Testosterone modulation of seizure susceptibility is mediated by neurosteroids 3α-androstanediol and 17β-estradiol

Neurosteroids: A potential target for neuropsychiatric disorders

Neurosteroids are steroids produced by endocrine glands and subsequently entering the brain, and also include steroids synthesis in the brain. It has been widely known that neurosteroids influence many neurological functions, including neuronal signaling, synaptic adaptations, and neuroprotective effects. In addition, abnormality in the synthesis and function of neurosteroids has been closely linked to neuropsychiatric disorders, such as Alzheimer's disease (AD), schizophrenia (SZ), and epilepsy. Given their important role in brain pathophysiology and disorders, neurosteroids offer potential therapeutic targets for a variety of neuropsychiatric diseases, and that therapeutic strategies targeting neurosteroids probably exert beneficial effects. We therefore summarized the role of neurosteroids in brain physiology and neuropsychiatric disorders, and introduced the recent findings of synthetic neurosteroid analogues for potential treatment of neuropsychiatric disorders, thereby providing insights for further research in the future.

Sex and gonadectomy modify behavioral seizure susceptibility and mortality in a repeated low-dose kainic acid systemic injection paradigm in mice

OBJECTIVE

Sex differences in epilepsy appear driven in part due to effects of gonadal steroids, with varying results in experimental models based on species, strain, and method of seizure induction. Furthermore, removing the main source of these steroids via gonadectomy may impact seizure characteristics differently in males and females. Repeated low-dose kainic acid (RLDKA) systemic injection paradigms were recently shown to reliably induce status epilepticus (SE) and hippocampal histopathology in C57BL/6J mice. Here, we investigated whether seizure susceptibility in a RLDKA injection protocol exhibits a sex difference and whether gonadectomy differentially influences response to this seizure induction paradigm in males and females.

METHODS

Adult C57BL/6J mice were left gonad-intact as controls or gonadectomized (females: ovariectomized, OVX; males: orchidectomized, ORX). At least 2 weeks later, KA was injected ip, every 30 minutes at 7.5 mg/kg or less until the animal reached SE, defined by at least 5 generalized seizures (GS, Racine stage 3 or higher). Parameters of susceptibility to GS induction, SE development, and mortality rates were quantified.

RESULTS

No differences in seizure susceptibility or mortality were observed between control males and control females. Gonadectomized mice exhibited increased susceptibility and reduced latency to both GS and SE in comparison to corresponding controls of the same sex, but the effects were stronger in males. In addition, ORX males, but not OVX females, exhibited strongly increased seizure-induced mortality.

SIGNIFICANCE

The RLDKA protocol is notable for its efficacy in inducing SE and seizure-induced histopathology in C57BL/6J mice, the background for many transgenic strains in current use in epilepsy research. The present results indicate that this protocol may be beneficial for investigating the effects of gonadal hormone replacement on seizure susceptibility, mortality, and seizure-induced histopathology, and that gonadectomy unmasks sex differences in susceptibility to seizures and mortality not observed in gonad-intact controls.

Androgen insensitivity syndrome: a review

PURPOSE

Androgen insensitivity syndrome (AIS) is a disorder characterized by peripheral androgen resistance due to androgen receptor mutations in subjects with 46 XY karyotype. The severity of hormone resistance (complete, partial or mild) determines the wide spectrum of phenotypes.

METHODS

We performed a literature review on Pubmed focusing on etiopathogenesis, molecular alterations, and diagnostic-therapeutic management.

RESULTS

AIS is determined by a large variety of X-linked mutations that account for the wide phenotypic spectrum of subjects; it represents one of the most frequent disorders of sexual development (DSD). Clinical suspicion can arise at birth in partial AIS, due to the presence of variable degrees of ambiguity of the external genitalia, and at pubertal age in complete AIS, due to the development of female secondary sex characteristics, primary amenorrhea, and absence of female primary sex characteristics (uterus and ovaries). Laboratory tests showing elevated LH and testosterone levels despite mild or absent virilization may be helpful, but diagnosis can be achieved only after genetic testing (karyotype examination and androgen receptor sequencing). The clinical phenotype and especially the decision on sex assignment of the patient, if the diagnosis is made at birth or in the neonatal period, will guide the following medical, surgical and psychological management.

CONCLUSIONS

For the management of AIS, a multidisciplinary team consisting of physicians, surgeons, and psychologists is highly recommended to support the patient and his/her family on gender identity choices and subsequent appropriate therapeutic decisions.

Sex and gonadectomy modify behavioral seizure susceptibility and mortality in a repeated low-dose kainic acid systemic injection paradigm in mice

Objective

Sex differences in epilepsy appear driven in part due to effects of gonadal steroids, with varying results in experimental models based on species, strain, and method of seizure induction. Furthermore, removing a main source of these steroids via gonadectomy may impact seizure characteristics differently in males and females. Repeated low-dose kainic acid (RLDKA) systemic injection paradigms were recently shown to reliably induce status epilepticus (SE) and hippocampal histopathology in C57BL/6J mice. Here, we investigated whether seizure susceptibility in a RLDKA injection protocol exhibits a sex difference, and whether gonadectomy differentially influences response to this seizure induction paradigm in males and females.

Methods

Adult C57BL/6J mice were left gonad-intact as controls or gonadectomized (females: ovariectomized, OVX; males: orchidectomized, ORX). At least 2 weeks later, KA was injected i.p. every 30 minutes at 7.5 mg/kg or less until the animal reached SE, defined by at least 5 generalized seizures (GS, Racine stage 3 or higher). Parameters of susceptibility to GS induction, SE development, and mortality rates were quantified.

Results

No differences in seizure susceptibility or mortality were observed between control males and control females. ORX males exhibited increased susceptibility and reduced latency to both GS and SE, but OVX females exhibited increased susceptibility and reduced latency to SE only. However, ORX males, but not OVX females, exhibited strongly increased seizure-induced mortality.

Significance

The RLDKA protocol is notable for its efficacy in inducing SE and seizure-induced histopathology in C57BL/6J mice, the background for many transgenic strains in current use in epilepsy research. The present results indicate that this protocol may be beneficial for investigating the effects of gonadal hormone replacement on seizure susceptibility, mortality, and seizure-induced histopathology, and that gonadectomy unmasks sex differences in susceptibility to seizures and mortality not observed in gonad-intact controls.

Androgens and Selective Androgen Receptor Modulators to Treat Functional Limitations Associated With Aging and Chronic Disease

Testosterone, many steroidal androgens, and nonsteroidal ligands that bind to androgen receptor and exert tissue-specific transcriptional activity (selective androgen receptor modulators [SARMs]) are being developed as function-promoting therapies to treat functional limitations associated with aging and chronic diseases. This narrative review describes preclinical studies, mechanisms, and randomized trials of testosterone, other androgens, and nonsteroidal SARMs. Sex differences in muscle mass and strength and empiric use of anabolic steroids by athletes to increase muscularity and athletic performance provide supportive evidence of testosterone's anabolic effects. In randomized trials, testosterone treatment increases lean body mass, muscle strength, leg power, aerobic capacity, and self-reported mobility. These anabolic effects have been reported in healthy men, hypogonadal men, older men with mobility limitation and chronic diseases, menopausal women, and HIV-infected women with weight loss. Testosterone has not consistently improved walking speed. Testosterone treatment increases volumetric and areal bone mineral density, and estimated bone strength; improves sexual desire, erectile function, and sexual activity; modestly improves depressive symptoms; and corrects unexplained anemia in older men with low testosterone levels. Prior studies have not been of sufficient size or duration to determine testosterone's cardiovascular and prostate safety. The efficacy of testosterone in reducing physical limitations, fractures, falls, progression to diabetes, and correcting late-onset persistent depressive disorder remains to be established. Strategies to translate androgen-induced muscle mass and strength gains into functional improvements are needed. Future studies should evaluate the efficacy of combined administration of testosterone (or a SARM) plus multidimensional functional exercise to induce neuromuscular adaptations required for meaningful functional improvements.

Neurosteroids as positive and negative allosteric modulators of ligand-gated ion channels: P2X receptor perspective

Neurosteroids are steroids synthesized de novo in the brain from cholesterol in an independent manner from peripheral steroid sources. The term "neuroactive steroid" includes all steroids independent of their origin, and newly synthesized analogs of neurosteroids that modify neuronal activities. In vivo application of neuroactive steroids induces potent anxiolytic, antidepressant, anticonvulsant, sedative, analgesic and amnesic effects, mainly through interaction with the γ-aminobutyric acid type-A receptor (GABA_AR). However, neuroactive steroids also act as positive or negative allosteric regulators on several ligand-gated channels including N-methyl-d-aspartate receptors (NMDARs), nicotinic acetylcholine receptors (nAChRs) and ATP-gated purinergic P2X receptors. Seven different P2X subunits (P2X1-7) can assemble to form homotrimeric or heterotrimeric ion channels permeable for monovalent cations and calcium. Among them, P2X2, P2X4, and P2X7 are the most abundant within the brain and can be regulated by neurosteroids. Transmembrane domains are necessary for neurosteroid binding, however, no generic motif of amino acids can accurately predict the neurosteroid binding site for any of the ligand-gated ion channels including P2X. Here, we will review what is currently known about the modulation of rat and human P2X by neuroactive steroids and the possible structural determinants underlying neurosteroid-induced potentiation and inhibition of the P2X2 and P2X4 receptors.

