression/anxiety, and directs its therapeutic potential in future.

Stress and drug abuse-related disorders: The promising therapeutic value of neurosteroids focus on pregnenolone-progesterone-allopregnanolone pathway

The pregnenolone-progesterone-allopregnanolone pathway is receiving increasing attention in research on the role of neurosteroids in pathophysiology, particularly in stress-related and drug use disorders. These disorders involve an allostatic change that may result from deficiencies in allostasis or adaptive responses, and may be downregulated by adjustments in neurotransmission by neurosteroids. The following is an overview of findings that assess how pregnenolone and/or allopregnanolone concentrations are altered in animal models of stress and after consumption of alcohol or cannabis-type drugs, as well as in patients with depression, anxiety, post-traumatic stress disorder or psychosis and/or in those diagnosed with alcohol or cannabis use disorders. Preclinical and clinical evidence shows that pregnenolone and allopregnanolone, operating according to a different or common pharmacological profile involving GABAergic and/or endocannabinoid system, may be relevant biomarkers of psychiatric disorders for therapeutic purposes. Hence, ongoing clinical trials implicate synthetic analogs of pregnenolone or allopregnanolone, and also modulators of neurosteroidogenesis.

Enhanced remyelination during late pregnancy: involvement of the GABAergic system

Pregnant women with MS experience fewer relapses, especially during the third trimester. In this study, we explore the cellular and molecular events that bring about the protective effect of late pregnancy on the course of de/remyelination in rats. Using cellular, molecular, and ultrastructural methods, we explored remyelination in response to a focal demyelination in the corpus callosum of late pregnant, virgin, and postpartum rats. We further explored the role of GABA_A receptor (GABA_AR) in the promyelinating effect observed during late pregnancy. Remyelination in response to a gliotoxin-induced demyelination in the corpus callosum was enhanced in late pregnant rats when compared to that seen in virgin and postpartum rats. This pregnancy-associated promyelinating effect was lost when either the GABA_AR was blocked or when 5α-reductase, the rate limiting enzyme for the endogenous GABA_AR activator allopregnanolone, was inhibited. Taken together, these data suggest that the pregnancy-associated pro-myelination operates, at least in part, through a GABAergic activated system.

A Case of Schizophrenia With Catatonia Resistant to Lorazepam and Olanzapine Monotherapy But Responsive to Combination Treatment: Is It Time to Consider Using Select Second-Generation Antipsychotics Earlier in the Treatment Algorithm for This Patient Type?

OBJECTIVE

Catatonia is a distinct psychomotor syndrome that involves a constellation of up to 40 different symptoms. Although conventionally responsive to benzodiazepines, the catatonic syndrome is much more resistant to benzodiazepine treatment when a feature of schizophrenia.

METHOD

We present a patient with schizophrenia with catatonic symptoms, marginally responsive to lorazepam challenge, lorazepam, and olanzapine monotherapy, but ultimately began combination treatment with these 2 medications.

RESULTS

Our patient's score on the Bush-Francis Catatonia Rating Scale significantly decreased after 2 weeks of combination lorazepam and olanzapine without adverse effects.

CONCLUSION

We propose a modification to the standard treatment protocol for catatonia, especially in those patients with schizophrenia with catatonic features.

Neurosteroid Actions in Memory and Neurologic/Neuropsychiatric Disorders

Memory dysfunction is a symptomatic feature of many neurologic and neuropsychiatric disorders; however, the basic underlying mechanisms of memory and altered states of circuitry function associated with disorders of memory remain a vast unexplored territory. The initial discovery of endogenous neurosteroids triggered a quest to elucidate their role as neuromodulators in normal and diseased brain function. In this review, based on the perspective of our own research, the advances leading to the discovery of positive and negative neurosteroid allosteric modulators of GABA type-A (GABA_A), NMDA, and non-NMDA type glutamate receptors are brought together in a historical and conceptual framework. We extend the analysis toward a state-of-the art view of how neurosteroid modulation of neural circuitry function may affect memory and memory deficits. By aggregating the results from multiple laboratories using both animal models for disease and human clinical research on neuropsychiatric and age-related neurodegenerative disorders, elements of a circuitry level view begins to emerge. Lastly, the effects of both endogenously active and exogenously administered neurosteroids on neural networks across the life span of women and men point to a possible underlying pharmacological connectome by which these neuromodulators might act to modulate memory across diverse altered states of mind.

Neuroactive Steroids and Cognitive Functions in First-Episode Psychosis Patients and Their Healthy Siblings

Background: Neuroactive steroids (NAS) affect neurotransmitter systems and cognition; thus, they play role in etiopathogenesis of psychiatric disorders. Aims: The primary aim was to examine cognition and effects of NAS on cognitive functioning in first-episode psychosis patients and in their healthy siblings. The secondary aims were to verify whether cognitive deficit is an endophenotype of psychosis and whether higher NAS levels represent a high-risk factor for psychosis. Methods: Studied participants were 1) patients with first episode of psychosis, 2) healthy siblings of the patients, and 3) matching healthy controls. Study procedures included administration of a battery of neuropsychological tests assessing six cognitive domains and examination of NAS plasma levels [cortisol (CORT), 11-deoxycorticosterone (DOC), testosterone (TEST), dehydroepiandrostendione (DHEA), dihydrotestosterone (DHT), and progesterone (PROG)]. Results: A total of 67 subjects were analyzed (16 patients, 22 siblings, and 29 controls). Significant group differences were found in most of the cognitive domains; the patients had the lowest scores. The Kruskal-Wallis test revealed significant group differences in CORT levels (p < 0.01), TEST (p < 0.01), and DHT (p < 0.001); no difference was found in PROG, DHEA, and DOC. All cognitive domains, except for attention, were affected by the NAS levels. CORT levels of patients correlated with speed of processing (r = 0.55) and working memory (r = 0.52), while PROG levels correlated with abstraction (r = -0.63). In siblings, there was a negative correlation between TEST levels and verbal memory (r = -0.51) and PROG with attention (r = -0.47). Conclusions: Our results verified that individual domains of cognitive deficit (abstraction and verbal memory) can be considered as an endophenotype of psychosis. Higher levels of cortisol and testosterone in siblings are consistent with high-risk states for psychosis. Multiple interactions between NAS and cognitive functioning, particularly memory functions, were observed. Study limitations (small sample size and administration of antipsychotic medication) did not allow us to establish unequivocally NAS as an endophenotype.

