Effects of Progesterone on Preclinical Animal Models of Traumatic Brain Injury: Systematic Review and Meta-analysis.

Since the publication of two phase III clinical trials not supporting the use of progesterone in patients with traumatic brain injury (TBI), several possible explanations have been postulated, including limitations in the analysis of results from preclinical evidence. Therefore, to address this question, a systematic review and meta-analysis was performed to evaluate the effects of progesterone as a neuroprotective agent in preclinical animal models of TBI. A total of 48 studies were included for review: 29 evaluated brain edema, 21 evaluated lesion size, and 0 studies reported the survival rate. In the meta-analysis, it was found that progesterone reduced brain edema (effect size - 1.73 [- 2.02, - 1.44], p < 0.0001) and lesion volume (effect size - 0.40 [- 0.65, - 0.14], p = 0.002). Lack of details in the studies hindered the assessment of risk of bias (through the SYRCLE tool). A funnel plot asymmetry was detected, suggesting a possible publication bias. In conclusion, preclinical studies show that progesterone has an anti-edema effect in animal models of TBI, decreasing lesion volume or increasing remaining tissue. However, more studies are needed using assessing methods with lower risk of histological artifacts.

Treatment approach to a patient with catamenial epilepsy. case report

ABSTRACT Introduction: Catamenial epilepsy refers to the worsening or exacerbation of seizures due to hormonal changes during the menstrual cycle. It is thought to be secondary to the neuroactive properties of endogenous steroid hormones and the natural cyclic variation in their serum levels throughout the menstrual cycle. Case presentation: A 31-year-old female patient from Bogotá (Colombia) was admitted to the emergency department due to an episode of tonic-clonic seizure associated with the menstrual period. Since the onset of the seizures was related to menstruation (every 28 days), it was established that the patient had structural focal epilepsy with catamenial features. Advantages of medical vs. surgical treatment were discussed during a multidisciplinary medical board and it was decided to start pharmacological treatment with progestogens, which resulted in complete remission of the seizures as established during a follow-up visit. Conclusions: Catamenial epilepsy should be considered as a cause of epilepsy refractory to antiepileptic medications. Furthermore, it should be approached from a multidisciplinary perspective and its management should be focused on improving the patients' quality of life.

RESUMEN Introducción. La epilepsia catamenial se define como un empeoramiento o la exacerbación de las crisis epilépticas en relación con el cambio hormonal durante el ciclo menstrual femenino. Se cree que esta se produce por las propiedades neuroactivas de las hormonas esteroides endógenas y la variación cíclica natural en sus niveles séricos a lo largo de dicho ciclo. Presentación del caso. Mujer de 31 años de Bogotá (Colombia), quien fue llevada al servicio de urgencias por un episodio de crisis epiléptica con convulsiones tonicoclónicas asociado al período menstrual. Debido a que la aparición de las crisis epilépticas se asociaba con la menstruación (cada 28 días), se estableció que la paciente presentaba epilepsia focal estructural de características catameniales. En junta médica multidisciplinar se discutieron las ventajas del manejo médico y el manejo quirúrgico, y se decidió instaurar tratamiento farmacológico con progestágenos, el cual, tras seguimiento, evidenció supresión total de las crisis. Conclusiones. La epilepsia catamenial debe considerarse como una causa de epilepsia refractaria al tratamiento antiepiléptico. Además, su abordaje debe ser multidisciplinario y su tratamiento debe ir enfocado a mejorar la calidad de vida de los pacientes.

Glioblastoma cells express crucial enzymes involved in androgen synthesis: 3ß-hydroxysteroid dehydrogenase, 17-20α-hydroxylase, 17ß-hydroxysteroid dehydrogenase and 5α-reductase.