Determinants of quality of life in Nigerian female patients with epilepsy on carbamazepine and levetiracetam monotherapy

Background

The study is aimed to identify the predictors of Quality of Life (QOL) in women with epilepsy (WWE) on carbamazepine (CBM) and levetiracetam (LTM) monotherapy. 100 WWE were recruited (50 each on CBM and LTM), after clinical diagnosis of epilepsy supported by Electroencephalography (EEG) features and seizures classification by 2017 International League Against Epilepsy (ILAE) criteria, the Quality of Life Inventory Scale 31(QOLIE-31) and Zung Self-Rating Depression Scale (ZSRDS) were used to assess QOL and depression, respectively.

Result

Higher QOLIE-31 scores was seen in the LTM group across all domains except seizure worry (p = 0.051) compared to CBM group. Logistic regression showed that the use of CBM (p = 0.000), fast frequency on EEG (p = 0.005), longer duration of epilepsy (p = 0.017), presence of depression (p = 0.008) and lower level of education (p = 0.003) were predictors of QOL. Progesterone (p = 0.040), oestradiol (p = 0.011) and prolactin (p = 0.002) in follicular phase showed significant association with QOLIE-total score. In the luteal phase, luteinizing hormone–follicle stimulating hormone (LH–FSH) ratio (p = 0.009) and testosterone (p = 0.015), FSH (p = 0.015), prolactin (p = 0.000), showed significant association with QOL. None of the hormones independently predicts QOL.

Conclusion

LTM group appears to have better QOL than CBM group. Healthcare providers should focus on addressing these identified predictors which include medication effect, depression, Level of education, EEG background and duration of epilepsy with aim of improving QOL.

Sex hormones and risk of epilepsy: A bidirectional Mendelian randomization study

Background

Multiple evidence has suggested complex interaction between sex hormones and epilepsy. However, whether there exists a causal association and the effect direction remains controversial. Here we aimed to examine the causative role of hormones in the risk of epilepsy and vice versa.

Methods

We conducted a bidirectional two-sample Mendelian randomization analysis using summary statistics from genome-wide association studies of major sex hormones including testosterone (N = 425,097), estradiol (N = 311,675) and progesterone (N = 2,619), together with epilepsy (N = 44,889). We further performed sex-stratified analysis, and verified the significant results using summary statistics from another study on estradiol in males (N = 206,927).

Results

Genetically determined higher estradiol was associated with a reduced risk of epilepsy (OR: 0.90, 95% CI: 0.83-0.98, P = 9.51E-03). In the sex-stratified analysis, the protective effect was detected in males (OR: 0.92, 95% CI: 0.88-0.97, P = 9.18E-04), but not in females. Such association was further verified in the replication stage (OR: 0.44, 95% CI: 0.23-0.87, P = 0.017). In contrast, no association was identified between testosterone, progesterone and the risk of epilepsy. In the opposite direction, epilepsy was not causally associated with sex hormones.

Conclusion

These results demonstrated higher estradiol could reduce the risk of epilepsy, especially in males. Future development of preventive or therapeutic interventions in clinical trials could attach importance to this.

Ferulic acid inhibits catamenial epilepsy through modulation of female hormones

Approximately 40% of women with epilepsy experience perimenstrual seizure exacerbation, referred to as catamenial epilepsy. These seizures result from cyclic changes in circulating progesterone and estradiol levels and there is no effective treatment for this form of intractable epilepsy. We artificially increased progesterone levels and neurosteroid levels (pseudo-pregnancy) in adult Swiss albino female mice (19-23 g) by injecting them with pregnant mares' serum gonadotropin (5 IU s.c.), followed by human chorionic gonadotropin (5 IU s.c.) after 46 h. After this, ferulic acid (25, 50, 100 mg/kg i.p.) treatment was given for 10 days. During treatment, progesterone, estradiol, and corticosterone levels were estimated in blood on days 1, 5, and 10. Neurosteroid withdrawal was induced by finasteride (50 mg/kg, i.p.) on treatment day 9. Twenty-four hours after finasteride administration (day 10 of treatment), seizure susceptibility was evaluated with the sub-convulsant pentylenetetrazol (PTZ) dose (40 mg/kg i.p.). Four to six hours after PTZ, animals were assessed for depression like phenotypes using tail-suspension test (TST). Four to six hours following TST, animals were euthanized, and discrete brain parts (cortex and hippocampus) were separated for estimation of norepinephrine, serotonin, and dopamine as well as glutamic acid decarboxylase (GAD) enzyme activity. PMSG and HCG treatment elevated progesterone and estradiol levels, assessed on days 1, 5, and 10 causing a state of pseudo-pregnancy. Treatment with finasteride increased seizure susceptibility and depression-like characteristics possibly due to decreased progesterone and elevated estrogen levels coupled with decreased monoamine and elevated corticosterone levels. Ferulic acid treatment, on the other hand, significantly decreased seizure susceptibility and depression like behavior, possibly because of increased progesterone, restored estradiol, corticosterone, monoamines, and GAD enzyme activity. We concluded anticonvulsant effect of ferulic acid in a mouse model of catamenial epilepsy, evidenced by favourable seizure attenuation and curative effect on the circulating progesterone, estradiol, and corticosterone levels along with restorative effect on GAD enzyme activity and monoamine levels.

Metabolic effects of estradiol versus testosterone in complete androgen insensitivity syndrome

PURPOSE

To study differences in metabolic outcomes between testosterone and estradiol replacement in probands with complete androgen insensitivity syndrome (CAIS).

METHODS

In this multicentre, double-blind, randomized crossover trial, 26 women with CAIS were included of whom 17 completed the study. After a two-months run in phase with estradiol, probands either received transdermal estradiol followed by crossover to transdermal testosterone or vice versa. After six months, differences in lipids, fasting glucose, insulin, hematocrit, liver parameters and blood pressure between the treatment phases were investigated.

RESULTS

Linear mixed models adjusted for period and sequence did not reveal major group differences according to treatment for the investigated outcomes. In each treatment group, there were however significant uniform changes in BMI and cholesterol. BMI increased significantly, following six months of estradiol ( + 2.7%; p = 0.036) as well as testosterone treatment ( + 2.8%; p = 0.036). There was also a significant increase in total ( + 10.4%; p = 0.001) and LDL-cholesterol ( + 29.2%; p = 0.049) and a decrease in HDL-cholesterol (-15.8%; p < 0.001) following six months of estradiol as well as six months of testosterone treatment (total cholesterol: + 14.6%; p = 0.008; LDL-cholesterol: + 39.1%; p = 0.005, HDL-cholesterol: -15.8%; p = 0.004). Other parameters remained unchanged.

CONCLUSION

Transdermal estradiol as well as testosterone treatment in women with CAIS results in worsening in lipid profiles. Given the relatively small sample size, subtle group differences in other metabolic parameters may have remained undetected.

Effects of sex hormones on brain GABA and glutamate levels in a cis- and transgender cohort

Sex hormones affect the GABAergic and glutamatergic neurotransmitter system as demonstrated in animal studies. However, human research has mostly been correlational in nature. Here, we aimed at substantiating causal interpretations of the interaction between sex hormones and neurotransmitter function by using magnetic resonance spectroscopy imaging (MRSI) to study the effect of gender-affirming hormone treatment (GHT) in transgender individuals. Fifteen trans men (TM) with a DSM-5 diagnosis of gender dysphoria, undergoing GHT, and 15 age-matched cisgender women (CW), receiving no therapy, underwent MRSI before and after at least 12 weeks. Additionally, sex differences in neurotransmitter levels were evaluated in an independent sample of 80 cisgender men and 79 cisgender women. Mean GABA+ (combination of GABA and macromolecules) and Glx (combination of glutamate and glutamine) ratios to total creatine (GABA+/tCr, Glx/tCr) were calculated in five predefined regions-of-interest (hippocampus, insula, pallidum, putamen and thalamus). Linear mixed models analysis revealed a significant measurement by gender identity effect (p_corr. = 0.048) for GABA+/tCr ratios in the hippocampus, with the TM cohort showing decreased GABA+/tCr levels after GHT compared to CW. Moreover, analysis of covariance showed a significant sex difference in insula GABA+/tCr ratios (p_corr. = 0.049), indicating elevated GABA levels in cisgender women compared to cisgender men. Our study demonstrates GHT treatment-induced GABA+/tCr reductions in the hippocampus, indicating hormone receptor activation on GABAergic cells and testosterone-induced neuroplastic processes within the hippocampus. Moreover, elevated GABA levels in the female compared to the male insula highlight the importance of including sex as factor in future MRS studies. DATA AVAILABILITY STATEMENT: Due to data protection laws processed data is available from the authors upon reasonable request. Please contact rupert.lanzenberger@meduniwien.ac.at with any questions or requests.

