Androgenic neurosteroids: anti-seizure effects in an animal model of epilepsy

Androgens and Adult Neurogenesis in the Hippocampus

Adult neurogenesis in the hippocampus is modulated by steroid hormones, including androgens, in male rodents. In this review, we summarize research showing that chronic exposure to androgens, such as testosterone and dihydrotestosterone, enhances the survival of new neurons in the dentate gyrus of male, but not female, rodents, via the androgen receptor. However, the neurogenesis promoting the effect of androgens in the dentate gyrus may be limited to younger adulthood as it is not evident in middle-aged male rodents. Although direct exposure to androgens in adult or middle age does not significantly influence neurogenesis in female rodents, the aromatase inhibitor letrozole enhances neurogenesis in the hippocampus of middle-aged female mice. Unlike other androgens, androgenic anabolic steroids reduce neurogenesis in the hippocampus of male rodents. Collectively, the research indicates that the ability of androgens to enhance hippocampal neurogenesis in adult rodents is dependent on dose, androgen type, sex, duration, and age. We discuss these findings and how androgens may be influencing neuroprotection, via neurogenesis in the hippocampus, in the context of health and disease.

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.

Molecular mechanisms of sex differences in epilepsy and seizure susceptibility in chemical, genetic and acquired epileptogenesis

This article provides a succinct overview of sex differences in epilepsy and putative molecular mechanisms underlying sex differences in seizure susceptibility in chemical, genetic, and acquired epileptogenesis. The susceptibility to excitability episodes and occurrence of epileptic seizures are generally higher in men than women. The precise molecular mechanisms remain unclear, but differences in regional morphology and neural circuits in men and women may explain differential vulnerability to seizures and epileptogenic cascades. Changes in seizure sensitivity can be attributed to steroid hormones, including fluctuations in neurosteroids as well as neuroplasticity in their receptor signaling systems. Other potential neurobiological bases for sex differences in epilepsies include differences in brain development, neurogenesis, neuronal chloride homeostasis, and neurotrophic and glial responses. In catamenial epilepsy, a gender-specific neuroendocrine condition, epileptic seizures are most often clustered around a specific menstrual period in adult women. A deeper understanding of the molecular and neural network basis of sex differences in seizures and response to antiepileptic drugs is highly warranted for designing effective, sex-specific therapies for epilepsy, epileptogenesis, and seizure disorders.

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.

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.

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.

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.

Contribution of estradiol in sex-dependent differences of pentylenetetrazole-induced seizures in rats

In the present study the contribution of estradiol in sex-dependent differences of pentylenetetrazole (PTZ)-induced seizures was investigated in rats. The rats were divided into four groups: 1) sham, 2) ovariectomized (OVX), 3) ovariectomized-estradiol (OVX-Est) and 4) male. The OVX-Est group received estradiol valerate (2 mg/kg; i.m/4 weeks) while, male, sham and OVX groups received vehicle. The animals were injected by PTZ (90 mg/kg). The latencies to minimal clonic seizures (MCS) and generalized tonic-clonic seizures (GTCS), were recorded. Serum 17β-estradiol and testosterone levels were also determined using an Elisa kit. GTCS latency in OVX rats was higher than in sham-operated animals (P < 0.05). MCS and GTCS latency in the male group was significantly higher than in the sham, OVX and OVX-Est groups (P < 0.001 and P < 0.01). There was no significant difference in MCS or GTCS latencies among OVX-Est, sham and OVX groups. Serum 17β-estradiol level in the OVX group was significantly lower than in the sham (P < 0.01) and in the OVX-Est group it was higher than in the sham, OVX and male groups (P < 0.01 and P < 0.001). Serum testosterone level in the male group was significantly higher than in all the other three groups (P < 0.001). It seems that testosterone probably has a more efficient role than estradiol in the gender dependent difference in seizure caused by PTZ in rats.

Role of hormones and neurosteroids in epileptogenesis

This article describes the emerging evidence of hormonal influence on epileptogenesis, which is a process whereby a brain becomes progressively epileptic due to an initial precipitating event of diverse origin such as brain injury, stroke, infection, or prolonged seizures. The molecular mechanisms underlying the development of epilepsy are poorly understood. Neuroinflammation and neurodegeneration appear to trigger epileptogenesis. There is an intense search for drugs that truly prevent the development of epilepsy in people at risk. Hormones play an important role in children and adults with epilepsy. Corticosteroids, progesterone, estrogens, and neurosteroids have been shown to affect seizure activity in animal models and in clinical studies. However, the impact of hormones on epileptogenesis has not been investigated widely. There is emerging new evidence that progesterone, neurosteroids, and endogenous hormones may play a role in regulating the epileptogenesis. Corticosterone has excitatory effects and triggers epileptogenesis in animal models. Progesterone has disease-modifying activity in epileptogenic models. The antiepileptogenic effect of progesterone has been attributed to its conversion to neurosteroids, which binds to GABA-A receptors and enhances phasic and tonic inhibition in the brain. Neurosteroids are robust anticonvulsants. There is pilot evidence that neurosteroids may have antiepileptogenic properties. Future studies may generate new insight on the disease-modifying potential of hormonal agents and neurosteroids in epileptogenesis.

Dehydroepiandrosterone's antiepileptic action in FeCl3-induced epileptogenesis involves upregulation of glutamate transporters

Dehydroepiandrosterone (DHEA), a neuroactive androgen steroid, has antiepileptic action in iron-induced experimental epilepsy (which models post-traumatic clinical epilepsy). In iron-induced epilepsy increased extracellular glutamate resulting from its reduced glial uptake due to the down-regulation (decreased expression) of transporters (glial and or neuronal) is active during epileptogenesis. The present study was aimed at determining whether the mechanism of antiepileptic action of DHEA involved upregulation (increased expression) of glutamate transporters. Iron-induced epileptogenesis was performed in rats by FeCl3 injection into the cerebral cortex. DHEA was administered intraperitoneally to the iron-induced epileptic rats for 7, 14 and 21 days. Levels of glutamate transporters mRNAs expression were measured using quantitative PCR in the hippocampus during the chronic phase of iron-induced epileptogenesis. There were significant reductions in the glutamate transporter mRNAs in epileptogenesis. DHEA treatment resulted in a significant elevation of glutamate transporters: GLT-1, GLAST and EACC-1 mRNA indicating that the DHEA treatment induced upregulation of these transporters. The results are of significance in respect of the mechanism of the antiepileptic action of neurosteroids and the glutamate transporters as therapeutic targets in glutamatergic epileptogenesis.

Differences in vulnerability to nicotine-induced kindling between female and male periadolescent rats

RATIONALE

It has recently been reported that chronic nicotine administration at subconvulsive doses causes seizures, a phenomenon referred to as kindling. Evidence points to the involvement of oxidative stress in pharmacological and electrical kindling, sex is known to influence the brain's response to nicotine.

OBJECTIVES

This study investigated the sex differences in vulnerability to nicotine-induced kindling and the involvement of oxidative stress in this phenomenon.