Glioblastoma (GB) is the most common and aggressive primary brain tumour in adult humans. Therapeutic resistance and tumour recurrence after surgical removal contribute to poor prognosis for glioblastoma patients. Men are known to be more likely than women to develop an aggressive form of GB, and differences in sex steroids have emerged as a leading explanation for this finding. Studies indicate that the metabolism and proliferation of GB-derived cells are increased by sex steroids, the expression of androgen receptors (ARs) and the synthesis of androgens and oestrogens, suggesting that these hormones have a role in the tumour pathogenesis. The expression of aromatase, the enzyme that converts androgens to oestrogens, has been reported in glial cells and GB cell lines. Thus, it was necessary to test whether the steroidogenic enzymes involved in androgen synthesis are expressed in GB cells. Therefore, here, we investigated the expression of four key enzymes involved in androgen synthesis in human-derived GB cells. U87 cells were cultured in Dulbecco's modified Eagle medium plus foetal bovine serum and antibiotics on slides for immunocytochemistry or immunofluorescence. U87, LN229 and C6 cells were also cultured in multi-well chambers to obtain proteins for Western blotting. We used primary antibodies against 3ß-hydroxysteroid dehydrogenase (3ß-HSD), 17α-hydroxilase/17,20-lyase (P450c17), 17ß-hydroxysteroid dehydrogenase (17ß-HSD) and 5α-reductase. Immunocytochemistry, and immunofluorescence results revealed that glioblastoma cells express 3ß-HSD, P450c17, 17ß-HSD and 5α-reductase proteins in their cytoplasm. Moreover, Western blot analyses revealed bands corresponding to the molecular weight of these four enzymes in the three GB cell lines. Thus, glioblastoma cells have the key enzymatic machinery necessary to synthesize androgens, and these enzymes might be useful targets for new therapeutic approaches.

Neuroendocrine Mechanisms Underlying Non-breeding Aggression: Common Strategies Between Birds and Fish.

Aggression is an adaptive behavior that plays an important role in gaining access to limited resources. Aggression may occur uncoupled from reproduction, thus offering a valuable context to further understand its neural and hormonal regulation. This review focuses on the contributions from song sparrows (Melospiza melodia) and the weakly electric banded knifefish (Gymnotus omarorum). Together, these models offer clues about the underlying mechanisms of non-breeding aggression, especially the potential roles of neuropeptide Y (NPY) and brain-derived estrogens. The orexigenic NPY is well-conserved between birds and teleost fish, increases in response to low food intake, and influences sex steroid synthesis. In non-breeding M. melodia, NPY increases in the social behavior network, and NPY-Y1 receptor expression is upregulated in response to a territorial challenge. In G. omarorum, NPY is upregulated in the preoptic area of dominant, but not subordinate, individuals. We hypothesize that NPY may signal a seasonal decrease in food availability and promote non-breeding aggression. In both animal models, non-breeding aggression is estrogen-dependent but gonad-independent. In non-breeding M. melodia, neurosteroid synthesis rapidly increases in response to a territorial challenge. In G. omarorum, brain aromatase is upregulated in dominant but not subordinate fish. In both species, the dramatic decrease in food availability in the non-breeding season may promote non-breeding aggression, via changes in NPY and/or neurosteroid signaling.

The Role of HPA Axis and Allopregnanolone on the Neurobiology of Major Depressive Disorders and PTSD.

Under stressful conditions, the hypothalamic-pituitary-adrenal (HPA) axis acts to promote transitory physiological adaptations that are often resolved after the stressful stimulus is no longer present. In addition to corticosteroids (e.g., cortisol), the neurosteroid allopregnanolone (3α,5α-tetrahydroprogesterone, 3α-hydroxy-5α-pregnan-20-one) participates in negative feedback mechanisms that restore homeostasis. Chronic, repeated exposure to stress impairs the responsivity of the HPA axis and dampens allopregnanolone levels, participating in the etiopathology of psychiatric disorders, such as major depressive disorder (MDD) and post-traumatic stress disorder (PTSD). MDD and PTSD patients present abnormalities in the HPA axis regulation, such as altered cortisol levels or failure to suppress cortisol release in the dexamethasone suppression test. Herein, we review the neurophysiological role of allopregnanolone both as a potent and positive GABAergic neuromodulator but also in its capacity of inhibiting the HPA axis. The allopregnanolone function in the mechanisms that recapitulate stress-induced pathophysiology, including MDD and PTSD, and its potential as both a treatment target and as a biomarker for these disorders is discussed.

Therapeutic Potential of GABAergic Signaling in Myelin Plasticity and Repair.

Oligodendrocytes (OLs) produce myelin to insulate axons. This accelerates action potential propagation, allowing nerve impulse information to synchronize within complex neuronal ensembles and promoting brain connectivity. Brain plasticity includes myelination, a process that starts early after birth and continues throughout life. Myelin repair, followed by injury or disease, requires new OLs differentiated from a population derived from oligodendrocyte precursor cells (OPCs) that continue to proliferate, migrate and differentiate to preserve and remodel myelin in the adult central nervous system. OPCs represent the largest proliferative neural cell population outside the adult neurogenic niches in the brain. OPCs receive synaptic inputs from glutamatergic and GABAergic neurons throughout neurodevelopment, a unique feature among glial cells. Neuron-glia communication through GABA signaling in OPCs has been shown to play a role in myelin plasticity and repair. In this review we will focus on the molecular and functional properties of GABA A receptors (GABA A Rs) expressed by OPCs and their potential role in remyelination.