Aromatase in the Human Brain

The aromatase cytochrome P450 (P450arom) enzyme, or estrogen synthase, which is coded by the CYP19A1 gene, is widely expressed in a subpopulation of excitatory and inhibitory neurons, astrocytes, and other cell types in the human brain. Experimental studies in laboratory animals indicate a prominent role of brain aromatization of androgens to estrogens in regulating different brain functions. However, the consequences of aromatase expression in the human brain remain poorly understood. Here, we summarize the current knowledge about aromatase expression in the human brain, abundant in the thalamus, amygdala, hypothalamus, cortex, and hippocampus and discuss its role in the regulation of sensory integration, body homeostasis, social behavior, cognition, language, and integrative functions. Since brain aromatase is affected by neurodegenerative conditions and may participate in sex-specific manifestations of autism spectrum disorders, major depressive disorder, multiple sclerosis, stroke, and Alzheimer's disease, we discuss future avenues for research and potential clinical and therapeutic implications of the expression of aromatase in the human brain.

Transcriptome of the Krushinsky-Molodkina Audiogenic Rat Strain and Identification of Possible Audiogenic Epilepsy-Associated Genes

Audiogenic epilepsy (AE), inherent to several rodent strains is widely studied as a model of generalized convulsive epilepsy. The molecular mechanisms that determine the manifestation of AE are not well understood. In the present work, we compared transcriptomes from the corpora quadrigemina in the midbrain zone, which are crucial for AE development, to identify genes associated with the AE phenotype. Three rat strains without sound exposure were compared: Krushinsky-Molodkina (KM) strain (100% AE-prone); Wistar outbred rat strain (non-AE prone) and “0” strain (partially AE-prone), selected from F2 KM × Wistar hybrids for their lack of AE. The findings showed that the KM strain gene expression profile exhibited a number of characteristics that differed from those of the Wistar and “0” strain profiles. In particular, the KM rats showed increased expression of a number of genes involved in the positive regulation of the MAPK signaling cascade and genes involved in the positive regulation of apoptotic processes. Another characteristic of the KM strain which differed from that of the Wistar and “0” rats was a multi-fold increase in the expression level of the Ttr gene and a significant decrease in the expression of the Msh3 gene. Decreased expression of a number of oxidative phosphorylation-related genes and a few other genes was also identified in the KM strain. Our data confirm the complex multigenic nature of AE inheritance in rodents. A comparison with data obtained from other independently selected AE-prone rodent strains suggests some common causes for the formation of the audiogenic phenotype.

Brain structural and neuroendocrine basis of sex differences in epilepsy

This chapter reviews the current information about sex differences in epilepsy and potential mechanisms underlying sex differences in seizure susceptibility and epilepsy. The susceptibility to and occurrence of seizures are generally higher in men than women. There is gender-specific epilepsies such as catamenial epilepsy, a neuroendocrine condition in which seizures are most often clustered around the perimenstrual or periovulatory period in adult women. Structural differences in cerebral morphology, the structural and functional circuits may render men and women differentially vulnerable to seizure disorders and epileptogenic processes. Changes in seizure sensitivity are evident at puberty, pregnancy, and menopause, often attributed to circulating steroid hormones and neurosteroids as well as neuroplasticity in receptor systems. An improved understanding of the sexual dimorphism in neural circuits and the neuroendocrine basis of sex differences or resistance to protective drugs is essential to develop sex-specific therapies for seizure conditions.

Sex Differences in the Epilepsies and Associated Comorbidities: Implications for Use and Development of Pharmacotherapies

The epilepsies are common neurologic disorders characterized by spontaneous recurrent seizures. Boys, girls, men, and women of all ages are affected by epilepsy and, in many cases, by associated comorbidities as well. The primary courses of treatment are pharmacological, dietary, and/or surgical, depending on several factors, including the areas of the brain affected and the severity of the epilepsy. There is a growing appreciation that sex differences in underlying brain function and in the neurobiology of epilepsy are important factors that should be accounted for in the design and development of new therapies. In this review, we discuss the current knowledge on sex differences in epilepsy and associated comorbidities, with emphasis on those aspects most informative for the development of new pharmacotherapies. Particular focus is placed on sex differences in the prevalence and presentation of various focal and generalized epilepsies; psychiatric, cognitive, and physiologic comorbidities; catamenial epilepsy in women; sex differences in brain development; the neural actions of sex and stress hormones and their metabolites; and cellular mechanisms, including brain-derived neurotrophic factor signaling and neuronal-glial interactions. Further attention placed on potential sex differences in epilepsies, comorbidities, and drug effects will enhance therapeutic options and efficacy for all patients with epilepsy. SIGNIFICANCE STATEMENT: Epilepsy is a common neurological disorder that often presents together with various comorbidities. The features of epilepsy and seizure activity as well as comorbid afflictions can vary between men and women. In this review, we discuss sex differences in types of epilepsies, associated comorbidities, pathophysiological mechanisms, and antiepileptic drug efficacy in both clinical patient populations and preclinical animal models.

Dynamics of androgens in healthy and hospitalized newborn foals

Background

Information on steroids derived from the adrenal glands, gonads, or fetoplacental unit is minimal in newborn foals.

Objective

To measure androgen concentrations in serum and determine their association with disease severity and outcome in hospitalized foals.

Animals

Hospitalized (n = 145) and healthy (n = 80) foals.

Methods

Prospective, multicenter, cross‐sectional study. Foals of ≤3 days of age from 3 hospitals and horse farms were classified as healthy and hospitalized (septic, sick nonseptic, neonatal maladjustment syndrome [NMS]) based on physical exam, medical history, and laboratory findings. Serum androgen and plasma ACTH concentrations were measured with immunoassays. Data were analyzed by nonparametric methods and univariate analysis.

Results

Serum dehydroepiandrosterone (DHEA), androstenedione, testosterone, and dihydrotestosterone (DHT) concentrations were higher upon admission in hospitalized foals (P <  .05), were associated with nonsurvival, decreased to 4.9‐10.8%, 5.7‐31%, and 30.8‐62.8% admission values in healthy, SNS, and septic foals, respectively (P < .05), but remained unchanged or increased in nonsurviving foals. ACTH:androgen ratios were higher in septic and NMS foals (P < .05). Foals with decreased androgen clearance were more likely to die (odds ratio > 3; P < .05).

Conclusions and Clinical Importance

Similar to glucocorticoids, mineralocorticoids, and progestagens, increased serum concentrations of androgens are associated with disease severity and adverse outcome in hospitalized newborn foals. In healthy foals, androgens decrease over time, however, remain elevated longer in septic and nonsurviving foals. Androgens could play a role in or reflect a response to disorders such as sepsis or NMS in newborn foals.

Interactions of Aromatase and Seladin-1: A Neurosteroidogenic and Gender Perspective

Aromatase and seladin-1 are enzymes that have major roles in estrogen synthesis and are important in both brain physiology and pathology. Aromatase is the key enzyme that catalyzes estrogen biosynthesis from androgen precursors and regulates the brain’s neurosteroidogenic activity. Seladin-1 is the enzyme that catalyzes the last step in the biosynthesis of cholesterol, the precursor of all hormones, from desmosterol. Studies indicated that seladin-1 is a downstream mediator of the neuroprotective activity of estrogen. Recently, we also showed that there is an interaction between aromatase and seladin-1 in the brain. Therefore, the expression of local brain aromatase and seladin-1 is important, as they produce neuroactive steroids in the brain for the protection of neuronal damage. Increasing steroid biosynthesis specifically in the central nervous system (CNS) without affecting peripheral hormone levels may be possible by manipulating brain-specific promoters of steroidogenic enzymes. This review emphasizes that local estrogen, rather than plasma estrogen, may be responsible for estrogens’ protective effects in the brain. Therefore, the roles of aromatase and seladin-1 and their interactions in neurodegenerative events such as Alzheimer’s disease (AD), ischemia/reperfusion injury (stroke), and epilepsy are also discussed in this review.