METHODS

Male and female periadolescent Wistar rats received repeated injections of a subconvulsive dose of nicotine (hemisulfate salt; 2 mg/kg, i.p.) every weekday for up to 25 days. To better understand the influence of oxidative stress in nicotine kindling, the antioxidant vitamin E (200 and 400 mg/kg, p.o.) was administered prior to nicotine administration. The levels of gluthatione (GSH), superoxide dismutase (SOD) activity, and lipid peroxidation were determined in the hippocampus (HC), prefrontal cortex (PFC), and striatum.

RESULTS

Female animals developed kindling more rapidly than male rats. In female rats, kindling was associated with decreases in antioxidant defenses, including GSH levels in the HC and striatum and SOD activity in the PFC and striatum, and increased lipid peroxidation in all brain areas studied. By contrast, male kindled animals presented only with a decrease in the GSH in the HC. Vitamin E prevented the occurrence of kindled seizures by 80 % and 75 % in male and female rats, respectively.

CONCLUSION

These novel findings indicate that female periadolescent rats develop nicotine-kindled seizures earlier than their male counterparts. Differences in the oxidative balance may be involved in this mechanism.

The steroid metabolome in lamotrigine-treated women with epilepsy

BACKGROUND

Epilepsy in women may be associated with reproductive disorders and alterations in serum steroid levels. Some steroids can be induced by epilepsy and/or treatment with antiepileptic drugs; however, there are still limited data available concerning this effect on the levels of other neuroactive steroid metabolites such as 3a-hydroxy-5a/b-reduced androstanes.

AIM

To evaluate steroid alterations in women with epilepsy (WWE) on lamotrigine monotherapy.

SUBJECTS AND METHODS

Eleven WWE and 11 age-matched healthy women underwent blood sampling in both phases of their menstrual cycles (MCs). The steroid metabolome, which included 30 unconjugated steroids, 17 steroid polar conjugates, gonadotropins, and sex hormone-binding globulin (SHBG), was measured using gas chromatography-mass spectrometry (GC-MS) and radioimmunoassay (RIA).

RESULTS

WWE had lower cortisol levels (status p<0.001), but elevated levels of unconjugated 17-hydroxypregnenolone (status p<0.001). Progesterone was higher in the follicular menstrual phase (FP) in WWE than in the controls (status×menstrual phase p<0.05, Bonferroni multiple comparisons p<0.05), whereas 17-hydroxyprogesterone was higher in WWE in both menstrual phases (status p<0.001). The steroid conjugates were mostly elevated in WWE. The levels of 5α/β-reduced androstanes in WWE that were significantly higher than the controls were etiocholanolone (status p<0.001), 5α-androstane-3α,17β-diol (status p<0.001), and the 5α/β-reduced androstane polar conjugates (status p<0.001).

CONCLUSIONS

WWE showed a trend toward higher circulating 3α-hydroxy-5α/β-reduced androstanes, increased activity of 17α-hydroxylase/17,20 lyase in the Δ(5)-steroid metabolic pathway, and increased levels of the steroid polar conjugates.

Molecular aspects involved in swimming exercise training reducing anhedonia in a rat model of depression

Patients suffering from depression frequently display hyperactivity of the hypothalamic-pituitary-adrenal axis (HPA) resulting in elevated cortisol levels. One main symptom of this condition is anhedonia. There is evidence that exercise training can be used as a rehabilitative intervention in the treatment of depressive disorders. In this scenario, the aim of the present study was to assess the effect of an aerobic exercise training protocol on the depressive-like behavior, anhedonia, induced by repeated dexamethasone administration. The study was carried out on adult male Wistar rats randomly divided into four groups: the "control group" (C), "exercise group" (E), "dexamethasone group" (D) and the "dexamethasone plus exercise group" (DE). The exercise training consisted of swimming (1 h/d, 5 d/wk) for 3 weeks, with an overload of 5% of the rat body weight. Every day rats were injected with either dexamethasone (D/DE) or saline solution (C/E). Proper positive controls, using fluoxetine, were run in parallel. Decreased blood corticosterone levels, reduced adrenal cholesterol synthesis and adrenal weight (HPA disruption), reduced preference for sucrose consumption and increased immobility time (depressive-like behavior), marked hippocampal DNA oxidation, increased IL-10 and total brain-derived neurotrophic factor (BDNF; pro-plus mature-forms) and a severe loss of body mass characterized the dexamethasone-treated animals. Besides increasing testosterone blood concentrations, the swim training protected depressive rats from the anhedonic state, following the same profile as fluoxetine, and also from the dexamethasone-induced impaired neurochemistry. The data indicate that physical exercise could be a useful tool in preventing and treating depressive disorders.

Neuroprotective actions of neurosteroids

Neurosteroids were initially defined as steroid hormones locally synthesized within the nervous tissue. Subsequently, they were described as steroid hormone derivatives that devoid hormonal action but still affect neuronal excitability through modulation of ionotropic receptors. Neurosteroids are further subdivided into natural (produced in the brain) and synthetic. Some authors distinguish between hormonal and regular neurosteroids in the group of natural ones. The latter group, including hormone metabolites like allopregnanolone or tetrahydrodeoxycorticosterone, is devoid of hormonal activity. Both hormones and their derivatives share, however, most of the physiological functions. It is usually very difficult to distinguish the effects of hormones and their metabolites. All these substances may influence seizure phenomena and exhibit neuroprotective effects. Neuroprotection offered by steroid hormones may be realized in both genomic and non-genomic mechanisms and involve regulation of the pro- and anti-apoptotic factors expression, intracellular signaling pathways, neurotransmission, oxidative, and inflammatory processes. Since regular neurosteroids show no affinity for steroid receptors, they may act only in a non-genomic mode. Multiple studies have been conducted so far to show efficacy of neurosteroids in the treatment of the central and peripheral nervous system injury, ischemia, neurodegenerative diseases, or seizures. In this review we focused primarily on neurosteroid mechanisms of action and their role in the process of neurodegeneration. Most of the data refers to results obtained in experimental studies. However, it should be realized that knowledge about neuroactive steroids remains still incomplete and requires confirmation in clinical conditions.

Antiepileptic action of exogenous dehydroepiandrosterone in iron-induced epilepsy in rat brain

In the study described here, the antiepileptic effect of dehydroepiandrosterone (DHEA) treatment on iron-induced focal epileptiform activity in the rat brain was investigated. DHEA is a neuroactive corticosteroid hormone synthesized both in the adrenal cortex and in the brain. Its antioxidant properties are well known. As oxidative stress seems to play a major role in epileptogenesis in the iron-induced model of posttraumatic epilepsy, it was of interest to examine whether DHEA would exert antiepileptic activity. DHEA at a dose of 30 mg/kg/day administered intraperitoneally for 7, 14, and 21 days to iron-induced epileptic rats prevented epileptiform electrophysiological activity. Morris water maze and open-field tests on iron-induced epileptic rats revealed that DHEA also prevented behavioral alterations related to epileptiform activity. Thus, DHEA attenuated the cognitive defects produced by epileptic activity. Moreover, alterations in epileptogenesis-related biochemical parameters-lipid peroxidation, protein oxidation and Na(+), K(+)-ATPase (sodium pump) activity--were also countered by DHEA.