A role of neuropeptide CART in hyperphagia and weight gain induced by olanzapine treatment in rats

Although olanzapine is highly efficacious and most widely used second generation antipsychotic drug, the success of treatment has been hampered by its propensity to induce weight gain. While the underlying neuronal mechanisms are unclear, their elucidation may help to target alternative pathways regulating energy balance. The present study was undertaken to define the role of cocaine- and amphetamine-regulated transcript (CART), a well-known anorexic peptide, in olanzapine-induced hyperphagia and body weight gain in female rats. Olanzapine was administered daily by intraperitoneal route, alone or in combination with CART (intracerebroventricular) for a period of two weeks. Immediately after drug administrations, preweighed food was offered to the animals at the commencement of the dark phase. The food intake and body weight were measured daily just prior to next injection. Furthermore, the brains of olanzapine-treated rats were processed for the immunohistochemical analysis of CART-containing elements in the hypothalamus. Treatment with olanzapine (0.5 mg/kg) for the duration of 14 days produced a significant increase in food intake and body weight as compared to control. However, concomitant administration of CART (0.5 µg) attenuated the olanzapine-induced hyperphagia and weight gain. Olanzapine administration resulted in a significant reduction in CART immunoreactivity in the hypothalamic arcuate, paraventricular, dorsomedial and ventromedial nuclei. We suggest that decreased CART contents in the hypothalamus may be causally linked with the hyperphagia and weight gain induced by olanzapine.

Pregnenolone-progesterone-allopregnanolone pathway as a potential therapeutic target in first-episode antipsychotic-naïve patients with schizophrenia

Neurosteroids are both endogenous and exogenous steroids that rapidly alter neuronal excitability through interactions with ligand-gated ion channels and other cell surface receptors. They are originated from cholesterol and have important implications for schizophrenia (SZ) pathophysiology and treatment strategies. Specifically, pregnenolone (PREG), progesterone (PROG) and allopregnanolone (ALLO) exhibit similar psychotropic properties. Using enzyme immunoassay, we compared the neurosteroids in PREG downstream pathways in plasma between healthy controls (HC, n = 43) and first-episode antipsychotic-naïve patients with SZ (FEAN-SZ, n = 53) before antipsychotic drug (APD) treatment. Comparisons were also made particularly along PREG-PROG-ALLO pathway in the same FEAN-SZ patients across multiple time points following initiation of treatment for 12 months (m). Firstly, at baseline, levels of PREG were significantly higher and those of ALLO were lower in FEAN-SZ than in HC, whereas PROG, cortisol, dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) were not different. Consequently, the molar ratios of ALLO/PREG and ALLO/PROG in FEAN-SZ were significantly reduced. Secondly, in response to APD at 1 month, ALLO levels in FEAN-SZ were markedly elevated, whereas PREG and PROG levels decreased. Thirdly, among FEAN-SZ, lower levels of PROG (reflecting higher conversion to ALLO) at baseline may predict better therapeutic outcome after 1 month of APD treatment. These findings point to the perturbations of the PREG-PROG-ALLO pathway early in psychosis, and further study of this pathway may inform alternative and innovative therapeutic targets for SZ.

Neurosteroids in Schizophrenia: Pathogenic and Therapeutic Implications

Neurosteroids are a group of important endogenous molecules affecting many neural functions in the brain. Increasing evidence suggests a possible role of these neurosteroids in the pathology and symptomatology of schizophrenia (SZ) and other mental disorders. The aim of this review is to summarize the current knowledge about the neural functions of neurosteroids in the brain, and to evaluate the role of the key neurosteroids as candidate modulators in the etiology and therapeutics of SZ. The present paper provides a brief introduction of neurosteroid metabolism and distribution, followed by a discussion of the mechanisms underlying neurosteroid actions in the brain. The content regarding the modulation of the GABAA receptor is elaborated, given the considerable knowledge of its interactions with other neurotransmitter and neuroprotective systems, as well as its ameliorating effects on stress that may play a role in the SZ pathophysiology. In addition, several preclinical and clinical studies suggested a therapeutic benefit of neurosteroids in SZ patients, even though the presence of altered neurosteroid pathways in the circulating blood and/or brain remains debatable. Following treatment of antipsychotic drugs in SZ, therapeutic benefits have also been linked to the regulation of neurosteroid signaling. Specifically, the neurosteroids such as pregnenolone and dehydroepiandrosterone affect a broad spectrum of behavioral functions through their unique molecular characteristics and may represent innovative therapeutic targets for SZ. Future investigations in larger cohorts with long-term follow-ups will be required to ascertain the neuropsychopharmacological role of this yet unexploited class of neurosteroid agents.