Design and development of letrozole nanoemulsion: A comparative evaluation of brain targeted nanoemulsion with free letrozole against status epilepticus and neurodegeneration in mice

The target of the current study is to formulate letrozole loaded nanoemulsion (LET-NE) for the direct nose to brain delivery to reduce peripheral effects of letrozole (LET). LET-NE is compared against intraperitoneally administered free LET in kainic acid (KA) induced status epilepticus (SE) in mice. LET loaded nanoemulsion (LET-NE) was prepared by aqueous microtitration method using Triacetin, Tween 80 and PEG-400 as the oil phase, surfactant, and co-surfactant. Nanoemulsion was studied for droplet size, polydispersity index (PDI), zeta potential, percentage transmittance, drug content, surface morphology. TEM images of developed formulation demonstrated spherical droplets with a mean diameter of 95.59 ± 2.34 nm, PDI of 0.162 ± 0.012 and zeta potential of -7.12 ± 0.12 mV respectively. In in-vitro and ex-vivo drug release, LET-NE showed prolonged drug release profile as compared to suspension. SE was induced by KA (10 mg/kg, i.p.) in Swiss albino mice. Behavioral seizure monitoring, biochemical estimations, and histopathological examination were performed. The onset time of SE was significantly enhanced and % incidence of SE was reduced by intranasal administration of LET-NE as compared to KA and LET administered intraperitoneally. Biochemical estimations revealed that LET-NE effectively decreased levels of 17-β estradiol while the levels of 5α-Dihydrotestosterone (5α-DHT) and 3α-androstanediol (3α-Diol) were significantly increased in the hippocampus. In cresyl violet staining LET-NE showed better protection of the hippocampus from neurotoxicity induced by KA as compared to LET. Also, in gamma scintigraphy of mouse brain, intranasal administration of nanoemulsion exhibited the presence of high concentration of LET. The study demonstrates the anticonvulsant and neuroprotective effect of LET-NE probably by inhibition of aromatization of testosterone into 17-β estradiol, proconvulsant, and diverting the pathway into the synthesis of testosterone metabolites, 3α-Diol with known anticonvulsant and neuroprotective action. Brain targeting of LET-NE showed better anticonvulsant and neuroprotective action than LET.

Extrasynaptic γ-aminobutyric acid type A receptor-mediated sex differences in the antiseizure activity of neurosteroids in status epilepticus and complex partial seizures

OBJECTIVE

Sex differences are evident in the antiseizure activity of neurosteroids; however, the potential mechanisms remain unclear. In this study, we sought to determine whether differences in target extrasynaptic δ-subunit γ-aminobutyric acid type A (GABA-A) receptor expression and function underlie the sex differences in seizure susceptibility and the antiseizure activity of neurosteroids.

METHODS

Sex differences in seizure susceptibility and protective activity of three distinct neurosteroids-allopregnanolone (AP), androstanediol (AD), and ganaxolone-were evaluated in the pilocarpine model of status epilepticus (SE) and kindling seizure test in mice. Immunocytochemistry was used for δGABA-A receptor expression analysis, and patch-clamp recordings in brain slices evaluated its functional currents.

RESULTS

Sex differences were apparent in kindling epileptogenic seizures, with males exhibiting a faster progression to a fully kindled state. Neurosteroids AP, AD, or ganaxolone produced dose-dependent protection against SE and acute partial seizures. However, female mice exhibited strikingly enhanced sensitivity to the antiseizure activity of neurosteroids compared to males. Sex differences in neurosteroid protection were unrelated to pharmacokinetic factors, as plasma levels of neurosteroids associated with seizure protection were similar between sexes. Mice lacking extrasynaptic δGABA-A receptors did not exhibit sex differences in neurosteroid protection. Consistent with a greater abundance of extrasynaptic δGABA-A receptors, AP produced a significantly greater potentiation of tonic currents in dentate gyrus granule cells in females than males; however, such enhanced AP sensitivity was diminished in δGABA-A receptor knockout female mice.

SIGNIFICANCE

Neurosteroids exhibit greater antiseizure potency in females than males, likely due to a greater abundance of extrasynaptic δGABA-A receptors that mediate neurosteroid-sensitive tonic currents and seizure protection. These findings indicate the potential to develop personalized gender-specific neurosteroid treatments for SE and epilepsy in men and women, including catamenial epilepsy.

Effects of androsterone on the protective action of various antiepileptic drugs against maximal electroshock-induced seizures in mice

This study evaluated the effect of androsterone (AND), a metabolite of testosterone, on the ability of selected classical and novel antiepileptic drugs to prevent seizures caused by maximal electroshock (MES), which may serve as an experimental model of human generalized tonic-clonic seizures in mice. Single intraperitoneal (i.p.) administration of AND (80 mg kg^-1) significantly raised the threshold for convulsions in the MES seizure threshold test. Lower doses of AND (5, 10, 20, and 40 mg kg^-1) failed to change the threshold. AND at a subthreshold dose of 40 mg kg^-1 significantly enhanced the protective activity of carbamazepine, gabapentin, and phenobarbital against MES-induced seizures decreasing their median effective doses (ED₅₀) values ± SEM from 8.59 ± 0.76 to 6.05 ± 0.81 mg kg^-1 (p = 0.0308) for carbamazepine, from 419.9 ± 120.6 to 111.5 ± 41.1 mg kg^-1 (p = 0.0405) for gabapentin, and from 20.86 ± 1.64 to 10.0 ± 1.21 mg kg^-1 (p = 0.0007) for phenobarbital. There were no significant changes in total brain concentrations of carbamazepine, gabapentin, and phenobarbital following AND administration. This suggests that the enhancing effects of AND on the protective activity of these antiepileptic drugs are not related to pharmacokinetic factors. A lower dose of AND (20 mg kg^-1) had no effect on the protective activity of carbamazepine, gabapentin, and phenobarbital. AND administered at a dose of 40 mg kg^-1 failed to change the anticonvulsant activity of lamotrigine, oxcarbazepine, phenytoin, topiramate, and valproate in the MES test. In the chimney test, AND given at a dose enhancing the protective activity of carbamazepine, gabapentin, and phenobarbital (which alone was without effect on motor performance of mice) did not affect impairment of motor coordination produced by the antiepileptics. Our findings recommend further preclinical and clinical research on AND in respect of its use as adjuvant therapy in the management of epilepsy in men with deficiency of androgens.

Common data elements (CDEs) for preclinical epilepsy research: Introduction to CDEs and description of core CDEs. A TASK3 report of the ILAE/AES joint translational task force

Common data elements (CDEs) are becoming more common as more areas of preclinical research have generated CDEs. Herein we provide an overview of the progress to date in generating CDEs for preclinical epilepsy research. Currently there are CDEs that have been developed for Physiology (in vivo), Behavior, Pharmacology, and Electroencephalography (EEG). Together the CDEs and methodologic considerations associated with these CDEs are laid out in consecutive manuscripts published in Epilepsia Open, each describing CDEs for their respective topic area. In addition to the overview of progress for the 4 subjects, core characteristics (Core CDEs) are described and explained. Data collection using a case report form (CRF) is described, and considerations that are involved in using the CDEs and CRFs are discussed.

Chronic levetiracetam decreases hippocampal and testicular aromatase expression in normal but not kainic acid-induced experimental model of acute seizures in rats

Reproductive disorders are more common in men with epilepsy taking anticonvulsant medications. Antiseizure/anticonvulsant drugs and seizures in medial temporal lobe structures may cause gonadal dysfunction, including infertility, decreased libido, and potency. Levels of circulating bioavailable testosterone are affected by the aromatase enzyme, which converts testosterone into estrogen and may be affected by seizure medications. However, the relationship of anticonvulsant drugs with central aromatase levels is not clear. This study investigated the possible effects of the highly efficient, new-generation antiseizure/anticonvulsant drug levetiracetam on central and gonadal aromatase expression and gonadal tissue functionality at 27 and 54 mg/kg/day doses. Epileptogenesis was generated in male Wistar rats by an intraperitoneal injection of the excitotoxic agent kainic acid. Aromatase levels were 1.5 times higher in the brain cortex of the kainic acid groups after 4 weeks and the hippocampus after 4 and 8 weeks compared with the controls. Decreased basal aromatase levels were observed after 1 week of levetiracetam treatment (27 mg/kg/day). Administration of 27 mg/kg/day levetiracetam did not alter vas deferens contractions at 1, 4, or 8 weeks compared with the controls. No histological changes were observed in the vas deferens, epididymis, or testis after 8 weeks of levetiracetam administration at both doses. Administration of 27 and 54 mg/kg/day levetiracetam downregulated testis aromatase expression at 8 weeks compared with the controls. These results suggest that levetiracetam decreases aromatase levels in the testis and increases the seizure threshold by a possible decrease in systemic estradiol levels.