The testosterone-derived neurosteroid androstanediol is a positive allosteric modulator of GABAA receptors

Testosterone modulates seizure susceptibility, but the underlying mechanisms are obscure. Recently, we demonstrated that testosterone affects seizure activity via its conversion to neurosteroids in the brain. Androstanediol (5alpha-androstan-3alpha,17beta-diol) is an endogenous neurosteroid synthesized from testosterone. However, the molecular mechanism underlying the seizure protection activity of androstanediol remains unclear. Here, we show that androstanediol has positive allosteric activity as a GABA(A) receptor modulator. In whole-cell recordings from acutely dissociated hippocampus CA1 pyramidal cells, androstanediol (but not its 3beta-epimer) produced a concentration-dependent enhancement of GABA-activated currents (EC(50) of 5 microM). At 1 microM, androstanediol produced a 50% potentiation of GABA responses. In the absence of GABA, androstanediol has moderate direct effects on GABA(A) receptor-mediated currents at high concentrations. Systemic doses of androstanediol (5-100 mg/kg), but not its 3beta-epimer, caused dose-dependent suppression of behavioral and electrographic seizures in mouse hippocampus kindling, which is a model of temporal lobe epilepsy. The ED(50) value for antiseizure effects of androstanediol was 50 mg/kg, which did not produce sedation/motor toxicity. At high (2x ED(50)) doses, androstanediol produced complete seizure protection that lasted for up to 3 h after injection. The estimated plasma concentrations of androstanediol producing 50% seizure protection in the kindling model (10.6 microM) are within the range of concentrations that modulate GABA(A) receptors. These studies suggest that androstanediol could be a neurosteroid mediator of testosterone actions on neuronal excitability and seizure susceptibility via its activity as a GABA(A) receptor modulator and that androstanediol may play a key role in men with epilepsy, especially during the age-related decline in androgen levels.

Antiseizure effects of 3alpha-androstanediol and/or 17beta-estradiol may involve actions at estrogen receptor beta

Testosterone (T), the principal androgen secreted by the testes, can have antiseizure effects. Some of these effects may be mediated by T's metabolites. T is metabolized to 3alpha-androstanediol (3alpha-diol). T, but not 3alpha-diol, binds androgen receptor. We investigated effects of 3alpha-diol (1 mg/kg, SC) and/or an androgen receptor blocker (flutamide 10 mg, SC), 1 hour prior to administration of pentylenetetrazol (85 mg/kg, IP). Juvenile male rats administered 3alpha-diol had less seizure activity than those administered vehicle. Flutamide had no effects. T is aromatized to 17beta-estradiol (E(2)), which, like 3alpha-diol, acts at estrogen receptors (ERs). Selective estrogen receptor modulators that favor ERalpha (propyl pyrazole triol, 17alpha-E(2)) or ERbeta (diarylpropionitrile, coumestrol, 3alpha-diol), or both (17beta-E(2)), were administered (0.1 mg/kg, SC) to juvenile male rats 1 hour before pentylenetetrazol. Estrogens with activity at ERbeta, but not those selective for ERalpha, produced antiseizure effects. Actions at ERbeta may underlie some antiseizure effects of T's metabolites.

Chronic administration of androgens with actions at estrogen receptor beta have anti-anxiety and cognitive-enhancing effects in male rats

Androgen levels decline with aging. Some androgens may exert anti-anxiety and cognitive-enhancing effects; however, determining which androgens have anxiolytic-like and/or mnemonic effects is of interest given the different mechanisms that may underlie some of their effects. For example, the 5 alpha-reduced metabolite of testosterone (T), dihydrotesterone, can be further converted to 5 alpha-androstane,17beta-diol-3 alpha-diol (3 alpha-diol) and 5 alpha-androstane,17beta-diol-3beta-diol (3beta-diol), both of which bind with high affinity to the beta isomer of the intracellular estrogen receptor beta (ER beta). However, androsterone, another metabolite of T, does not bind well to ER beta. To investigate the effects of T metabolites, male rats were subjected to gonadectomy then implanted with silastic capsules of 3 alpha-diol, 3beta-diol, androsterone, or oil control. After recovery, the rats were tested in elevated plus maze (EPM), light/dark transition (LD), and Morris water maze (MWM). 3 alpha-diol both decreased anxiety-like behavior in the EPM and LD, and increased cognition in MWM, while 3beta-diol improved cognition in MWM, but had no effects on anxiety behavior, compared to vehicle or androsterone. These data suggest that the actions of 3 alpha-diol and 3beta-diol at ER beta may be responsible for some of testosterone's anti-anxiety and cognitive-enhancing effects.

Sex differences in acute ethanol withdrawal severity after adrenalectomy and gonadectomy in Withdrawal Seizure-Prone and Withdrawal Seizure-Resistant mice

Recent findings suggest that the ability of ethanol (EtOH) to increase the levels of neurosteroids with potent gamma-aminobutyric acid (GABA)ergic properties can influence measures of EtOH sensitivity. Earlier studies determined that removal of the adrenals and gonads diminished the steroidogenic effect of EtOH and significantly increased acute EtOH withdrawal severity in two inbred mouse strains that differed in withdrawal severity, suggesting the contribution of anticonvulsant GABAergic steroids to acute withdrawal in intact animals. Thus, the goal of the present study was to investigate the consequence of steroid removal on acute EtOH withdrawal through excision of the adrenals and gonads, in another genetic animal model of EtOH withdrawal differences, the Withdrawal Seizure-Prone (WSP) and Withdrawal Seizure-Resistant (WSR) selected lines. Male and female WSP and WSR mice underwent surgical removal of the adrenals and gonads or no organ removal (SHAM). One to 2 weeks later, baseline handling-induced convulsions (HICs) were assessed, mice were given a 4 g/kg dose of EtOH, and HICs were measured hourly for 12 h and then at 24 h. The combination surgery significantly increased EtOH withdrawal in WSP and WSR female mice, as measured by area under the curve (AUC) and peak HIC scores. The AUC was significantly positively correlated with plasma corticosterone levels and significantly negatively correlated with progesterone levels. In contrast, surgical status did not alter withdrawal severity in male WSP and WSR mice. Overall, the increase in acute EtOH withdrawal severity in female WSP and WSR mice after adrenalectomy and gonadectomy corroborate our recent evidence that withdrawal from a high dose of EtOH can be modulated by anticonvulsant steroids produced in the periphery.