Olanzapine: a 5-year perspective

Olanzapine is a novel antipsychotic, approved for the acute and maintenance treatment of schizophrenia and bipolar I disorder. Despite the publicity regarding reported adverse events with the novel antipsychotics, such as weight gain and Type II diabetes mellitus, olanzapine remains a useful and important medicine. It is a selective monoaminergic antagonist with high-affinity binding to a number of receptors thought to be implicated in some psychotic and mood symptoms. The complex pharmacology of olanzapine has lead to studies exploring its use in treating substance abuse, aggression/violence, borderline personality disorder, schizotypal personality disorder, obsessive-compulsive disorder and as a neuroprotective agent in schizophrenia. As the pharmacology of olanzapine and other novel antipsychotics becomes better understood, future effective treatment strategies are likely to match an individual's genetic makeup and receptor profiles to the most compatible agent.

Inhibition of 17α-hydroxylase/C17,20 lyase reduces gating deficits consequent to dopaminergic activation

Cogent evidence points to the involvement of neurosteroids in the regulation of dopamine (DA) neurotransmission and signaling, yet the neurobiological bases of this link remain poorly understood. We previously showed that inhibition of 5α-reductase (5αR), a key neurosteroidogenic enzyme, attenuates the sensorimotor gating deficits induced by DA receptor activation, as measured by the prepulse inhibition (PPI) of the acoustic startle reflex. To extend these findings, the present study was aimed at the assessment of the role of other key neurosteroidogenic enzymes in PPI, such as 17α-hydroxylase/C17,20 lyase (CYP17A1), 3α- and 3β-hydroxysteroid dehydrogenase (HSD), in Sprague-Dawley rats. The PPI deficits induced by the DAergic non-selective agonist apomorphine (APO, 0.25mg/kg, SC) were dose-dependently attenuated by the selective CYP17A1 inhibitor abiraterone (ABI, 10-50mg/kg, IP) in a fashion akin to that of the 5αR inhibitor finasteride (FIN, 100mg/kg, IP). These systemic effects were reproduced by intracerebroventricular injection of ABI (1 μg/1 μl), suggesting the involvement of brain CYP17A1 in PPI regulation. Conversely, the PPI disruption induced by APO was not significantly affected by the 3α- and 3β-HSD inhibitors indomethacin and trilostane. Given that CYP17A1 catalyzes androgen synthesis, we also tested the impact on PPI of the androgen receptor (AR) antagonist flutamide (10mg/kg, IP). However, this agent failed to reverse APO-induced PPI deficits; furthermore, AR endogenous ligands testosterone and dihydrotestosterone failed to disrupt PPI. Collectively, these data highlight CYP17A1 as a novel target for antipsychotic-like action, and suggest that the DAergic regulation of PPI is modulated by androgenic neurosteroids, through AR-unrelated mechanisms.

Antipsychotic-like effect of GLP-1 agonist liraglutide but not DPP-IV inhibitor sitagliptin in mouse model for psychosis

Recent studies indicate a high comorbidity between type-2 diabetes mellitus (T2DM) and neurological disorders. Many are associated with abnormalities in dopamine neurotransmission such as schizophrenia. Because most of the antipsychotic drugs aggravate pre-existing insulin resistance in type-2 diabetics, there is a need to search for alternative antipsychotics. Glucagon like peptide-1 (GLP-1) is a gut hormone primarily involved in glucose homeostasis. GLP-1 agonist (liraglutide) and dipeptidyl peptidase-IV (DPP-IV) inhibitor (sitagliptin) are the US-FDA approved medications for the management of T2DM. However, little is known about their role in dopamine mediated neurological disorders like schizophrenia. To address this, we used apomorphine-induced cage climbing behavior as a murine model for psychosis and examined for potential antipsychotic-like effect of liraglutide and sitagliptin. While acute liraglutide treatment (50 μg/kg; i.p.) significantly attenuated apomorphine (3 mg/kg, s.c.) induced cage climbing, sitagliptin (50mg/kg; i.p.) failed to elicit such effect. This is the first preclinical evidence for antipsychotic-like effect of GLP-1 receptor agonist. These results open an opportunity to explore GLP-1 analogs for their potential to modulate spectrum of dopamine-mediated neurological disorders.

Neurosteroids, stress and depression: potential therapeutic opportunities

Neurosteroids are potent and effective neuromodulators that are synthesized from cholesterol in the brain. These agents and their synthetic derivatives influence the function of multiple signaling pathways including receptors for γ-aminobutyric acid (GABA) and glutamate, the major inhibitory and excitatory neurotransmitters in the central nervous system (CNS). Increasing evidence indicates that dysregulation of neurosteroid production plays a role in the pathophysiology of stress and stress-related psychiatric disorders, including mood and anxiety disorders. In this paper, we review the mechanisms of neurosteroid action in brain with an emphasis on those neurosteroids that potently modulate the function of GABA(A) receptors. We then discuss evidence indicating a role for GABA and neurosteroids in stress and depression, and focus on potential strategies that can be used to manipulate CNS neurosteroid synthesis and function for therapeutic purposes.

Chronic treatment with serotonin reuptake inhibitor antidepressant (SSRI) combined with an antipsychotic regulates GABA-A receptor in rat prefrontal cortex

INTRODUCTION

The combination of selective serotonin reuptake inhibitor (SSRI) antidepressants and antipsychotics is currently used for the treatment of negative symptoms of schizophrenia. However, the biochemical mechanism mediating the clinical effectiveness of this treatment remains obscure. Previously, we have reported that acute haloperidol (HALO)-fluvoxamine (FLU) in vivo and in vitro treatment regulated GABA-Aβ2/3 receptor subunits, and protein kinase C (PKC) and mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) signaling pathways.