Neuroactive Steroids and Affective Symptoms in Women Across the Weight Spectrum

3α-5α-Tetrahydroprogesterone, a progesterone metabolite also known as allopregnanolone, and 5α-androstane-3α,17β-diol, a testosterone metabolite also known as 3α-androstanediol, are neuroactive steroids and positive GABA_A receptor allosteric modulators. Both anorexia nervosa (AN) and obesity are complicated by affective comorbidities and hypothalamic-pituitary-gonadal dysregulation. However, it is not known whether neuroactive steroid levels are abnormal at the extremes of the weight spectrum. We hypothesized that serum allopregnanolone and 3α-androstanediol levels would be decreased in AN compared with healthy controls (HC) and negatively associated with affective symptoms throughout the weight spectrum, independent of body mass index (BMI). Thirty-six women were 1 : 1 age-matched across three groups: AN, HC, and overweight/obese (OW/OB). AN were amenorrheic; HC and OW/OB were studied in the follicular phase. Fasting serum neuroactive steroids were measured by gas chromatography/mass spectrometry. Mean Hamilton depression and anxiety scores were highest in AN (p<0.0001). Mean serum allopregnanolone was lower in AN and OW/OB than HC (AN 95.3±56.4 vs OW/OB 73.8±31.3 vs HC 199.5±167.8 pg/ml, p=0.01), despite comparable mean serum progesterone. Allopregnanolone levels, but not progesterone levels, were negatively associated with depression and anxiety symptom severity, independent of BMI. Serum 3α-androstanediol levels did not differ among groups and were not associated with depression or anxiety scores, despite a significant negative association between free testosterone levels and both anxiety and depression severity. In conclusion, women at both extremes of the weight spectrum have low mean serum allopregnanolone, which is associated with increased depression and anxiety severity, independent of BMI. Neuroactive steroids such as allopregnanolone may be potential therapeutic targets for depression and anxiety in traditionally treatment-resistant groups, including AN.

GABA-A Receptors Mediate Tonic Inhibition and Neurosteroid Sensitivity in the Brain

Neurosteroids like allopregnanolone (AP) are positive allosteric modulators of synaptic and extrasynaptic GABA-A receptors. AP and related neurosteroids exhibit a greater potency for δ-containing extrasynaptic receptors. The δGABA-A receptors, which are expressed extrasynaptically in the dentate gyrus and other regions, contribute to tonic inhibition, promoting network shunting as well as reducing seizure susceptibility. Levels of endogenous neurosteroids fluctuate with ovarian cycle. Natural and synthetic neurosteroids maximally potentiate tonic inhibition in the hippocampus and provide robust protection against a variety of limbic seizures and status epilepticus. Recently, a consensus neurosteroid pharmacophore model has been proposed at extrasynaptic δGABA-A receptors based on structure-activity relationship for functional activation of tonic currents and seizure protection. Aside from anticonvulsant actions, neurosteroids have been found to be powerful anxiolytic and anesthetic agents. Neurosteroids and Zn²⁺ have preferential affinity for δ-containing receptors. Thus, Zn²⁺ can prevent neurosteroid activation of extrasynaptic δGABA-A receptor-mediated tonic inhibition. Recently, we demonstrated that Zn²⁺ selectively inhibits extrasynaptic δGABA-A receptors and thereby fully prevents AP activation of tonic inhibition and seizure protection. We confirmed that neurosteroids exhibit greater sensitivity at extrasynaptic δGABA-A receptors. Overall, extrasynaptic GABA-A receptors are primary mediators of tonic inhibition in the brain and play a key role in the pathophysiology of epilepsy and other neurological disorders.

Sex differences in the anticonvulsant activity of neurosteroids

Epilepsy is one of the leading causes of chronic neurological morbidity worldwide. Acquired epilepsy may result from a number of conditions, such as brain injury, anoxia, tumors, stroke, neurotoxicity, and prolonged seizures. Sex differences have been observed in many seizure types; however, some sex-specific seizure disorders are much more prevalent in women. Despite some inconsistencies, substantial data indicates that sensitivity to seizure stimuli differs between the sexes. Men generally exhibit greater seizure susceptibility than women, whereas many women with epilepsy experience a cyclical occurrence of seizures that tends to center around the menstrual period, which has been termed catamenial epilepsy. Some epilepsy syndromes show gender differences with female predominance or male predominance. Steroid hormones, endogenous neurosteroids, and sexually dimorphic neural networks appear to play a key role in sex differences in seizure susceptibility. Neurosteroids, such as allopregnanolone, reflect sex differences in their anticonvulsant activity. This Review provides a brief overview of the evidence for sex differences in epilepsy and how sex differences influence the use of neurosteroids in epilepsy and epileptogenesis. © 2016 Wiley Periodicals, Inc.

Brief activation of GABAergic interneurons initiates the transition to ictal events through post-inhibitory rebound excitation

Activation of γ-aminobutyric acid (GABA_A) receptors have been associated with the onset of epileptiform events. To investigate if a causal relationship exists between GABA_A receptor activation and ictal event onset, we activated inhibitory GABAergic networks in the superficial layer (2/3) of the somatosensory cortex during hyperexcitable conditions using optogenetic techniques in mice expressing channelrhodopsin-2 in all GABAergic interneurons. We found that a brief 30ms light pulse reliably triggered either an interictal-like event (IIE) or ictal-like ("ictal") event in the in vitro cortical 4-Aminopyridine (4-AP) slice model. The link between light pulse and epileptiform event onset was lost following blockade of GABA_A receptors with bicuculline methiodide. Additionally, recording the chronological sequence of events following a light pulse in a variety of configurations (whole-cell, gramicidin-perforated patch, and multi-electrode array) demonstrated an initial hyperpolarization followed by post-inhibitory rebound spiking and a subsequent slow depolarization at the transition to epileptiform activity. Furthermore, the light-triggered ictal events were independent of the duration or intensity of the initiating light pulse, suggesting an underlying regenerative mechanism. Moreover, we demonstrated that brief GABA_A receptor activation can initiate ictal events in the in vivo 4-AP mouse model, in another common in vitro model of epileptiform activity, and in neocortical tissue resected from epilepsy patients. Our findings reveal that the synchronous activation of GABAergic interneurons is a robust trigger for ictal event onset in hyperexcitable cortical networks.

Novel therapeutic approaches for disease-modification of epileptogenesis for curing epilepsy

This article describes the recent advances in epileptogenesis and novel therapeutic approaches for the prevention of epilepsy, with a special emphasis on the pharmacological basis of disease-modification of epileptogenesis for curing epilepsy. Here we assess animal studies and human clinical trials of epilepsy spanning 1982-2016. Epilepsy arises from a number of neuronal factors that trigger epileptogenesis, which is the process by which a brain shifts from a normal physiologic state to an epileptic condition. The events precipitating these changes can be of diverse origin, including traumatic brain injury, cerebrovascular damage, infections, chemical neurotoxicity, and emergency seizure conditions such as status epilepticus. Expectedly, the molecular and system mechanisms responsible for epileptogenesis are not well defined or understood. To date, there is no approved therapy for the prevention of epilepsy. Epigenetic dysregulation, neuroinflammation, and neurodegeneration appear to trigger epileptogenesis. Targeted drugs are being identified that can truly prevent the development of epilepsy in at-risk people. The promising agents include rapamycin, COX-2 inhibitors, TRK inhibitors, epigenetic modulators, JAK-STAT inhibitors, and neurosteroids. Recent evidence suggests that neurosteroids may play a role in modulating epileptogenesis. A number of promising drugs are under investigation for the prevention or modification of epileptogenesis to halt the development of epilepsy. Some drugs in development appear rational for preventing epilepsy because they target the initial trigger or related signaling pathways as the brain becomes progressively more prone to seizures. Additional research into the target validity and clinical investigation is essential to make new frontiers in curing epilepsy.

Expansion of mossy fibers and CA3 apical dendritic length accompanies the fall in dendritic spine density after gonadectomy in male, but not female, rats

Androgen loss is an important clinical concern because of its cognitive and behavioral effects. Changes in androgen levels are also suspected to contribute to neurological disease. However, the available data on the effects of androgen deprivation in areas of the brain that are central to cognition, like the hippocampus, are mixed. In this study, morphological analysis of pyramidal cells was used to investigate if structural changes could potentially contribute to the mixed cognitive effects that have been observed after androgen loss in males. Male Sprague-Dawley rats were orchidectomized or sham-operated. Two months later, their brains were Golgi-impregnated for morphological analysis. Morphological endpoints were studied in areas CA3 and CA1, with comparisons to females either intact or 2 months after ovariectomy. CA3 pyramidal neurons of orchidectomized rats exhibited marked increases in apical dendritic arborization. There were increases in mossy fiber afferent density in area CA3, as well as robust enhancements to dendritic structure in area CA3 of orchidectomized males, but not in CA1. Remarkably, apical dendritic length of CA3 pyramidal cells increased, while spine density declined. By contrast, in females overall dendritic structure was minimally affected by ovariectomy, while dendritic spine density was greatly reduced. Sex differences and subfield-specific effects of gonadal hormone deprivation on the hippocampal circuitry may help explain the different behavioral effects reported in males and females after gonadectomy, or other conditions associated with declining gonadal hormone secretion.