The role of neurosteroids in the pathophysiology and treatment of catamenial epilepsy

Catamenial epilepsy is a multifaceted neuroendocrine condition in which seizures are clustered around specific points in the menstrual cycle, most often around perimenstrual or periovulatory period. Generally, a twofold or greater increase in seizure frequency during a particular phase of the menstrual cycle could be considered as catamenial epilepsy. Based on this criteria, recent clinical studies indicate that catamenial epilepsy affects 31-60% of the women with epilepsy. Three types of catamenial seizures (perimenstrual, periovulatory and inadequate luteal) have been identified. However, there is no specific drug available today for catamenial epilepsy, which has not been successfully treated with conventional antiepileptic drugs. Elucidation of the pathophysiology of catamenial epilepsy is a prerequisite to develop specific targeted approaches for treatment or prevention of the disorder. Cyclical changes in the circulating levels of estrogens and progesterone play a central role in the development of catamenial epilepsy. There is emerging evidence that endogenous neurosteroids with anticonvulsant or proconvulsant effects could play a critical role in catamenial epilepsy. It is thought that perimenstrual catamenial epilepsy is associated with the withdrawal of anticonvulsant neurosteroids. Progesterone and other hormonal agents have been shown in limited trials to be moderately effective in catamenial epilepsy, but may cause endocrine side effects. Synthetic neurosteroids, which enhance the tonic GABA-A receptor function, might provide an effective approach for the catamenial epilepsy therapy without producing hormonal side effects.

Protective actions of sex steroid hormones in Alzheimer's disease

Risk for Alzheimer's disease (AD) is associated with age-related loss of sex steroid hormones in both women and men. In post-menopausal women, the precipitous depletion of estrogens and progestogens is hypothesized to increase susceptibility to AD pathogenesis, a concept largely supported by epidemiological evidence but refuted by some clinical findings. Experimental evidence suggests that estrogens have numerous neuroprotective actions relevant to prevention of AD, in particular promotion of neuron viability and reduction of beta-amyloid accumulation, a critical factor in the initiation and progression of AD. Recent findings suggest neural responsiveness to estrogen can diminish with age, reducing neuroprotective actions of estrogen and, consequently, potentially limiting the utility of hormone therapies in aged women. In addition, estrogen neuroprotective actions are also modulated by progestogens. Specifically, continuous progestogen exposure is associated with inhibition of estrogen actions whereas cyclic delivery of progestogens may enhance neural benefits of estrogen. In recent years, emerging literature has begun to elucidate a parallel relationship of sex steroid hormones and AD risk in men. Normal age-related testosterone loss in men is associated with increased risk to several diseases including AD. Like estrogen, testosterone has been established as an endogenous neuroprotective factor that not only increases neuronal resilience against AD-related insults, but also reduces beta-amyloid accumulation. Androgen neuroprotective effects are mediated both directly by activation of androgen pathways and indirectly by aromatization to estradiol and initiation of protective estrogen signaling mechanisms. The successful use of hormone therapies in aging men and women to delay, prevent, and or treat AD will require additional research to optimize key parameters of hormone therapy and may benefit from the continuing development of selective estrogen and androgen receptor modulators.

Chronic administration of androgens with actions at estrogen receptor beta have anti-anxiety and cognitive-enhancing effects in male rats

Androgen levels decline with aging. Some androgens may exert anti-anxiety and cognitive-enhancing effects; however, determining which androgens have anxiolytic-like and/or mnemonic effects is of interest given the different mechanisms that may underlie some of their effects. For example, the 5 alpha-reduced metabolite of testosterone (T), dihydrotesterone, can be further converted to 5 alpha-androstane,17beta-diol-3 alpha-diol (3 alpha-diol) and 5 alpha-androstane,17beta-diol-3beta-diol (3beta-diol), both of which bind with high affinity to the beta isomer of the intracellular estrogen receptor beta (ER beta). However, androsterone, another metabolite of T, does not bind well to ER beta. To investigate the effects of T metabolites, male rats were subjected to gonadectomy then implanted with silastic capsules of 3 alpha-diol, 3beta-diol, androsterone, or oil control. After recovery, the rats were tested in elevated plus maze (EPM), light/dark transition (LD), and Morris water maze (MWM). 3 alpha-diol both decreased anxiety-like behavior in the EPM and LD, and increased cognition in MWM, while 3beta-diol improved cognition in MWM, but had no effects on anxiety behavior, compared to vehicle or androsterone. These data suggest that the actions of 3 alpha-diol and 3beta-diol at ER beta may be responsible for some of testosterone's anti-anxiety and cognitive-enhancing effects.

Hormonal influences on seizures: basic neurobiology

There are sex differences and effects of steroid hormones, such as androgens, estrogens, and progestogens, that influence seizures. Androgens exert early organizational and later activational effects that can amplify sex/gender differences in the expression of some seizure disorders. Female-typical sex steroids, such as estrogen (E2) and progestins, can exert acute activational effects to reduce convulsive seizures and these effects are mediated in part by the actions of steroids in the hippocampus. Some of these anticonvulsive effects of sex steroids are related to their formation of ligands which have agonist-like actions at gamma-aminobutyric acid (GABAA) receptors or antagonist actions at glutamatergic receptors. Differences in stress, developmental phase, reproductive status, endocrine status, and treatments, such as anti-epileptic drugs (AEDs), may alter levels of these ligands and/or the function of target sites, which may mitigate differences in sensitivity to, and/or tolerance of, steroids among some individuals. The evidence implicating sex steroids in differences associated with hormonal, reproductive, developmental, stress, seizure type, and/or therapeutics are discussed.

Antiseizure effects of 5*-androstane-3*,7beta-diol may be independent of actions at estrogen receptor beta

Testosterone (T), the principal androgen secreted by the testes, can have antiseizure effects; however, the mechanism(s) underlying this action is not well understood. T is metabolized to dihydrotestosterone (DHT) by the enzyme 5*-reductase. DHT is then converted to 5*-androstane-3*,17beta-diol (3*-diol) by the enzyme 3*-hydroxysteroid dehydrogenase. T and DHT bind with high affinity to intracellular androgen receptors; however, 3*-diol does not. The mnemonic effects of 3*-diol are mediated in part through the beta isoform of estrogen receptors (ERbeta) in the hippocampus. As such, we investigated whether 3*-diol has antiseizure effects in mice that require action at ERbeta. 3*-Diol (2 mg/kg subcutaneously) was administered to wild-type C57/B6 mice and heterozygous and homozygous ERbeta knockout (betaERKO) mice 1 hour prior to administration of pentylenetetrazol (PTZ; 85 mg/kg intraperitoneally). Mice administered 3*-diol had significantly longer latencies to clonic seizure and death and lower seizure scores than did mice administered vehicle. This pattern of effects was observed in wild-type or betaERKO mice. Thus, for these mice, the antiseizure effects of 3*-diol for the chemoconvulsant PTZ occur independent of actions at ERbeta.

Androgen cell signaling pathways involved in neuroprotective actions

As a normal consequence of aging in men, testosterone levels significantly decline in both serum and brain. Age-related testosterone depletion results in increased risk of dysfunction and disease in androgen-responsive tissues, including brain. Recent evidence indicates that one deleterious effect of age-related testosterone loss in men is increased risk for Alzheimer's disease (AD). We discuss recent findings from our laboratory and others that identify androgen actions implicated in protecting the brain against neurodegenerative diseases and begin to define androgen cell signaling pathways that underlie these protective effects. Specifically, we focus on the roles of androgens as (1) endogenous negative regulators of beta-amyloid accumulation, a key event in AD pathogenesis, and (2) neuroprotective factors that utilize rapid non-genomic signaling to inhibit neuronal apoptosis. Continued elucidation of cell signaling pathways that contribute to protective actions of androgens should facilitate the development of targeted therapeutic strategies to combat AD and other age-related neurodegenerative diseases.