FINDINGS

In the present study, we demonstrated that chronic HALO-FLU treatment, but not each drug alone, significantly decreased GABA-Aβ2/3 receptor expression (25 ± 6.2% vs. control) and caused receptor translocation from the membrane to the cytosol in rat prefrontal cortex. Phosphorylation of PKC and ERK2 was affected differently by HALO-FLU combination than by the individual drug treatments. HALO and FLU each given alone increased PKC phosphorylation levels (29 ± 15% and 40 ± 11.8%, vs. control, respectively) and did not affect ERK2 phosphorylation, while HALO-FLU combined treatment did not alter PKC phosphorylation levels and significantly decreased ERK2 phosphorylation levels (58 ± 4.4% vs. control). GABA-A receptor downregulation in the brain was accompanied by a decrease in GABA-A function, as shown in muscimol-induced loss of righting reflex (22 ± 9.8 min).

CONCLUSIONS

We provide a brief heuristic overview of our preclinical and clinical studies with the SSRI-antipsychotic combination and argue that the finding that it causes similar dynamic changes in laboratory and clinical domains, specifically in GABA-A β2/3 receptor and PKC, strongly supports the hypothesis that the GABA-A receptors and their regulatory systems are involved in the molecular mechanisms underlying the clinical effectiveness of SSRI augmentation.

Progesterone turnover to its 5α-reduced metabolites in the ventral tegmental area of the midbrain is essential for initiating social and affective behavior and progesterone metabolism in female rats

BACKGROUND

Among women and female rodents, progesterone (P) influences social affiliation and affect. These effects may be partly due to formation of its 5α-reduced, 3α- hydroxylated metabolite, 5α-pregnan-3α-ol-20-one (3α,5α- THP).

AIM

To elucidate whether actions of 3α,5α-THP in the midbrain ventral tegmental area (VTA) are both necessary and sufficient to enhance non-sexual and sexual social behaviors, affect, and central 3α,5α-THP metabolism.

MATERIALS AND METHODS

P and 3α,5α-THP formation were unperturbed or blocked in VTA via infusions of vehicle, PK11195 (400 ng), and/or indomethacin (10 μg). Rats then received subsequent infusions of vehicle or 3α,5α-THP (100 ng) and were assessed in a battery of tasks that included open field (exploration), elevated plus maze (anxiety behavior), social interaction (social affiliation), and paced mating (sexual behavior) or were not tested. Metabolic turnover of P to its 5α-reduced metabolites was assessed in plasma, midbrain, hippocampus, frontal cortex, diencephalon, and remaining subcortical tissues (control interbrain).

RESULTS

Infusions of any combination of inhibitors significantly reduced social and affective behavior in all tasks compared to vehicle, concomitant with reduced turnover of P to its 5α-reduced metabolites, in midbrain only. Subsequent infusions of 3α,5α-THP significantly reinstated/enhanced anti- anxiety behavior, lordosis, and P turnover to its 5α-reduced metabolites in midbrain, as well as hippocampus, cortex, and diencephalon (but not plasma or interbrain).

CONCLUSIONS

These data are the first to provide direct evidence that actions of 3α,5α-THP in the VTA are both necessary and sufficient for social and affective behavior, as well as initiation of central 5α-reduction.

Midazolam inhibits hippocampal long-term potentiation and learning through dual central and peripheral benzodiazepine receptor activation and neurosteroidogenesis

Benzodiazepines (BDZs) enhance GABA(A) receptor inhibition by direct actions on central BDZ receptors (CBRs). Although some BDZs also bind mitochondrial receptors [translocator protein (18 kDa) (TSPO)] and promote the synthesis of GABA-enhancing neurosteroids, the role of neurosteroids in the clinical effects of BDZs is unknown. In rat hippocampal slices, we compared midazolam, an anesthetic BDZ, with clonazepam, an anticonvulsant/anxiolytic BDZ that activates CBRs selectively. Midazolam, but not clonazepam, increased neurosteroid levels in CA1 pyramidal neurons without changing TSPO immunostaining. Midazolam, but not clonazepam, also augmented a form of spike inhibition after stimulation adjacent to the pyramidal cell layer and inhibited induction of long-term potentiation. These effects were prevented by finasteride, an inhibitor of neurosteroid synthesis, or 17PA [17-phenyl-(3α,5α)-androst-16-en-3-ol], a blocker of neurosteroid effects on GABA(A) receptors. Moreover, the synaptic effects were mimicked by a combination of clonazepam with FGIN (2-[2-(4-fluorophenyl)-1H-indol-3-yl]-N,N-dihexylacetamide), a selective TSPO agonist, or a combination of clonazepam with exogenous allopregnanolone. Consistent with these in vitro results, finasteride abolished the effects of midazolam on contextual fear learning when administrated 1 d before midazolam injection. Thus, dual activation of CBRs and TSPO appears to result in unique actions of clinically important BDZs. Furthermore, endogenous neurosteroids are shown to be important regulators of pyramidal neuron function and synaptic plasticity.