Neuroprotective Effects of Testosterone in Male Wobbler Mouse, a Model of Amyotrophic Lateral Sclerosis.

Patients suffering of amyotrophic lateral sclerosis (ALS) present motoneuron degeneration leading to muscle atrophy, dysphagia, and dysarthria. The Wobbler mouse, an animal model of ALS, shows a selective loss of motoneurons, astrocytosis, and microgliosis in the spinal cord. The incidence of ALS is greater in men; however, it increases in women after menopause, suggesting a role of sex steroids in ALS. Testosterone is a complex steroid that exerts its effects directly via androgen (AR) or Sigma-1 receptors and indirectly via estrogen receptors (ER) after aromatization into estradiol. Its reduced-metabolite 5α-dihydrotestosterone acts via AR. This study analyzed the effects of testosterone in male symptomatic Wobblers. Controls or Wobblers received empty or testosterone-filled silastic tubes for 2 months. The cervical spinal cord from testosterone-treated Wobblers showed (1) similar androgen levels to untreated control and (2) increased levels of testosterone, and its 5α-reduced metabolites, 5α- dihydrotestosterone, and 3ß-androstanediol, but (3) undetectable levels of estradiol compared to untreated Wobblers. Testosterone-treated controls showed comparable steroid concentrations to its untreated counterpart. In testosterone- treated Wobblers a reduction of AR, ERα, and aromatase and high levels of Sigma-1 receptor mRNAs was demonstrated. Testosterone treatment increased ChAT immunoreactivity and the antiinflammatory mediator TGFß, while it lessened vacuolated motoneurons, GFAP+ astrogliosis, the density of IBA1+ microgliosis, proinflammatory mediators, and oxidative/nitrosative stress. Clinically, testosterone treatment in Wobblers slowed the progression of paw atrophy and improved rotarod performance. Collectively, our findings indicate an antiinflammatory and protective effect of testosterone in the degenerating spinal cord. These results coincided with a high concentration of androgen-reduced derivatives after testosterone treatment suggesting that the steroid profile may have a beneficial role on disease progression.

Developmental expression of genes involved in progesterone synthesis, metabolism and action during the post-natal cerebellar myelination.

Progesterone is involved in dendritogenesis, synaptogenesis and maturation of cerebellar Purkinge cells, major sites of steroid synthesis in the brain. To study a possible time-relationship between myelination, neurosteroidogenesis and steroid receptors during development of the postnatal mouse cerebellum, we determined at postnatal days 5 (P5),18 (P18) and 35 (P35) the expression of myelin basic protein (MBP), components of the steroidogenic pathway, levels of endogenous steroids and progesterone's classical and non-classical receptors. In parallel with myelin increased expression during development, P18 and P35 mice showed higher levels of cerebellar progesterone and its reduced derivatives, higher expression of steroidogenic acute regulatory protein (StAR) mRNA, cholesterol side chain cleavage enzyme (P450scc) and 5α-reductase mRNA vs. P5 mice. Other steroids such as corticosterone and its reduced derivatives and 3ß-androstanodiol (ADIOL) showed a peak increase at P18 compared to P5. Progesterone membrane receptors and binding proteins (PGRMC1, mPRα, mPRß, mPRγ, and Sigma1 receptors) mRNAs levels increased during development while that of classical progesterone receptors (PR) remained invariable. PRKO mice showed similar MBP levels than wild type. Thus, these data suggests that progesterone and its neuroactive metabolites may play a role in postnatal cerebellar myelination.

Síndrome do mau ajustamento neonatal em potros: foco em neuroesteróides / Foal mal adjustment syndrome: focus on neurosteroids

O processo de transição do feto para a vida extra-uterina é considerado um período crítico que requer complexas adaptações fisiológicas do potro neonato. Eventos estressores de origem hipóxicoisquêmicas no periparto podem desencadear um quadro de encefalopatia neonatal equina, também conhecida como síndrome do mau ajustamento neonatal. O diagnóstico é feito baseado na avaliação clínica e na anamnese e avaliação do histórico da gestação. Casos leves a moderados tem prognóstico favorável. É imprescindível o entendimento da endocrinologia da gestação, do papel dos neuroesteróides no desenvolvimento do sistema nervoso fetal para que o estabelecimento precoce da terapia adequada seja realizado de maneira bem sucedida. Assim, o objetivo do presente é abordar os principais aspectos clínicos e fisiopatológicos da Síndrome do Mau Ajustamento Neonatal em neonatos equinos, com foco especial no papel dos neuroesteróides durante a maturação cerebral do feto no terço final da gestação e na transição para a vida extra-uterina.