Testosterone and nucleus accumbens dopamine in the male Syrian hamster

Most drugs of abuse increase dopamine (DA) in nucleus accumbens (Acb). However, the effects of anabolic androgenic steroids (AAS) on Acb DA have not been examined. We determined the effects of subcutaneous (sc) testosterone (T) on Acb DA in male hamsters. The effects of sc amphetamine were also examined for comparison. In addition, Acb DA was evaluated during intracerebroventricular (ICV) T infusion, designed to mimic T intake during ICV T self-administration in drug-naïve and drug-preexposed animals. Acb DA was measured using in vivo microdialysis and HPLC-EC. T (7.5 or 37.5 mg/kg), amphetamine (1 or 5 mg/kg), or vehicle was injected sc and Acb DA monitored for 4h. In the ICV experiment, T (1 or 2 microg/infusion) or vehicle was infused ICV every 6 min for 4h and Acb DA monitored. ICV T preexposure was accomplished by repeating the same ICV T infusion (1 microg/infusion) daily for 14 days, and T infusion was accompanied by microdialysis on 15th day. Neither sc nor ICV T administration increased Acb DA. At high dose (2 microg/infusion), ICV T decreased Acb DA. Likewise, daily ICV infusion of T for 15 days did not alter Acb DA. In contrast, sc amphetamine significantly increased Acb DA at both doses. Therefore, unlike many drugs of abuse, AAS does not increase Acb DA levels. The reduction in DA at high T doses is likely due to autonomic depressant effects of AAS. We suggest that AAS act via mechanism distinct from those of stimulants, but may share neural substrates with other drugs of abuse.

The impact of gonadectomy and adrenalectomy on acute withdrawal severity in male and female C57BL/6J and DBA/2J mice following a single high dose of ethanol

BACKGROUND

Steroid hormones can influence neuronal excitability and subsequent seizure susceptibility through genomic and nongenomic mechanisms. For example, there are proconvulsant steroids such as estradiol and corticosterone and anticonvulsant steroids such as testosterone, progesterone, and their GABAergic metabolites. Recent findings indicated that a single, acute administration of ethanol increased levels of GABAergic steroids and that the source of this increase was peripheral organs such as the adrenals and gonads. Thus, the purpose of the present study was to determine the impact of removal of the adrenals and/or gonads on withdrawal severity following a single high dose of ethanol in 2 genotypes that differ in ethanol withdrawal severity.

METHOD

Male and female C57BL/6J (B6) and DBA/2J (D2) mice were either left intact (SHAM), adrenalectomized (ADX), gonadectomized (GDX), or underwent ADX/GDX surgery. Seven days following surgery, baseline handling-induced convulsions (HICs) were measured prior to administration of a 4 g/kg dose of ethanol. HICs were assessed following the ethanol injection, then hourly for 12 hours and at 24 hours. A separate group of mice were used to measure the impact of surgical status on ethanol metabolism at 30, 60, 120, and 240 minutes after a single 4 g/kg dose of ethanol.

RESULTS

ADX and ADX/GDX treatments in male B6 and D2 mice increased ethanol withdrawal severity following a single dose of ethanol, measured by area under the withdrawal curve and peak HIC scores. Acute ethanol withdrawal also was increased in female D2 mice that had undergone ADX/GDX. In contrast, surgical status did not alter ethanol withdrawal severity in female B6 mice. Surgical status had only minor effects on ethanol metabolism.

CONCLUSIONS

Removal of peripherally derived steroids with anticonvulsant properties significantly increased HIC scores during acute ethanol withdrawal following a single dose of ethanol in male and female D2 mice and in male B6 mice. These increases were not due to changes in ethanol metabolism.

Progesterone: Therapeutic opportunities for neuroprotection and myelin repair

Progesterone and its metabolites promote the viability of neurons in the brain and spinal cord. Their neuroprotective effects have been documented in different lesion models, including traumatic brain injury (TBI), experimentally induced ischemia, spinal cord lesions and a genetic model of motoneuron disease. Progesterone plays an important role in developmental myelination and in myelin repair, and the aging nervous system appears to remain sensitive to some of progesterone's beneficial effects. Thus, the hormone may promote neuroregeneration by several different actions by reducing inflammation, swelling and apoptosis, thereby increasing the survival of neurons, and by promoting the formation of new myelin sheaths. Recognition of the important pleiotropic effects of progesterone opens novel perspectives for the treatment of brain lesions and diseases of the nervous system. Over the last decade, there have been a growing number of studies showing that exogenous administration of progesterone or some of its metabolites can be successfully used to treat traumatic brain and spinal cord injury, as well as ischemic stroke. Progesterone can also be synthesized by neurons and by glial cells within the nervous system. This finding opens the way for a promising therapeutic strategy, the use of pharmacological agents, such as ligands of the translocator protein (18 kDa) (TSPO; the former peripheral benzodiazepine receptor or PBR), to locally increase the synthesis of steroids with neuroprotective and neuroregenerative properties. A concept is emerging that progesterone may exert different actions and use different signaling mechanisms in normal and injured neural tissue.

Testosterone decreases reactive astroglia and reactive microglia after brain injury in male rats: role of its metabolites, oestradiol and dihydrotestosterone

Previous studies have shown that the neuroprotective hormone, testosterone, administered immediately after neural injury, reduces reactive astrogliosis. In this study we have assessed the effect of early and late therapy with testosterone or its metabolites, oestradiol and dihydrotestosterone, on reactive astroglia and reactive microglia after a stab wound brain injury in orchidectomized Wistar rats. Animals received daily s.c. injections of testosterone, oestradiol or dihydrotestosterone on days 0-2 or on days 5-7 after injury. The number of vimentin immunoreactive astrocytes and the volume fraction of major histocompatibility complex-II (MHC-II) immunoreactive microglia were estimated in the hippocampus in the lateral border of the wound. Both early and delayed administration of testosterone or oestradiol, but not dihydrotestosterone, resulted in a significant decrease in the number of vimentin-immunoreactive astrocytes. The volume fraction of MHC-II immunoreactive microglia was significantly decreased in the animals that received testosterone or oestradiol in both early and delayed treatments and in animals that received early dihydrotestosterone administration. Thus, both early and delayed administration of testosterone reduces reactive astroglia and reactive microglia and these effects may be at least in part mediated by oestradiol, while dihydrotestosterone may mediate part of the early effects of testosterone on reactive microglia. In conclusion, testosterone controls reactive gliosis and its metabolites, oestradiol and dihydrotestosterone, may be involved in this hormonal effect. The regulation of gliosis may be part of the neuroprotective mechanism of testosterone.