Anxiolytic-like property of risperidone and olanzapine as examined in multiple measures of fear in rats

Atypical antipsychotics are also used in the treatment of anxiety-related disorders. Clinical and preclinical evidence regarding their intrinsic anxiolytic efficacy has been mixed. In this study, we examined the potential anxiolytic-like effects of risperidone and olanzapine, and compared them with haloperidol, chlordiazepoxide (a prototype of sedative-anxiolytic drug) or citalopram (a selective serotonin reuptake inhibitor). We used a composite of two-way avoidance conditioning and acoustic startle reflex model and examined the effects of drug treatments during the acquisition phase (Experiment 1) or extinction phase (Experiments 2 and 3) on multiple measures of conditioned and unconditioned fear/anxiety-like responses. In Experiment 4, we further compared risperidone, olanzapine, haloperidol, citalopram and chlordiazepoxide in a standard elevated plus maze test. Results revealed three distinct anxiolytic-like profiles associated with risperidone, olanzapine and chlordiazepoxide. Risperidone, especially at 1.0mg/kg, significantly decreased the number of avoidance responses, 22kHz ultrasonic vocalization, avoidance conditioning-induced hyperthermia and startle reactivity, but did not affect defecations or time spent on the open arms. Olanzapine (2.0mg/kg, sc) significantly decreased the number of avoidance responses, 22kHz vocalization and amount of defecations, but it did not inhibit startle reactivity and time spent on the open arms. Chlordiazepoxide (10mg/kg, ip) significantly decreased the number of 22kHz vocalization, avoidance conditioning-induced hyperthermia and amount of defecations, and increased time spent on the open arms, but did not decrease avoidance responses or startle reactivity. Haloperidol and citalopram did not display any anxiolytic-like property in these tests. The results highlight the importance of using multiple measures of fear-related responses to delineate behavioral profiles of psychotherapeutic drugs.

Effects of a positive allosteric modulator of mGluR5 ADX47273 on conditioned avoidance response and PCP-induced hyperlocomotion in the rat as models for schizophrenia

Metabotropic glutamate receptors of the subtype 5 (mGluR(5)) are located in brain regions implicated in schizophrenia such as the cerebral cortex or the nucleus accumbens. They may therefore provide an interesting target for the treatment of psychoses. Currently available agonists of mGluR(5) are not selective, do not penetrate the brain and induce a tonic activation resulting in a rapid desensitization. Therefore, the research focus was shifted to positive allosteric modulators (PAMs). Subsequently several mGluR(5) PAMs have been discovered, e.g. ADX47273 (S-(4-fluoro-phenyl)-{3-[3-(4-fluoro-phenyl)-[1,2,4]oxadiazol-5-yl]-piperidin-1-yl}-methanone). In the present study, effects of ADX47273 (1-100mg/kg) were evaluated in rat models used for detecting antipsychotic-like activity: the conditioned avoidance response (CAR) and the phencyclidine (PCP)-induced hyperlocomotion models. Furthermore, the cataleptogenic potential of ADX47273 was compared to that of haloperidol. ADX47273 (100mg/kg) and various clinically used neuroleptics (haloperidol, olanzapine, and aripiprazole) attenuated CAR behaviour in rats. However, ADX47273 and aripiprazole failed to reduce the PCP-induced hyperlocomotion, whereas olanzapine and haloperidol diminished it. In contrast to haloperidol, ADX47273 (100mg/kg) failed to induce consistent catalepsy in rats. In conclusion, ADX47273 shows promising antipsychotic activity in some tests which require future investigation.

GABA(A) receptors and their associated proteins: implications in the etiology and treatment of schizophrenia and related disorders

Gamma-aminobutyric acid type A (GABA(A)) receptors play an important role in mediating fast synaptic inhibition in the brain. They are ubiquitously expressed in the CNS and also represent a major site of action for clinically relevant drugs. Recent technological advances have greatly clarified the molecular and cellular roles played by distinct GABA(A) receptor subunit classes and isoforms in normal brain function. At the same time, postmortem and genetic studies have linked neuropsychiatric disorders including schizophrenia and bipolar disorder with GABAergic neurotransmission and various specific GABA(A) receptor subunits, while evidence implicating GABA(A)R-associated proteins is beginning to emerge. In this review we discuss the mounting genetic, molecular, and cellular evidence pointing toward a role for GABA(A) receptor heterogeneity in both schizophrenia etiology and therapeutic development. Finally, we speculate on the relationship between schizophrenia-related disorders and selected GABA(A) receptor associated proteins, key regulators of GABA(A) receptor trafficking, targeting, clustering, and anchoring that often carry out these functions in a subtype-specific manner.

A possible participation of gonadotropin-releasing hormone in the neuroleptic and cataleptic effect of haloperidol

Haloperidol, an antipsychotic agent, stimulates the release of gonadotropin-releasing hormone (GnRH), and this hormone is known to mimic some of the behavioral effects of haloperidol. Hence, the present study was carried out to find out the contribution of GnRH in the behavioral effects of haloperidol. The studies revealed that haloperidol (0.15, 0.25 and 0.5 mg/kg, i.p.) and leuprolide (GnRH agonist; 50, 100, 200 and 400 microg/kg, s.c.) dose-dependently inhibited conditioned avoidance response (CAR) in male Sprague-Dawley rats. In higher doses, haloperidol (0.5, 1 mg/kg, i.p.) and leuprolide (200, 400 microg/kg, s.c.) produced catalepsy in rats. Co-administration of sub-effective dose of leuprolide (50 or 100 microg/kg, s.c.) and haloperidol (0.15 or 0.5 mg/kg, i.p.) similarly inhibited CAR and induced catalepsy. Pre-treatment of rats with antide (GnRH antagonist; 10 microg/rat, s.c.), attenuated the inhibitory effect of both the agents on CAR; blocked leuprolide-induced catalepsy; and attenuated the intensity and reduced the duration of haloperidol-induced catalepsy. In conclusion, the studies suggest a possible role of GnRH in the neuroleptic and cataleptic effect of haloperidol.