The transition from fetus to extrauterine life is considered a critical period that requires complex physiological adaptations on the part of the newborn foal. Peripartum hypoxic-ischemic stressors can result in equine neonatal encephalopathy, also known to as neonatal maladjustment syndrome. The diagnosis is made based on clinical examination, anamnesis, and a review of the mare’s pregnancy history. Cases that are mild to moderate in severity have a favorable prognosis. It is critical to understand the endocrinology of pregnancy and the role of neurosteroids in the development of the fetal nervous system in order to successfully initiate appropriate therapy early. Thus, the purpose of this article is to discuss the major clinical and pathophysiological aspects of neonatal maladjustment syndrome in equine neonates, with a particular emphasis on the role of neurosteroids during fetal brain maturation in the final third of pregnancy and during the transition to extrauterine life.

Lipotoxicity, neuroinflammation, glial cells and oestrogenic compounds.

The high concentrations of free fatty acids as a consequence of obesity and being overweight have become risk factors for the development of different diseases, including neurodegenerative ailments. Free fatty acids are strongly related to inflammatory events, causing cellular and tissue alterations in the brain, including cell death, deficits in neurogenesis and gliogenesis, and cognitive decline. It has been reported that people with a high body mass index have a higher risk of suffering from Alzheimer's disease. Hormones such as oestradiol not only have beneficial effects on brain tissue, but also exert some adverse effects on peripheral tissues, including the ovary and breast. For this reason, some studies have evaluated the protective effect of oestrogen receptor (ER) agonists with more specific tissue activities, such as the neuroactive steroid tibolone. Activation of ERs positively affects the expression of pro-survival factors and cell signalling pathways, thus promoting cell survival. This review aims to discuss the relationship between lipotoxicity and the development of neurodegenerative diseases. We also elaborate on the cellular and molecular mechanisms involved in neuroprotection induced by oestrogens.

Allopregnanolone and Progesterone in Experimental Neuropathic Pain: Former and New Insights with a Translational Perspective.

In the last decades, an active and stimulating area of research has been devoted to explore the role of neuroactive steroids in pain modulation. Despite challenges, these studies have clearly contributed to unravel the multiple and complex actions and potential mechanisms underlying steroid effects in several experimental conditions that mimic human chronic pain states. Based on the available data, this review focuses mainly on progesterone and its reduced derivative allopregnanolone (also called 3α,5α-tetrahydroprogesterone) which have been shown to prevent or even reverse the complex maladaptive changes and pain behaviors that arise in the nervous system after injury or disease. Because the characterization of new related molecules with improved specificity and enhanced pharmacological profiles may represent a crucial step to develop more efficient steroid-based therapies, we have also discussed the potential of novel synthetic analogs of allopregnanolone as valuable molecules for the treatment of neuropathic pain.

Steroid Hormones and Their Action in Women's Brains: The Importance of Hormonal Balance.

Sex hormones significantly impact women's lives. Throughout the different stages of life, from menarche to menopause and all stages in between, women experience dramatic fluctuations in the levels of progesterone and estradiol, among other hormones. These fluctuations affect the body as a whole, including the central nervous system (CNS). In the CNS, sex hormones act via steroid receptors. They also have an effect on different neurotransmitters such as GABA, serotonin, dopamine, and glutamate. Additionally, studies show that sex hormones and their metabolites influence brain areas that regulate mood, behavior, and cognitive abilities. This review emphasizes the benefits a proper hormonal balance during the different stages of life has in the CNS. To achieve this goal, it is essential that hormone levels are evaluated considering a woman's age and ovulatory status, so that a correct diagnosis and treatment can be made. Knowledge of steroid hormone activity in the brain will give women and health providers an important tool for improving their health and well-being.

Sex steroid hormones as neuroprotective elements in ischemia models.