Nanomolar concentrations of anabolic-androgenic steroids amplify excitotoxic neuronal death in mixed mouse cortical cultures

The use of anabolic-androgenic steroids (AASs) in the world of sport has raised a major concern for the serious, sometimes life-threatening, side effects associated with these drugs. Most of the CNS effects are of psychiatric origin, and whether or not AASs are toxic to neurons is yet unknown. We compared the effect of testosterone with that of the AASs, 19-nortestosterone (nandrolone), stanozolol, and gestrinone, on excitotoxic neuronal death induced by N-methyl-d-aspartate (NMDA) in primary cultures of mouse cortical cells. In the most relevant experiments, steroids were applied to the cultures once daily during the 4 days preceding the NMDA pulse. Under these conditions, testosterone amplified excitotoxic neuronal death only at very high concentrations (10 muM), whereas it was protective at concentrations of 10 nM and inactive at intermediate concentrations. Low concentrations of testosterone became neurotoxic in the presence of the aromatase inhibitors, i.e. anastrozole and aminoglutethimide, suggesting that the intrinsic toxicity of testosterone was counterbalanced by its aromatization into 17beta-estradiol. As opposed to testosterone, nortestosterone, stanozolol and gestrinone amplified NMDA toxicity at nanomolar concentrations; their action was insensitive to aromatase inhibitors, but was abrogated by the androgen receptor antagonist, flutamide. None of the AASs were toxic in the absence of NMDA. These data suggest that AASs increase neuronal vulnerability to an excitotoxic insult and may therefore facilitate neuronal death associated with acute or chronic CNS disorders.

Androgen regulation of beta-amyloid protein and the risk of Alzheimer's disease

Advancing age is the most significant risk factor for the development of Alzheimer's disease (AD), however the age-related changes that underlie this effect remain unclear. In men, one normal consequence of aging is a robust decline in circulating and brain levels of the sex steroid hormone testosterone. Testosterone depletion leads to functional impairments and increased risk of disease in androgen-responsive tissues throughout the body, including brain. In this review we discuss the relationship between age-related testosterone depletion and the development of AD. Specifically, we focus on androgen regulation of beta-amyloid protein (Abeta), the accumulation of which is a key initiating factor in AD pathogenesis. Emerging data suggest that the regulatory actions of androgens on both Abeta and the development of AD support consideration of androgen therapy for the prevention and treatment of AD.

Mass spectrometric assay and physiological-pharmacological activity of androgenic neurosteroids

Steroid hormones play a key role in the pathophysiology of several brain disorders. Testosterone modulates neuronal excitability, but the underlying mechanisms are obscure. There is emerging evidence that testosterone-derived "androgenic neurosteroids", 3alpha-androstanediol and 17beta-estradiol, mediate the testosterone effects on neural excitability and seizure susceptibility. Testosterone undergoes metabolism to neurosteroids via two distinct pathways. Aromatization of the A-ring converts testosterone into 17beta-estradiol. Reduction of testosterone by 5alpha-reductase generates 5alpha-dihydrotestosterone, which is then converted to 3alpha-androstanediol, a powerful GABA(A) receptor-modulating neurosteroid with anticonvulsant properties. Although the 3alpha-androstanediol is an emerging neurosteroid in the brain, there is no specific and sensitive assay for determination of 3alpha-androstanediol in biological samples. This article describes the development and validation of mass spectrometric assay of 3alpha-androstanediol, and the molecular mechanisms underlying the testosterone modulation of seizure susceptibility. A liquid chromatography-tandem mass spectrometry assay to measure 3alpha-androstanediol is validated with excellent linearity, specificity, sensitivity, and reproducibility. Testosterone modulation of seizure susceptibility is demonstrated to occur through its conversion to neurosteroids with "anticonvulsant" and "proconvulsant" actions and hence the net effect of testosterone on neural excitability and seizure activity depends on the levels of distinct testosterone metabolites. The proconvulsant effect of testosterone is associated with increases in plasma 17beta-estradiol concentrations. The 5alpha-reduced metabolites of testosterone, 5alpha-dihydrotestosterone and 3alpha-androstanediol, had powerful anticonvulsant activity. Overall, the testosterone-derived neurosteroids 3alpha-androstanediol and 17beta-estradiol could contribute to the net cellular actions of testosterone in the brain. Because 3alpha-androstanediol is a potent positive allosteric modulator of GABA(A) receptors, it could serve as an endogenous neuromodulator of neuronal excitability in men. The 3alpha-androstanediol assay is an important tool in this area because of the growing interest in the potential to use adjuvant aromatase inhibitor therapy to improve treatment of epilepsy.

Puberty, hormones, and sex differences in alcohol abuse and dependence

Sex differences in patterns of drinking and rates of alcohol abuse and dependence begin to emerge during the transition from late puberty to young adulthood. Increases in pubertal hormones, including gonadal and stress hormones, are a prominent developmental feature of adolescence and could contribute to the progression of sex differences in alcohol drinking patterns during puberty. This paper reviews experimental and correlational studies of gonadal and stress-related hormone changes and their effects on alcohol drinking and other associated actions of alcohol. Mechanisms are suggested by which reproductive hormones and stress-related hormones may modulate neural circuits within the brain reward system to produce sex differences in alcohol drinking patterns and vulnerability to alcohol abuse and dependence which become apparent during the late pubertal period.

A new look at the 5alpha-reductase inhibitor finasteride

Finasteride is the first 5alpha-reductase inhibitor that received clinical approval for the treatment of human benign prostatic hyperplasia (BPH) and androgenetic alopecia (male pattern hair loss). These clinical applications are based on the ability of finasteride to inhibit the Type II isoform of the 5alpha-reductase enzyme, which is the predominant form in human prostate and hair follicles, and the concomitant reduction of testosterone to dihydrotestosterone (DHT). In addition to catalyzing the rate-limiting step in the reduction of testosterone, both isoforms of the 5alpha-reductase enzyme are responsible for the reduction of progesterone and deoxycorticosterone to dihydroprogesterone (DHP) and dihydrodeoxycorticosterone (DHDOC), respectively. Recent preclinical data indicate that the subsequent 3alpha-reduction of DHT, DHP and DHDOC produces steroid metabolites with rapid non-genomic effects on brain function and behavior, primarily via an enhancement of gamma-aminobutyric acid (GABA)ergic inhibitory neurotransmission. Consistent with their ability to enhance the action of GABA at GABA(A) receptors, these steroid derivatives (termed neuroactive steroids) possess anticonvulsant, antidepressant and anxiolytic effects in addition to altering aspects of sexual- and alcohol-related behaviors. Thus, finasteride, which inhibits both isoforms of 5alpha-reductase in rodents, has been used as a tool to manipulate neuroactive steroid levels and determine the impact on behavior. Results of some preclinical studies and clinical observations with finasteride are described in this review article. The data suggest that endogenous neuroactive steroid levels may be inversely related to symptoms of premenstrual and postpartum dysphoric disorder, catamenial epilepsy, depression, and alcohol withdrawal.