Antipsychotic drugs: comparison in animal models of efficacy, neurotransmitter regulation, and neuroprotection

Various lines of evidence indicate the presence of progressive pathophysiological processes occurring within the brains of patients with schizophrenia. By modulating chemical neurotransmission, antipsychotic drugs may influence a variety of functions regulating neuronal resilience and viability and have the potential for neuroprotection. This article reviews the current literature describing preclinical and clinical studies that evaluate the efficacy of antipsychotic drugs, their mechanism of action and the potential of first- and second-generation antipsychotic drugs to exert effects on cellular processes that may be neuroprotective in schizophrenia. The evidence to date suggests that although all antipsychotic drugs have the ability to reduce psychotic symptoms via D(2) receptor antagonism, some antipsychotics may differ in other pharmacological properties and their capacities to mitigate and possibly reverse cellular processes that may underlie the pathophysiology of schizophrenia.

The biochemical womb of schizophrenia: A review

The conclusive identification of specific etiological factors or pathogenic processes in the illness of schizophrenia has remained elusive despite great technological progress. The convergence of state-of-art scientific studies in molecular genetics, molecular neuropathophysiology, in vivo brain imaging and psychopharmacology, however, indicates that we may be coming much closer to understanding the genesis of schizophrenia. In near future, the diagnosis and assessment of schizophrenia using biochemical markers may become a "dream come true" for the medical community as well as for the general population. An understanding of the biochemistry/ visa vis pathophysiology of schizophrenia is essential to the discovery of preventive measures and therapeutic intervention.

Ethanol intake patterns in female mice: influence of allopregnanolone and the inhibition of its synthesis

The neurosteroid allopregnanolone (ALLO) is a positive modulator of GABA(A) receptors that exhibits a psychopharmacological profile similar to ethanol (i.e., anxiolytic, sedative-hypnotic). Based on research suggesting that manipulation of ALLO levels altered ethanol self-administration in male rodents, the current studies determined whether exogenous ALLO administration or the inhibition of its synthesis in vivo modulated ethanol intake patterns in female C57BL/6J mice. Lickometer circuits collected temporal lick records of ethanol (10%, v/v) and water consumption during daily 2h limited access sessions. Following the establishment of stable ethanol intake, studies examined the effect of an acute ALLO challenge (3.2-24.0 mg/kg) or a 7-day blockade of ALLO production with finasteride (FIN; 50 or 100 mg/kg) on ethanol intake in a within-subjects design. In contrast to results in male mice, ethanol dose (g/kg), ethanol preference and most of the bout parameters were unaltered by ALLO pretreatment in female mice. Ethanol intake in females also was recalcitrant to 7-day treatment with 50 mg/kg FIN, whereas 100 mg/kg FIN significantly reduced the ethanol dose consumed by 35%. The FIN-attenuated ethanol intake was attributable to a significant decrease in bout frequency (up to 45%), with lick patterns indicating reduced maintenance of consumption throughout the 2-h session. FIN also produced a dose-dependent decrease in brain ALLO levels. In conjunction with data in male mice, the present findings indicate that there are sex differences in the physiological regulation of ethanol intake patterns by GABAergic neurosteroids.

Antipsychotic drug administration differentially affects [3H]muscimol and [3H]flunitrazepam GABA(A) receptor binding sites

Post-mortem studies of the human brain indicate that certain GABA(A) receptor subtypes may be differentially altered in schizophrenia. Increased binding to the total population of GABA(A) receptors using [3H]muscimol is observed in the post-mortem schizophrenic brain, yet a proportion of these receptors which bind benzodiazepines and are labelled with [3H]flunitrazepam, show decreased or unaltered expression. Data from animal studies suggest that antipsychotic drugs alter GABA(A) receptor expression in a subtype selective manner, but in the opposite direction to that observed in schizophrenia. To broaden our understanding of the effects of antipsychotic drugs on GABA(A) receptors, we examined the saturation binding maximum (B(max)) and binding affinity (K(D)) of [3H]muscimol and [3H]flunitrazepam in the prefrontal cortex (PFC), hippocampus and thalamus of male SD rats that received a sucrose solution containing either haloperidol (1.5 mg/kg), olanzapine (6.5 mg/kg) or no drug daily for up to 28 days using quantitative receptor autoradiography. [3H]Muscimol binding density was increased most prominently in the PFC after 7 days, with larger and more prolonged effects being induced by the atypical antipsychotic drug olanzapine in subcortical regions. While no changes were observed in [3H]muscimol binding in any region after 28 days of drug administration, [3H]flunitrazepam binding density (B(max)) was increased for both antipsychotic treatments in the PFC only. These findings confirm that the subset of GABA(A) receptors sensitive to benzodiazepines are regulated differently from other GABA(A) receptor subtypes following antipsychotic drug administration, in a time- and region-dependent manner.

The relevance of neuroactive steroids in schizophrenia, depression, and anxiety disorders

1. Neuroactive steroids are steroid hormones that exert rapid, nongenomic effects at ligand-gated ion channels. There is increasing awareness of the possible role of these steroids in the pathology and manifestation of symptoms of psychiatric disorders. The aim of this paper is to review the current knowledge of neuroactive steroid functioning in the central nervous system, and to assess the role of neuroactive steroids in the pathophysiology and treatment of symptoms of schizophrenia, depression, and anxiety disorders. Particular emphasis will be placed on GABAA receptor modulation, given the extensive knowledge of the interactions between this receptor complex, neuroactive steroids, and psychiatric illness. 2. A brief description of neuroactive steroid metabolism is followed by a discussion of the interactions of neuroactive steroids with acute and chronic stress and the HPA axis. Preclinical and clinical studies related to psychiatric disorders that have been conducted on neuroactive steroids are also described. 3. Plasma concentrations of some neuroactive steroids are altered in individuals suffering from schizophrenia, depression, or anxiety disorders compared to values in healthy controls. Some drugs used to treat these disorders have been reported to alter plasma and brain concentrations in clinical and preclinical studies, respectively. 4. Further research is warranted into the role of neuroactive steroids in the pathophysiology of psychiatric illnesses and the possible role of these steroids in the successful treatment of these disorders.