Sex-Dependent Regulation of Aromatase-Mediated Synaptic Plasticity in the Basolateral Amygdala

The basolateral amygdala (BLA) integrates sensory input from cortical and subcortical regions, a function that requires marked synaptic plasticity. Here we provide evidence that cytochrome P450 aromatase (AROM), the enzyme converting testosterone to 17β-estradiol (E2), contributes to the regulation of this plasticity in a sex-specific manner. We show that AROM is expressed in the BLA, particularly in the basolateral nucleus (BL), in male and female rodents. Systemic administration of the AROM inhibitor letrozole reduced spine synapse density in the BL of adult female mice but not in the BL of male mice. Similarly, in organotypic corticoamygdalar slice cultures from immature rats, treatment with letrozole significantly reduced spine synapses in the BL only in cultures derived from females. In addition, letrozole sex-specifically altered synaptic properties in the BL: in acute slices from juvenile (prepubertal) female rats, wash-in of letrozole virtually abolished long-term potentiation (LTP), whereas it did not prevent the generation of LTP in the slices from males. Together, these data indicate that neuron-derived E2 modulates synaptic plasticity in rodent BLA sex-dependently. As protein expression levels of AROM, estrogen and androgen receptors did not differ between males and females and were not sex-specifically altered by letrozole, the findings suggest sex-specific mechanisms of E2 signaling.SIGNIFICANCE STATEMENT The basolateral amygdala (BLA) is a key structure of the fear circuit. This research reveals a sexually dimorphic regulation of synaptic plasticity in the BLA involving neuronal aromatase, which produces the neurosteroid 17β-estradiol (E2). As male and female neurons in rodent BLA responded differently to aromatase inhibition both in vivo and in vitro, our findings suggest that E2 signaling in BLA neurons is regulated sex-dependently, presumably via mechanisms that have been established during sexual determination. These findings could be relevant for the understanding of sex differences in mood disorders and of the side effects of cytochrome P450 aromatase inhibitors, which are frequently used for breast cancer therapy.

Do oral contraceptives increase epileptic seizures?

INTRODUCTION

Hormonal contraceptives are used by over 100 million people worldwide. Recently, there has been an emerging interest in studying the potential impact of oral contraceptives (OCs) on certain neurological conditions. It has been suspected for some time that hormonal birth control increases seizure activity in women with epilepsy, but there is little supportive data. Areas covered: Literature from PubMed and online sources was analyzed with respect to hormonal contraception and epilepsy or seizures. New evidence indicates that OCs can cause an increase in seizures in women with epilepsy. The epilepsy birth control registry, which surveyed women with epilepsy, found that those using hormonal contraceptives self-reported 4.5 times more seizures than those that did not use such contraceptives. A preclinical study confirmed these outcomes wherein epileptic animals given ethinyl estradiol, the primary component of OCs, had more frequent seizures that are more likely to be resistant. Expert commentary: OC pills may increase seizures in women with epilepsy and such refractory seizures are more likely to cause neuronal damage in the brain. Thus, women of child bearing age with epilepsy should consider using non-hormonal forms of birth control to avoid risks from OC pills. Additional research into the mechanisms and prospective clinical investigation are needed.

The neuroendocrine basis of sex differences in epilepsy

Epilepsy affects people of all ages and both genders. Sex differences are well known in epilepsy. Seizure susceptibility and the incidence of epilepsy are generally higher in men than women. In addition, there are gender-specific epilepsies such as catamenial epilepsy, a neuroendocrine condition in which seizures are most often clustered around the perimenstrual or periovulatory period in adult women with epilepsy. Changes in seizure sensitivity are also evident at puberty, pregnancy, and menopause. Sex differences in seizure susceptibility and resistance to antiseizure drugs can be studied in experimental models. An improved understanding of the neuroendocrine basis of sex differences or resistance to protective drugs is essential to develop targeted therapies for sex-specific seizure conditions. This article provides a brief overview of the current status of sex differences in seizure susceptibility and the potential mechanisms underlying the gender differences in seizure sensitivity.

Clinical Potential of Neurosteroids for CNS Disorders

Neurosteroids are key endogenous molecules in the brain that affect many neural functions. We describe here recent advances in US National Institutes of Health (NIH)-sponsored and other clinical studies of neurosteroids for CNS disorders. The neuronal GABA-A receptor chloride channel is one of the prime molecular targets of neurosteroids. Allopregnanolone-like neurosteroids are potent allosteric agonists as well as direct activators of both synaptic and extrasynaptic GABA-A receptors. Hence, neurosteroids can maximally enhance synaptic phasic and extrasynaptic tonic inhibition. The resulting chloride current conductance generates a form of shunting inhibition that controls network excitability, seizures, and behavior. Such mechanisms of neurosteroids are providing innovative therapies for epilepsy, status epilepticus (SE), traumatic brain injury (TBI), fragile X syndrome (FXS), and chemical neurotoxicity. The neurosteroid field has entered a new era, and many compounds have reached advanced clinical trials. Synthetic analogs have several advantages over natural neurosteroids for clinical use because of their superior bioavailability and safety trends.

Catamenial Epilepsy: Discovery of an Extrasynaptic Molecular Mechanism for Targeted Therapy

Catamenial epilepsy is a type of refractory epilepsy characterized by seizure clusters around perimenstrual or periovulatory period. The pathophysiology of catamenial epilepsy still remains unclear, yet there are few animal models to study this gender-specific disorder. The pathophysiology of perimenstrual catamenial epilepsy involves the withdrawal of the progesterone-derived GABAergic neurosteroids due to the decline in progesterone level at the time of menstruation. These manifestations can be faithfully reproduced in rodents by specific neuroendocrine manipulations. Since mice and rats, like humans, have ovarian cycles with circulating hormones, they appear to be suitable animal models for studies of perimenstrual seizures. Recently, we created specific experimental models to mimic perimenstrual seizures. Studies in rat and mouse models of catamenial epilepsy show enhanced susceptibility to seizures or increased seizure exacerbations following neurosteroid withdrawal. During such a seizure exacerbation period, there is a striking decrease in the anticonvulsant effect of commonly prescribed antiepileptics, such as benzodiazepines, but an increase in the anticonvulsant potency of exogenous neurosteroids. We discovered an extrasynaptic molecular mechanism of catamenial epilepsy. In essence, extrasynaptic δGABA-A receptors are upregulated during perimenstrual-like neuroendocrine milieu. Consequently, there is enhanced antiseizure efficacy of neurosteroids in catamenial models because δGABA-A receptors confer neurosteroid sensitivity and greater seizure protection. Molecular mechanisms such as these offer a strong rationale for the clinical development of a neurosteroid replacement therapy for catamenial epilepsy.

Neurosteroid Structure-Activity Relationships for Functional Activation of Extrasynaptic δGABA(A) Receptors

Synaptic GABAA receptors are primary mediators of rapid inhibition in the brain and play a key role in the pathophysiology of epilepsy and other neurologic disorders. The δ-subunit GABAA receptors are expressed extrasynaptically in the dentate gyrus and contribute to tonic inhibition, promoting network shunting as well as reducing seizure susceptibility. However, the neurosteroid structure-function relationship at δGABA(A) receptors within the native hippocampus neurons remains unclear. Here we report a structure-activity relationship for neurosteroid modulation of extrasynaptic GABAA receptor-mediated tonic inhibition in the murine dentate gyrus granule cells. We recorded neurosteroid allosteric potentiation of GABA as well as direct activation of tonic currents using a wide array of natural and synthetic neurosteroids. Our results shows that, for all neurosteroids, the C3α-OH group remains obligatory for extrasynaptic receptor functional activity, as C3β-OH epimers were inactive in activating tonic currents. Allopregnanolone and related pregnane analogs exhibited the highest potency and maximal efficacy in promoting tonic currents. Alterations at the C17 or C20 region of the neurosteroid molecule drastically altered the transduction kinetics of tonic current activation. The androstane analogs had the weakest modulatory response among the analogs tested. Neurosteroid potentiation of tonic currents was completely (approximately 95%) diminished in granule cells from δ-knockout mice, suggesting that δ-subunit receptors are essential for neurosteroid activity. The neurosteroid sensitivity of δGABA(A) receptors was confirmed at the systems level using a 6-Hz seizure test. A consensus neurosteroid pharmacophore model at extrasynaptic δGABA(A) receptors is proposed based on a structure-activity relationship for activation of tonic current and seizure protection.

Seizure facilitating activity of the oral contraceptive ethinyl estradiol

Contraceptive management is critical in women with epilepsy. Although oral contraceptives (OCs) are widely used by many women with epilepsy, little is known about their impact on epileptic seizures and epileptogenesis. Ethinyl estradiol (EE) is the primary component of OC pills. In this study, we investigated the pharmacological effect of EE on epileptogenesis and kindled seizures in female mice using the hippocampus kindling model. Animals were stimulated daily with or without EE until generalized stage 5 seizures were elicited. EE treatment significantly accelerated the rate of epileptogenesis. In acute studies, EE caused a significant decrease in the afterdischarge threshold and increased the incidence and severity of seizures in fully-kindled mice. In chronic studies, EE treatment caused a greater susceptibility to kindled seizures. Collectively, these results are consistent with moderate proconvulsant-like activity of EE. Such excitatory effects may affect seizure risk in women with epilepsy taking OC pills.