Role of androgens in epilepsy

Accumulating evidence suggests that both male- and/or female-typical sex steroids contribute to seizure susceptibility in epilepsy. Although there is rich literature regarding how female-typical sex steroids, such as progestins and estrogens, influence epilepsy, the role of androgens in seizure processes are just beginning to be understood. Given that some of the effects and mechanisms of androgen action on ictal activity may converge with that of progestins and/or estrogens, this review discusses what is known concerning the role of each of these sex steroids on seizures. Additionally, evidence that seizures and/or antiepileptic drugs can themselves influence steroid-dependent behaviors, such as affective, cognitive and reproductive function, is also reviewed. Considerations for therapeutic management and future directions for research and drug discovery are summarized.

Neurosteroids, neuroactive steroids, and symptoms of affective disorders

Neurosteroids (NS) are steroids synthesized by the brain. Neuroactive steroids (NAS) refers to steroids that, independent of their origin, are capable of modifying neural activities. NAS bind and modulate different types of membrane receptors. The gamma amino butyric acid (GABA) and sigma receptor complexes have been the most extensively studied. Oxidized ring A reduced pregnanes, tetrahydroprogesterone (THP), and tetrahydrodeoxycorticosterone (THDOC) bind to the progesterone intracellular receptor (PR), and in this way can also regulate gene expression. Animal experimentation showed that salient symptoms of depression, viz., anxiety, sleep disturbances, and memory and sexual dysfunctions, are modulated by NAS. In turn, psychotropic drugs modulate NS and NAS levels. NS levels as well as NAS plasma concentrations change in patients with depression syndromes, the levels return to normal baseline with recovery, but normalization is not necessary for successful therapy. Results from current studies on the evolution of nervous systems, including evolutionary developmental biology as well as anatomical and physiological findings, almost preclude a categorical classification of the psychiatric ailments the human brain succumbs to. The persistence in maintaining such essentialist classifications may help to explain why up to now the search for biological markers in psychiatry has been an unrewarding effort. It is proposed that it would be more fruitful to focus on relationships between NAS and symptoms of psychiatric disorders, rather than with typologically defined disorders.

The relevance of neurosteroids to clinical psychiatry: from the laboratory to the bedside

Neurosteroids are important neuroactive molecules with suggested central involvement in several neurophysiological and psychiatric disease processes. The discovery of neurosteroids followed the revelation that the brain exhibited the capacity to synthesize its own steroids in situ and thus be a potential site of steroidogenesis. In contrast to some steroids that exhibit traditional genomic steroid actions, most neurosteroids appear to regulate neuronal function by means of "non-genomic" mechanisms influencing neuronal excitability. Neurosteroids are synthesized either from CNS cholesterol or from peripheral steroid precursors and exhibit a wide range of modulatory effects on neurotransmitter receptor activity, most notably at the gamma-aminobutyric acid A (GABA(A)) receptor. Neurosteroids play an important role in neurodevelopment and neuroprotective effects, many aspects of which may have particular applicability to psychiatric disorders including various gender differences. Neurosteroids appear to be relevant to the pathophysiology and pharmacological treatment of many psychiatric disorders including the most notable mood and anxiety disorders, but also psychotic, childhood, eating, dementia, stress and postpartum disorders. It has been suggested that neurosteroids may become potential targets for pharmacological intervention in the future with further neurosteroid investigation contributing to a more comprehensive understanding of human behavior and psychopathology.

Androgens, aging, and Alzheimer's disease

Testosterone depletion is a normal consequence of aging in men that is associated with senescent effects in androgen- responsive tissues. We discuss new evidence that one consequence of testosterone depletion in men is an increased risk for the development of Alzheimer's disease (AD). Furthermore, we discuss two candidate mechanisms by which testosterone may affect AD pathogenesis. First, testosterone has been identified as an endogenous regulator of beta-amyloid, a protein that abnormally accumulates in AD brain and is implicated as a causal factor in the disease. Second, findings from several different paradigms indicate that testosterone has both neurotrophic and neuroprotective functions. These new findings support the clinical evaluation of androgen-based therapies for the prevention and treatment of AD.

The pheromone androstenol (5 alpha-androst-16-en-3 alpha-ol) is a neurosteroid positive modulator of GABAA receptors

Androstenol is a steroidal compound belonging to the group of odorous 16-androstenes, first isolated from boar testes and also found in humans. Androstenol has pheromone-like properties in both animals and humans, but the molecular targets of its pheromonal activity are unknown. Androstenol is structurally similar to endogenous A-ring reduced neurosteroids that act as positive modulators of GABA(A) receptors. Here we show that androstenol has neurosteroid-like activity as a GABA(A) receptor modulator. In whole-cell recordings from cerebellar granule cells, androstenol (but not its 3beta-epimer) caused a concentration-dependent enhancement of GABA-activated currents (EC(50), 0.4 microM in cultures; 1.4 microM in slices) and prolonged the duration of spontaneous and miniature inhibitory postsynaptic currents. Androstenol (0.1-1 microM) also potentiated the amplitude of GABA-activated currents in human embryonic kidney 293 cells transfected with recombinant alpha1beta2gamma2 and alpha2beta2gamma2 GABA(A) receptors and, at high concentrations (10-300 microM), directly activated currents in these cells. Systemic administration of androstenol (30-50 mg/kg) caused anxiolytic-like effects in mice in the open-field test and elevated zero-maze and antidepressant-like effects in the forced swim test (5-10 mg/kg). Androstenol, but not its 3beta-epimer, conferred seizure protection in the 6-Hz electroshock and pentylenetetrazol models (ED(50) values, 21.9 and 48.9 mg/kg, respectively). The various actions of androstenol in the whole-animal models are consistent with its activity as a GABA(A) receptor modulator. GABA(A) receptors could represent a target for androstenol as a pheromone, for which it is well suited because of high volatility and lipophilicity, or as a conventional hormonal neurosteroid.

Ketogenic diet decreases circulating concentrations of neuroactive steroids of female rats

Ketogenic diet (KD) is used to manage intractable epilepsy; however, the mechanisms underlying its therapeutic effects are not known. Steroid hormones, such as progesterone and testosterone, are derived from cholesterol, and are readily 5alpha-reduced to dihydroprogesterone and dihydrotestosterone, which are subsequently converted to 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) and 3alpha-androstanediol, neuroactive steroids that can influence seizures. The present study examined the effects of the KD on circulating concentrations of these neuroactive steroids, and their precursors, in intact female rats. Thirty-six, 22-day-old female Sprague-Dawley rats (weaned at 21 days) were fasted for 8 hours prior to placement on one of three dietary regimens for 6 weeks: ad libitum chow, calorie-restricted chow, or KD. After 6 weeks of the diet, when six rats in each dietary condition were in diestrus and six were in behavioral estrus, all rats were administered pentylenetetrazole (PTZ, 70 mg/kg, i.p.). The latency and incidence of seizures were recorded by an observer who was uninformed of the estrous cycle and dietary treatment conditions of the rats. Immediately after each test, trunk blood was obtained for later measurement of pregnane (progesterone, dihydroprogesterone, 3alpha,5alpha-THP) and androstane (testosterone, dihydrotestosterone, 3alpha-androstanediol) neuroactive steroid concentrations in plasma by radioimmunoassay. KD tended to lengthen the latency to, and significantly reduced the number of, PTZ-induced barrel roll seizures. KD also significantly reduced plasma levels of the pregnane (dihydroprogesterone, 3alpha,5alpha-THP) and androstane (dihydrotestosterone, 3alpha-androstanediol) 5alpha-reduced metabolites. These data suggest that levels of pregnane and androstane neuroactive steroids, or their precursors, may underlie some of the antiseizure effects of KD.