The influence of clozapine treatment and other antipsychotics on the 18 kDa translocator protein, formerly named the peripheral-type benzodiazepine receptor, and steroid production

It has been shown that the atypical antipsychotic drug clozapine increases the levels of the neurosteroid allopregnanolone in the rat brain. The 18 kDa translocator protein (TSPO), formerly known as the peripheral-type benzodiazepine receptor, has been demonstrated to be involved in the process of steroid biosynthesis, in peripheral steroidogenic tissues as well as in glia cells in the brain. In the current study, we investigated the influence of chronic treatment with clozapine and other antipsychotics (thioridazine,sulpiride and risperidone) on TSPO binding in cell cultures and rat tissues. Clozapine significantly increased TSPO binding density in C6 rat glioma cells and in MA-10 mouse Leydig tumor cells, while the antipsychotic sulpiride had no effect on TSPO binding density in both cell lines. In addition, clozapine, but not sulpiride, significantly increased progesterone synthesis by MA-10 Leydig tumor cells. In an animal experiment, male Sprague-Dawley rats were treated with clozapine (20 mg/kg), risperidone (0.5 mg/kg), thioridazine (20 mg/kg), or sulpiride (20 mg/kg) for 21 days, followed by 7 days of withdrawal. Clozapine induced significant increases in TSPO binding in brain and peripheral steroidogenic tissues, whereas the other antipsychotics did not show such pronounced effects on TSPO binding. Our results suggest that TSPO may be involved in the modulation of steroidogenesis by clozapine.

Neurosteroid allopregnanolone mediates anxiolytic effect of etifoxine in rats

Etifoxine (6-chloro-2-ethylamino-4-methyl-4-phenyl-4H-3,1-benzoxazine hydrochloride), a nonbenzodiazepine anxiolytic drug, potentiates GABA(A) receptor function perhaps through stimulation of neurosteroid biosynthesis. However, the exact mechanism of etifoxine action is not fully understood. In this study, we have assessed the possible role of GABAergic neurosteroid like allopregnanolone (ALLO) in the anxiolytic-like effect of etifoxine in rats using elevated plus maze test. Selective GABA(A) receptor agonist, muscimol, ALLO or neurosteroidogenic agents like progesterone, metyrapone or mitochondrial diazepam binding inhibitor receptor (MDR) agonist, FGIN 1-27 significantly heightened the etifoxine-induced anxiolysis. On the other hand, GABA(A) receptor antagonist, bicuculline or neurosteroid biosynthesis inhibitors like finasteride, indomethacin, trilostane or PBR antagonist, PK11195 significantly blocked the effect of etifoxine. Bilateral adrenalectomy did not influence anti-anxiety effect of etifoxine thereby ruling out contribution of adrenal steroids. Thus, our results provide behavioral evidence for the role of neurosteroids like ALLO in the anti-anxiety effect of etifoxine.

Olanzapine and fluoxetine administration and coadministration increase rat hippocampal pregnenolone, allopregnanolone and peripheral deoxycorticosterone: implications for therapeutic actions

Olanzapine and fluoxetine elevate the GABAergic neuroactive steroid allopregnanolone to physiologically relevant concentrations in rodent cerebral cortex. It is unknown if these agents also alter pregnenolone or deoxycorticosterone. Since olanzapine and fluoxetine in combination have clinical utility and may demonstrate synergistic effects, we investigated neuroactive steroid alterations following olanzapine, fluoxetine or coadministration. Male rats received IP vehicle, olanzapine, fluoxetine or the combination of both agents in higher-dose (0, 10, 20 or 10/20 mg/kg, respectively) and lower-dose (0, 5, 10 or 5/10 mg/kg, respectively) experiments. Pregnenolone and allopregnanolone levels in hippocampus were determined by gas chromatography/mass spectrometry. Peripheral deoxycorticosterone and other steroid levels were determined by radioimmunoassay. Olanzapine, fluoxetine or the combination increased hippocampal pregnenolone and serum deoxycorticosterone in both higher- and lower-dose experiments, and elevated hippocampal allopregnanolone in higher-dose conditions. No synergistic effects on pregnenolone or allopregnanolone were observed following olanzapine and fluoxetine coadministration compared to either compound alone. Pregnenolone and its sulfate enhance learning and memory in rodent models, and therefore pregnenolone elevations may be relevant to cognitive changes in psychotic and affective disorders. Since pregnenolone decreases have been linked to depression, it is possible that olanzapine- and fluoxetine-induced pregnenolone elevations may contribute to the antidepressant actions of these agents.