Ontogenetic Change in the Regional Distribution of Dehydroepiandrosterone-Synthesizing Enzyme and the Glucocorticoid Receptor in the Brain of the Spiny Mouse (Acomys cahirinus)

The androgen dehydroepiandrosterone (DHEA) has trophic and anti-glucocorticoid actions on brain growth. The adrenal gland of the spiny mouse (Acomys cahirinus) synthesizes DHEA. The aim of this study was to determine whether the brain of this precocial species is also able to produce DHEA de novo during fetal, neonatal and adult life. The expression of P450c17 and cytochrome b5 (Cytb5), the enzyme and accessory protein responsible for the synthesis of DHEA, was determined in fetal, neonatal and adult brains by immunocytochemistry, and P450c17 bioactivity was determined by the conversion of pregnenolone to DHEA. Homogenates of fetal brain produced significantly more DHEA after 48 h in culture (22.46 ± 2.0 ng/mg tissue) than adult brain homogenates (5.04 ± 2.0 ng/mg tissue; p < 0.0001). P450c17 and Cytb5 were co-expressed in fetal neurons but predominantly in oligodendrocytes and white matter tracts in the adult brain. Because DHEA modulates glucocorticoids actions, the expression of the glucocorticoid receptor (GR) was also determined. In the brainstem, medulla, midbrain, and cerebellum, the predominant GR localization changed from neurons in the fetal brain to oligodendrocytes and white matter tracts in the adult brain. The change of expression of P450c17, Cytb5 and GR proteins with cell type, brain region and developmental age indicates that DHEA is an endogenous neurosteroid in this species that may have important trophic and stress-modifying actions during both prenatal and postnatal life.

Reduced estradiol synthesis by letrozole, an aromatase inhibitor, is protective against development of pentylenetetrazole-induced kindling in mice

Neurosteroids, such as testosterone and their metabolites, are known to modulate neuronal excitability. The enzymes regulating the metabolism of these neurosteroids, thus, may be targeted as a noval strategy for the development of new antiepileptic drugs. The present work targeted two such enzymes i,e aromatase and 5α-reductase in order to explore the potential of letrozole (an aromatase inhibitor) on pentylenetetrazole (PTZ)-induced kindling in mice and the ability of finasteride (a 5α-reductase inhibitor) to modulate any such effects. PTZ (30 mg/kg, i.p.), when administered once every two days (for a total of 24 doses) induced kindling in Swiss albino mice. Letrozole (1 mg/kg, p.o.), administered prior to PTZ, significantly reduced the % incidence of kindling, delayed mean onset time of seizures and reduced seizure severity score. Letrozole reduced the levels of plasma 17β-estradiol after induction of kindling. The concurrent administration of finasteride and letrozole produced effects similar to letrozole on PTZ-kindling and on estradiol levels. This implies that the ability of letrozole to redirect the synthesis of dihydrotestosterone (DHT) and 5α-androstanediol from testosterone doesn't appear to play a significant role in the protective effects of letrozole against PTZ kindling. Letrozole, however, increased the levels of 5α-DHT in mice plasma. The aromatase inhibitors, thus, may be exploited for inhibiting the synthesis of proconvulsant (17β-estradiol) and/or redirecting the synthesis of anticonvulsant (DHT and 5α-androstanediol) neurosteroids.

Treatment of hypopituitarism in patients receiving antiepileptic drugs

Evidence suggests that there may be drug interactions between antiepileptic drugs and hormonal therapies, which can present a challenge to endocrinologists dealing with patients who have both hypopituitarism and neurological diseases. Data are scarce for this subgroup of patients; however, data for the interaction of antiepileptic drugs with the pituitary axis have shown that chronic use of many antiepileptic drugs, such as carbamazepine, oxcarbazepine, and topiramate, enhances hepatic cytochrome P450 3A4 (CYP3A4) activity, and can decrease serum concentrations of sex hormones. Other antiepileptic drugs increase sex hormone-binding globulin, which reduces the bioactivity of testosterone and estradiol. Additionally, the combined oestrogen-progestagen contraceptive pill might decrease lamotrigine concentrations, which could worsen seizure control. Moreover, sex hormones and their metabolites can directly act on neuronal excitability, acting as neurosteroids. Because carbamazepine and oxcarbazepine can enhance the sensitivity of renal tubules, a reduction in desmopressin dose might be necessary in patients with central diabetes insipidus. Although the effects of antiepileptic drugs in central hypothyroidism have not yet been studied, substantial evidence indicates that several antiepileptic drugs can increase thyroid hormone metabolism. However, although it is reasonable to expect a need for a thyroxine dose increase with some antiepileptic drugs, the effect of excessive thyroxine in lowering seizure threshold should also be considered. There are no reports of significant interactions between antiepileptic drugs and the efficacy of human growth hormone therapy, and few data are available for the effects of second-generation antiepileptic drugs on hypopituitarism treatment.

Dehydroepiandrosterone: a neuroactive steroid

Dehydroepiandrosterone (DHEA) and its sulfate bound form (DHEAS) are important steroids of mainly adrenal origin. They are produced also in gonads and in the brain. Dehydroepiandrosterone easily crosses the brain-blood barrier and in part is also produced locally in the brain tissue. In the brain, DHEA exerts its effects after conversion to either testosterone and dihydrotestosterone or estradiol via androgen and estrogen receptors present in the most parts of the human brain, through mainly non-genomic mechanisms, or eventually indirectly via the effects of its metabolites formed locally in the brain. As a neuroactive hormone, DHEA in co-operation with other hormones and transmitters significantly affects some aspects of human mood, and modifies some features of human emotions and behavior. It has been reported that its administration can increase feelings of well-being and is useful in ameliorating atypical depressive disorders. It has neuroprotective and antiglucocorticoid activity and modifies immune reactions, and some authors have also reported its role in degenerative brain diseases. Here we present a short overview of the possible actions of dehydroepiandrosterone and its sulfate in the brain, calling attention to various mechanisms of their action as neurosteroids and to prospects for the knowledge of their role in brain disorders.

Androgen Modulation of Hippocampal Structure and Function

Androgens have profound effects on hippocampal structure and function, including induction of spines and spine synapses on the dendrites of CA1 pyramidal neurons, as well as alterations in long-term synaptic plasticity (LTP) and hippocampally dependent cognitive behaviors. How these effects occur remains largely unknown. Emerging evidence, however, suggests that one of the key elements in the response mechanism may be modulation of brain-derived neurotrophic factor (BDNF) in the mossy fiber (MF) system. In male rats, orchidectomy increases synaptic transmission and excitability in the MF pathway. Testosterone reverses these effects, suggesting that testosterone exerts tonic suppression on MF BDNF levels. These findings suggest that changes in hippocampal function resulting from declining androgen levels may reflect the outcome of responses mediated through normally balanced, but opposing, mechanisms: loss of androgen effects on the hippocampal circuitry may be compensated, at least in part, by an increase in BDNF-dependent MF plasticity.

Risk factors for survival in a university hospital population of dogs with epilepsy

BACKGROUND

Although a common neurological disorder in dogs, long-term outcome of epilepsy is sparsely documented.

OBJECTIVES

To investigate risk factors for survival and duration of survival in a population of dogs with idiopathic epilepsy or epilepsy associated with a known intracranial cause.

ANIMALS

One hundred and two client owned dogs; 78 dogs with idiopathic epilepsy and 24 dogs with epilepsy associated with a known intracranial cause.

METHODS

A retrospective hospital based study with follow-up. Dogs diagnosed with epilepsy between 2002 and 2008 were enrolled in the study. Owners were interviewed by telephone using a structured questionnaire addressing epilepsy status, treatment, death/alive, and cause of death.

RESULTS

Median life span was 7.6 years, 9.2 years, and 5.8 years for all dogs, and dogs with idiopathic epilepsy or dogs with epilepsy associated with a known intracranial cause (P < .001), respectively. Survival time for dogs with idiopathic epilepsy was significantly (P = .0030) decreased for dogs euthanized because of epilepsy (median: 35 months) compared to dogs euthanized for other reasons (median: 67.5 months). Neutered male dogs with idiopathic epilepsy had a significant (P = .031) shorter survival (median: 38.5 months) after index seizure compared to intact male dogs (median: 71 months). Treatment with two antiepileptic drugs (AED's) did not negatively influence survival (P = .056).

CONCLUSION AND CLINICAL IMPORTANCE

Dogs with idiopathic epilepsy can in many cases expect a life span close to what is reported for dogs in general. In dogs where mono-therapy is not sufficient, the need for treatment with two AED's is not linked to a poor prognosis.

Dutasteride reduces alcohol's sedative effects in men in a human laboratory setting and reduces drinking in the natural environment

RATIONALE

Preclinical studies support the hypothesis that endogenous neuroactive steroids mediate some effects of alcohol.

OBJECTIVES

The aim of this study was to examine the effect of dutasteride inhibition of 5α-reduced neuroactive steroid production on subjective responses to alcohol in adult men.