Among sex steroid hormones, progesterone and estradiol have a wide diversity of physiological activities that target the nervous system. Not only are they carried by the blood stream, but also they are locally synthesized in the brain and for this reason, estradiol and progesterone are considered 'neurosteroids'. The physiological actions of both hormones range from brain development and neurotransmission to aging, illustrating the importance of a deep understanding of their mechanisms of action. In this review, we summarize key roles that estradiol and progesterone play in the brain. As numerous reports have confirmed a substantial neuroprotective role for estradiol in models of neurodegenerative disease, we focus this review on traumatic brain injury and stroke models. We describe updated data from receptor and signaling events triggered by both hormones, with an emphasis on the mechanisms that have been reported as 'rapid' or 'cytoplasmic actions'. Data showing the therapeutic effects of the hormones, used alone or in combination, are also summarized, with a focus on rodent models of middle cerebral artery occlusion (MCAO). Finally, we draw attention to evidence that neuroprotection by both hormones might be due to a combination of 'cytoplasmic' and 'nuclear' signaling.

Efficient breathing at neonatal ages: A sex and Epo-dependent issue.

During postnatal life, the respiratory control system undergoes intense development and is highly responsive to stimuli emerging from the environment. In fact, interruption of breathing prevents gas exchange and results in systemic hypoxia that, if prolonged, can lead to cardio-respiratory failure or sudden infant death. Moreover, in newborns and infants, respiratory disorders related to neural control dysfunction show significant sexual dimorphism with a higher prevalence in males. To this day, the therapeutic tools available to alleviate these respiratory disorders remain limited. Furthermore, the factors explaining the sexual dimorphism in newborns and during infancy remain unknown. Erythropoietin (Epo) was originally discovered as a cytokine able to increase the production of red blood cells upon conditions of reduced oxygen availability. We now know that Epo is a cytokine also secreted by neurons and astrocytes that protects the brain during trauma or hypoxic stress in a sex dependent manner. In this novel line of research, our previous studies demonstrated at adult ages that cerebral Epo acts as a respiratory stimulant in rodents and humans. These results provided a strong rationale for exploring the role of cerebral Epo in neuronal respiratory control during postnatal development. The objective of this review is to summarize our recent findings showing that cerebral Epo is a potent sex-specific respiratory stimulant at neonatal ages. Keeping in mind that Epo is routinely and safely administrated in newborn humans for anemia and neonatal asphyxia, we predict that our research provides the basis necessary to promote the clinical use of Epo against neonatal respiratory disorders related to neural control dysfunction.

Neuroactive steroids, nociception and neuropathic pain: A flashback to go forward.

The present review discusses the potential role of neurosteroids/neuroactive steroids in the regulation of nociceptive and neuropathic pain, and recapitulates the current knowledge on the main mechanisms involved in the reduction of pain, especially those occurring at the dorsal horn of the spinal cord, a crucial site for nociceptive processing. We will make special focus on progesterone and its derivative allopregnanolone, which have been shown to exert remarkable actions in order to prevent or reverse the maladaptive changes and pain behaviors that arise after nervous system damage in various experimental neuropathic conditions.

Novel Approaches in Astrocyte Protection: from Experimental Methods to Computational Approaches.

Astrocytes are important for normal brain functioning. Astrocytes are metabolic regulators of the brain that exert many functions such as the preservation of blood-brain barrier (BBB) function, clearance of toxic substances, and generation of antioxidant molecules and growth factors. These functions are fundamental to sustain the function and survival of neurons and other brain cells. For these reasons, the protection of astrocytes has become relevant for the prevention of neuronal death during brain pathologies such as Parkinson's disease, Alzheimer's disease, stroke, and other neurodegenerative conditions. Currently, different strategies are being used to protect the main astrocytic functions during neurological diseases, including the use of growth factors, steroid derivatives, mesenchymal stem cell paracrine factors, nicotine derivatives, and computational biology tools. Moreover, the combined use of experimental approaches with bioinformatics tools such as the ones obtained through system biology has allowed a broader knowledge in astrocytic protection both in normal and pathological conditions. In the present review, we highlight some of these recent paradigms in assessing astrocyte protection using experimental and computational approaches and discuss how they could be used for the study of restorative therapies for the brain in pathological conditions.

Sex chromosome complement determines sex differences in aromatase expression and regulation in the stria terminalis and anterior amygdala of the developing mouse brain.

Aromatase, which converts testosterone in estradiol, is involved in the generation of brain sex dimorphisms. Here we used the "four core genotypes" mouse model, in which the effect of gonadal sex and sex chromosome complement is dissociated, to determine if sex chromosomes influence the expression of brain aromatase. The brain of 16 days old XY mouse embryos showed higher aromatase expression in the stria terminalis and the anterior amygdaloid area than the brain of XX embryos, independent of gonadal sex. Furthermore, estradiol or dihydrotestosterone increased aromatase expression in cultures of anterior amygdala neurons derived from XX embryos, but not in those derived from XY embryos. This effect was also independent of gonadal sex. The expression of other steroidogenic molecules, estrogen receptor-α and androgen receptor was not influenced by sex chromosomes. In conclusion, sex chromosomes determine sex dimorphisms in aromatase expression and regulation in the developing mouse brain.