Neuroactive steroids are altered in schizophrenia and bipolar disorder: relevance to pathophysiology and therapeutics

Evidence suggests that neuroactive steroids may be candidate modulators of schizophrenia pathophysiology and therapeutics. We therefore investigated neuroactive steroid levels in post-mortem brain tissue from subjects with schizophrenia, bipolar disorder, nonpsychotic depression, and control subjects to determine if neuroactive steroids are altered in these disorders. Posterior cingulate and parietal cortex tissue from the Stanley Foundation Neuropathology Consortium collection was analyzed for neuroactive steroids by negative ion chemical ionization gas chromatography/mass spectrometry preceded by high-performance liquid chromatography. Subjects with schizophrenia, bipolar disorder, nonpsychotic depression, and control subjects were group matched for age, sex, ethnicity, brain pH, and post-mortem interval (n = 14-15 per group, 59-60 subjects total). Statistical analyses were performed by ANOVA with post-hoc Dunnett tests on log transformed neuroactive steroid levels. Pregnenolone and allopregnanolone were present in human post-mortem brain tissue at considerably higher concentrations than typically observed in serum or plasma. Pregnenolone and dehydroepiandrosterone levels were higher in subjects with schizophrenia and bipolar disorder compared to control subjects in both posterior cingulate and parietal cortex. Allopregnanolone levels tended to be decreased in parietal cortex in subjects with schizophrenia compared to control subjects. Neuroactive steroids are present in human post-mortem brain tissue at physiologically relevant concentrations and altered in subjects with schizophrenia and bipolar disorder. A number of neuroactive steroids act at inhibitory GABA(A) and excitatory NMDA receptors and demonstrate neuroprotective and neurotrophic effects. Neuroactive steroids may therefore be candidate modulators of the pathophysiology of schizophrenia and bipolar disorder, and relevant to the treatment of these disorders.

Rats bred for high versus low anxiety responses neonatally demonstrate increases in lordosis, pacing behavior, and midbrain 3α,5α-THP levels as adults

Duration and intensity of lordosis is mediated by actions of the progesterone (P) metabolite, 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha,5 alpha-THP) at GABA-sub(A) receptors in the midbrain ventral tegmental area. Because rats selectively bred for infantile vocalizations may differ in endogenous 3 alpha,5 alpha-THP secretion, their sexual behavior, midbrain, and plasma 3 alpha,5 alpha-THP levels as adult rats in behavioral estrus was examined. Rats bred for high rates of infantile vocalizations had shorter latencies and intervals between intromissions and ejaculation, higher lordosis quotients and ratings, more pacing of their sexual contacts, and had higher P and 3 alpha,5 alpha-THP levels in plasma and midbrain than did rats bred for low rats of infantile vocalizations. Thus, levels of 3 alpha,5 alpha-THP in the midbrain are associated with differences in sexual behavior of these rats.

Neuroactive steroids in schizophrenia

Schizophrenia is a psychiatric disorder with a complicated pathophysiology, involving many biochemical abnormalities in the brain. Because neuroactive steroids (NASs) modulate neurotransmitter systems that are implicated in the pathology of schizophrenia, recent research has focused on examining the role that NASs play in the illness. Although research in this area is relatively new, it appears that NASs may potentially be implicated in the pathophysiology of the illness. This paper reviews the current understanding of NASs, the research literature on NASs in schizophrenia and in animal models of the illness (including the effects of antipsychotic medication on NASs) and on the potential antipsychotic role of NASs themselves and, finally, discusses future directions for this area of schizophrenia research.

Evaluation of GABAergic neuroactive steroid 3alpha-hydroxy-5alpha-pregnane-20-one as a neurobiological substrate for the anti-anxiety effect of ethanol in rats

RATIONALE

Acute systemic ethanol administration is known to elevate plasma and cerebral levels of neuroactive steroid 3alpha-hydroxy-5alpha-pregnane-20-one (3alpha, 5alpha-THP; allopregnanolone) to a concentration sufficient to potentiate GABA(A) receptors. We have earlier demonstrated that 3alpha, 5alpha-THP mediates the antidepressant-like effect of ethanol in Porsolt forced swim test.

OBJECTIVE

The aim of the present study is to explain the relationship between endogenous GABAergic neurosteroids and anxiolytic effect of ethanol in Sprague-Dawley rats.

METHOD

The mediation of 3alpha, 5alpha-THP in the anti-anxiety effect of ethanol was assessed by pharmacological interactions of ethanol with various endogenous neurosteroidal modulators and using simulated physiological conditions of altered neurosteroid content in elevated plus maze (EPM) test.

RESULTS

Pretreatment of 3alpha, 5alpha-THP (0.5-2.5 mug/rat, i.c.v.) or neurosteroidogenic agents such as 3alpha, 5alpha-THP precursor progesterone (5 or 10 mg/kg, i.p.), 11-beta hydroxylase inhibitor metyrapone (50 or 100 mg/kg, i.p.) or the GABA(A) receptor agonist muscimol (25 ng/rat, i.c.v.) significantly potentiated the anti-anxiety effect of ethanol (1 g/kg, i.p.). On the other hand, the GABAergic antagonistic neurosteroid dehydroepiandrosterone sulphate (DHEAS) (1 mg/kg, i.p.), the GABA(A) receptor blocker bicuculline (1 mg/kg, i.p.), the 5alpha-reductase inhibitor finasteride (50 x 2 mg/kg, s.c.) or the mitochondrial diazepam binding inhibitory receptor antagonist PK11195 (1 mg/kg, i.p.) reduced ethanol-induced preference of time spent and number of entries into open arms. Anti-anxiety effect of ethanol was abolished in adrenalectomized (ADX) rats as compared to sham-operated control. This ADX-induced blockade was restored by prior systemic injection of progesterone, signifying the contribution of peripheral steroidogenesis in ethanol anxiolysis. Socially isolated animals known to exhibit decreased brain 3alpha, 5alpha-THP and GABA(A) receptor functions displayed reduced sensitivity to the effects of ethanol and 3alpha, 5alpha-THP in EPM test.

CONCLUSIONS

Our results demonstrated the contributory role of neuroactive steroid 3alpha, 5alpha-THP in the anti-anxiety effect of ethanol. It is speculated that ethanol-induced modulation of endogenous GABAergic neurosteroids, especially 3alpha, 5alpha-THP, might be crucial pertinent to the etiology of 'trait' anxiety (tension reduction) and ethanol abuse.