METHODS

Using a within-subject factorial design, 70 men completed four randomly ordered monthly sessions in which pretreatment with 4 mg dutasteride or placebo was paired with a moderate dose of alcohol (0.8 g/kg) or placebo beverage. The pharmacologic effect of dutasteride was measured by an assay of serum androstanediol glucuronide. Self-reports of alcohol effects were obtained at 40-min intervals following alcohol administration using the Biphasic Alcohol Effects Scale (BAES) and the Alcohol Sensation Scale (SS). We used linear mixed models to examine the effects of dutasteride and alcohol on BAES and SS responses and the interaction of dutasteride with the GABRA2 alcohol dependence-associated polymorphism rs279858. We also examined whether exposure to dutasteride influenced drinking in the weeks following each laboratory session.

RESULTS

A single 4-mg dose of dutasteride produced a 70 % reduction in androstanediol glucuronide. Dutasteride pretreatment reduced alcohol effects on the BAES sedation and SS anesthesia scales. There was no interaction of dutasteride with rs279858. Heavy drinkers had fewer heavy drinking days during the 2 weeks following the dutasteride sessions and fewer total drinks in the first week after dutasteride.

CONCLUSIONS

These results provide evidence that neuroactive steroids mediate some of the sedative effects of alcohol in adult men and that dutasteride may reduce drinking, presumably through its effects on neuroactive steroid concentrations.

Animal models of absence epilepsies: what do they model and do sex and sex hormones matter?

While epidemiological data suggest a female prevalence in human childhood- and adolescence-onset typical absence epilepsy syndromes, the sex difference is less clear in adult-onset syndromes. In addition, although there are more females than males diagnosed with typical absence epilepsy syndromes, there is a paucity of studies on sex differences in seizure frequency and semiology in patients diagnosed with any absence epilepsy syndrome. Moreover, it is unknown if there are sex differences in the prevalence or expression of atypical absence epilepsy syndromes. Surprisingly, most studies of animal models of absence epilepsy either did not investigate sex differences, or failed to find sex-dependent effects. However, various rodent models for atypical syndromes such as the AY9944 model (prepubertal females show a higher incidence than prepubertal males), BN model (also with a higher prevalence in males) and the Gabra1 deletion mouse in the C57BL/6J strain offer unique possibilities for the investigation of the mechanisms involved in sex differences. Although the mechanistic bases for the sex differences in humans or these three models are not yet known, studies of the effects of sex hormones on seizures have offered some possibilities. The sex hormones progesterone, estradiol and testosterone exert diametrically opposite effects in genetic absence epilepsy and pharmacologically-evoked convulsive types of epilepsy models. In addition, acute pharmacological effects of progesterone on absence seizures during proestrus are opposite to those seen during pregnancy. 17β-Estradiol has anti-absence seizure effects, but it is only active in atypical absence models. It is speculated that the pro-absence action of progesterone, and perhaps also the delayed pro-absence action of testosterone, are mediated through the neurosteroid allopregnanolone and its structural and functional homolog, androstanediol. These two steroids increase extrasynaptic thalamic tonic GABAergic inhibition by selectively targeting neurosteroid-selective subunits of GABAA receptors (GABAARs). Neurosteroids also modulate the expression of GABAAR containing the γ2, α4, and δ subunits. It is hypothesized that differences in subunit expression during pregnancy and ovarian cycle contribute to the opposite effects of progesterone in these two hormonal states.

Neurosteroids and their role in sex-specific epilepsies

Neurosteroids are involved in sex-specific epilepsies. Allopregnanolone and related endogenous neurosteroids in the brain control excessive neuronal excitability and seizure susceptibility. Neurosteroids activate GABA-A receptors, especially extrasynaptic αγδ-GABA-A receptor subtypes that mediate tonic inhibition and thus dampen network excitability. Our studies over the past decade have shown that neurosteroids are broad-spectrum anticonvulsants and confer seizure protection in various animal models. Neurosteroids also exert antiepileptogenic effects. There is emerging evidence on a critical role for neurosteroids in the pathophysiology of the sex-specific forms of epilepsies such as catamenial epilepsy, a menstrual cycle-related seizure disorder in women. Catamenial epilepsy is a neuroendocrine condition in which seizures are clustered around specific points in the menstrual cycle, most often around the perimenstrual or periovulatory period. Apart from ovarian hormones, fluctuations in neurosteroid levels could play a critical role in this gender-specific epilepsy. Neurosteroids also regulate the plasticity of synaptic and extrasynaptic GABA-A receptors in the hippocampus and other regions involved in epilepsy pathology. Based on these studies, we proposed a neurosteroid replacement therapy for catamenial epilepsy. Thus, neurosteroids are novel drug targets for pharmacotherapy of epilepsy.

Female rats are more susceptible to central nervous system oxygen toxicity than male rats

Tonic–clonic seizures typify central nervous system oxygen toxicity (CNS‐OT) in humans and animals exposed to high levels of oxygen, as are encountered during scuba diving. We previously demonstrated that high doses of pseudoephedrine (PSE) decrease the latency to seizure (LS) for CNS‐OT in young male rats. This study investigated whether female rats respond similarly to PSE and hyperbaric oxygen (HBO). We implanted 60 virgin stock (VS) and 54 former breeder (FB) female rats with radio‐telemetry devices that measured brain electrical activity. One week later, rats were gavaged with saline or PSE in saline (40, 80, 120, 160, or 320 mg/kg) before diving to five atmospheres absolute in 100% oxygen. The time between reaching maximum pressure and exhibiting seizure was LS. Vaginal smears identified estrus cycle phase. PSE did not decrease LS for VS or FB, primarily because they exhibited low LS for all conditions tested. VS had shorter LS than males at 0, 40, and 80 mg/kg (−42, −49, and −57%, respectively). FB also had shorter LS than males at 0, 40, and 80 mg/kg (−60, −86, and −73%, respectively). FB were older than VS (286 ± 10 days vs. 128 ± 5 days) and weighed more than VS (299 ± 2.7 g vs. 272 ± 2.1 g). Males tested were younger (88 ± 2 days), heavier (340 ± 4.5 g), and gained more weight postoperatively (7.2 ± 1.6 g) than either VS (−0.4 ± 1.5 g) or FB (−1.6 ± 1.5 g); however, LS correlated poorly with age, body mass, change in body mass, and estrus cycle phase. We hypothesize that differences in sex hormones underlie females' higher susceptibility to CNS‐OT than males.

We previously reported that high doses of pseudoephedrine (PSE), a decongestant commonly used by scuba divers, decreases latency to seizure in a male rat model of central nervous system oxygen toxicity (CNS‐OT). We have now found that PSE does not have the same effect in female rats (either virgin stock [VS] or former breeders [FB]), primarily because female rats exhibit an inherently low latency to seizure. This sex difference appears to be independent of age, body mass, and estrus cycle phase.

Modulatory role of androgenic and estrogenic neurosteroids in determining the direction of synaptic plasticity in the CA1 hippocampal region of male rats

Estrogenic and androgenic neurosteroids can rapidly modulate synaptic plasticity in the brain through interaction with membrane receptors for estrogens (ERs) and androgens (ARs). We used electrophysiological recordings in slices of young and adolescent male rats to explore the influence of sex neurosteroids on synaptic plasticity in the CA1 hippocampal region, by blocking ARs or ERs during induction of long‐term depression (LTD) and depotentiation (DP) by low‐frequency stimulation (LFS) and long‐term potentiation (LTP) by high‐frequency stimulation (HFS). We found that LTD and DP depend on ARs, while LTP on ERs in both age groups. Accordingly, the AR blocker flutamide affected induction of LTD reverting it into LTP, and prevented DP, while having no effect on HFS‐dependent LTP. Conversely, ER blockade with ICI 182,780 (ICI) markedly reduced LTP, but did not influence LTD and DP. However, the receptor blockade did not affect the maintenance of either LTD or LTP. Moreover, we found that similar to LTP and LTD induced in control condition, the LTP unveiled by flutamide during LFS and residual LTP induced by HFS under ICI depended on N‐methyl‐d aspartate receptor (NMDAR) activation. Furthermore, as the synaptic paired‐pulse facilitation (PPF) was not affected by either AR or ER blockade, we suggest that sex neurosteroids act primarily at a postsynaptic level. This study demonstrates for the first time the crucial role of estrogenic and androgenic neurosteroids in determining the sign of hippocampal synaptic plasticity in male rat and the activity‐dependent recruitment of androgenic and estrogenic pathways leading to LTD and LTP, respectively.

This study shows a crucial and opposite role of estrogenic and androgenic neurosteroids in guiding the direction of synaptic plasticity in the hippocampus CA1 region of male rat, through activation of their specific receptors. In fact, by using selective antagonists for estrogen receptors (ICI 182,730) or androgen receptors (flutamide), we show that long‐term potentiation (LTP) induced by high‐frequency stimulation (HFS) depends on estrogenic signals, while long‐term depression (LTD) and depotentiation induced by low‐frequency stimulation (LFS) require activation of androgenic pathway. We suggest that different stimulation frequencies may lead to LTD or LTP depending on activation of specific neurosteroid pathway.