Trastornos hormonales en pacientes con epilepsia / Hormonal Disorders in Patients with Epilepsy

La epilepsia es una de las enfermedades neurológicas crónicas más comunes cuya etiología es multifactorial (congénita, traumatismos, infecciones en el sistema nervioso central, etc.). Existen varias interacciones multidireccionales entre ejes hormonales, crisis epilépticas y la utilización de medicación destinada para su control. Las alteraciones en los niveles endógenos o exógenos de hormonas pueden afectar la excitabilidad neuronal y la susceptibilidad a crisis o indirectamente a través de alteraciones en las concentraciones de drogas antiepilépticas e inversamente anormalidades estructurales y fisiológicas del cerebro afectado por la epilepsia o su medicación pueden afectar los diferentes ejes hipotálamo-hipofisarios.

Epilepsy is one of the most common chronic neurological diseases with multifactorial etiology (congenital, trauma, central nervous system infection, etc.). There are several multidirectional interactions between hormonal axes, seizures and the use of medication to control this disease. For example, alterations in endogenous or exogenous hormonal levels can directly affect neuronal excitability as well as susceptibility to crises or indirectly through changes in the concentrations of antiepileptic drugs and, conversely, structural and physiological abnormalities of the brain affected by epilepsy or medication can affect the different hypothalamic-pituitary axes.

Effect of synthetic steroids on GABAA receptor binding in rat brain.

Neuroactive steroids, like allopregnanolone (A) and pregnanolone (P), bind to specifics sites on the GABAA receptor complex and modulate receptor function. They are capable to inhibit or stimulate the binding of GABAA receptor-specific ligands, like t-butyl-bicyclophosphorothionate, flunitrazepam and muscimol. We have previously characterized a set of oxygen-bridged synthetic steroids (SS) analogs to A or P using synaptosomes. Considering that the subunit composition of the GABAA receptor throughout the central nervous system affects the magnitude of the modulation of the GABAA receptor by NAS, we evaluated the action of two selected SS, in brain sections containing the cerebral cortex (CC) and hippocampus (HC) using quantitative receptor autoradiography. Both SS affected the binding of the three ligands in a similar way to A and P, with some differences on certain CC layers according to the ligand used. One of the SS, the 3α-hydroxy-6,19-epoxypregn-4-ene-20-one (compound 5), behaved similarly to the natural neuroactive steroids. However, significant differences with compound 5 were observed on the HC CA2 region, making it steroid suitable for a specific action. Those differences may be related to structural conformation of the SS and the subunits' composition present on the receptor complex.

Neuroprotective action of synthetic steroids with oxygen bridge. Activity on GABAA receptor.

Allopregnanolone (A) and pregnanolone (P) are able to modify neural activities acting through the GABAA receptor complex. This capacity makes them useful as anticonvulsant, anxiolytic, or anti-stress compounds. In this study, the performance of seven synthetic steroids (SS) analogous of A or P containing an intramolecular oxygen bridge was evaluated using different assays. Competition assays showed that compounds 1, 5, 6 and 7 affected the binding of specific ligands for the GABAA receptor in a way similar to that of A and P, whereas compounds 3 and 4 stimulated [(3)H]-flunitrazepam and reduced [(35)S]-TBPS binding. The enzyme 3ß-hydroxysteroid dehydrogenase (3ß-HSD) produces the precursor for A and P, and its activity is regulated by steroids. The action of several SS on 3ß-HSD activity was tested in different tissues. All SS analyzed inhibit its activity, but compound 5 was the least effective. Finally, the neuroprotective role of two SS was evaluated in cerebral cortex and hippocampus cultures subjected to hypoxia. Glial fibrillary acidic protein (GFAP) increase was prevented by A, P, and compounds 3 and 5. Only A, P and compound 5 prevented neurofilament (NF160/200) decrease in hippocampus cultures, whereas A and compound 5 partially prevented NF200 and NF160 decreases respectively in cerebral cortex cultures. A prevented microtubule associated protein (MAP 2b) decrease in cerebral cortex cultures, while in hippocampus cultures only compounds 3 and 5 had effect. All steroids prevented MAP 2c decrease in both brain regions.