Anticonvulsant activity of androsterone and etiocholanolone

PURPOSE

Men with epilepsy often have sexual or reproductive abnormalities that are attributed to alterations in androgen levels, including subnormal free testosterone. Levels of the major metabolites of testosterone-androsterone (5alpha-androstan-3alpha-ol-17-one; 5alpha,3alpha-A), a neurosteroid that acts as a positive allosteric modulator of GABA(A) receptors, and its 5beta-epimer etiocholanolone (5beta-androstan-3alpha-ol-17-one; 5beta,3alpha-A)-also may be reduced in epilepsy. 5alpha,3alpha-A has been found in adult brain, and both metabolites, which also can be derived from androstenedione, are present in substantial quantities in serum along with their glucuronide and sulfate conjugates. This study sought to determine whether these endogenous steroid metabolites can protect against seizures.

METHODS

The anticonvulsant activity of 5alpha,3alpha-A and 5beta,3alpha-A was investigated in electrical and chemoconvulsant seizure models in mice. The steroids also were examined for activity against extracellularly recorded epileptiform discharges in the CA3 region of the rat hippocampal slice induced by perfusion with 55 microM 4-aminopyridine (4-AP).

RESULTS

Intraperitoneal injection of 5alpha,3alpha-A-protected mice in a dose-dependent fashion from seizures in the following models (ED50, dose in mg/kg protecting 50% of animals): 6-Hz electrical stimulation (29.1), pentylenetetrazol (43.5), pilocarpine (105), 4-AP (215), and maximal electroshock (224). 5beta,3alpha-A also was active in the 6-Hz and pentylenetetrazol models, but was less potent (ED50 values, 76.9 and 139 mg/kg, respectively), whereas epiandrosterone (5alpha,3beta-A) was inactive (ED50, <or=300 mg/kg). 5alpha,3alpha-A (10-100 microM) also inhibited epileptiform discharges in a concentration-dependent fashion in the in vitro slice model, whereas 5beta,3alpha-A was active but of lower potency, and 5alpha,3beta-A was inactive.

CONCLUSIONS

5alpha,3alpha-A and 5beta,3alpha-A have anticonvulsant properties. Although of low potency, the steroids are present in high abundance and could represent endogenous modulators of seizure susceptibility.

Steroids, neuroactive steroids and neurosteroids in psychopathology

The term "neurosteroid" (NS) was introduced by Baulieu in 1981 to name a steroid hormone, dehydroepiandrosterone sulfate (DHEAS), that was found at high levels in the brain long after gonadectomy and adrenalectomy, and shown later to be synthetized by the brain. Later, androstenedione, pregnenolone and their sulfates and lipid derivatives as well as tetrahydrometabolites of progesterone (P) and deoxycorticosterone (DOC) were identified as neurosteroids. The term "neuroactive steroid" (NAS) refers to steroids which, independent of their origin, are capable of modifying neural activities. NASs bind and modulate different types of membrane receptors. The GABA and sigma receptor complexes have been the most extensively studied, while glycine-activated chloride channels, nicotinic acetylcholine receptors, voltage-activated calcium channels, although less explored, are also modulated by NASs. Within the glutamate receptor family, N-methyl-d-aspartate (NMDA) receptors, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and kainate receptors have also been demonstrated to be a target for steroid modulation. Besides their membrane effects, once inside the neuron oxidation of Ring A reduced pregnanes, THP and THDOC, bind to the progesterone intracellular receptor and regulate gene expression through this path. The involvement of NASs on depression syndromes, anxiety disorders, stress responses to different stress stimuli, memory processes and related phenomena such as long-term potentiation are reviewed and critically evaluated. The importance of context for the interpretation of behavioral effects of hormones as well as for hormonal levels in body fluids is emphasized. Some suggestions for further research are given.

Androgens in the hippocampus can alter, and be altered by, ictal activity

Steroid hormones, such as androgens, can modulate seizure processes. This review summarizes prior research and presents new data that support the role of androgens in modulating seizure processes. Testosterone, the primary endogenous androgen, has antiseizure effects in people and in animal models of epilepsy. Furthermore, testosterone's antiseizure effects may involve actions of its 5alpha-reduced metabolite and neuroactive steroid, 5alpha-androstane-3alpha,17beta-diol (3alpha-diol). The hippocampus is a target for androgen action and is involved in many types of seizure disorder. Data suggest that actions of androgens in the hippocampus may be important for androgens' antiseizure effects. Interestingly, there may also be a reciprocal relationship between androgens and seizures. Ictal activity can alter the gonadal responsiveness of people with epilepsy and in animal models of seizure disorder. Thus, this paper will review data in support of androgens' antiseizure effects. Further understanding of androgens' role in seizure processes is important for potential therapeutic effects.

Role of neurosteroids in catamenial epilepsy

Catamenial epilepsy is a menstrual cycle-related seizure disorder that affects up to 70% of women with epilepsy. Catamenial epilepsy is characterized by an increase in seizures during particular phases of the menstrual cycle. Three distinct patterns of catamenial epilepsy - perimenstrual, periovulatory, and inadequate luteal phase - have been described. Currently, there is no specific treatment for catamenial epilepsy. The molecular mechanisms involved in the pathophysiology of catamenial epilepsy are not well understood. Recent studies suggest that cyclical changes of ovarian hormones estrogens (proconvulsant) and progesterone (anticonvulsant) appear to play a key role in the genesis of catamenial seizures. Progesterone reduces seizure susceptibility partly through conversion to neurosteroids such as allopregnanolone, which enhances GABA(A) receptor function and thereby inhibits neuronal excitability. In animal models, withdrawal from chronic progesterone and, consequently, of allopregnanolone levels in brain, has been shown to increase seizure susceptibility. Natural progesterone therapy has proven effective in women with epilepsy. Moreover, neurosteroids have been shown to be very effective inhibitors of catamenial seizures in animal models. Thus, synthetic neuroactive steroids, such as ganaxolone, which are orally active and devoid of hormonal side effects, represent a novel treatment strategy for catamenial epilepsy. However, their clinical efficacy in catamenial epilepsy has yet to be explored. A greater understanding of the molecular mechanisms is clearly needed for designing effective treatment and prevention strategies of catamenial epilepsy in women at risk.

Neurotropic action of androgens: principles, mechanisms and novel targets

The importance of androgen signaling is well recognized for numerous aspects of central nervous system (CNS) function, ranging from sex-specific organization of neuroendocrine and behavioral circuits to adaptive capacity, resistance and repair. Nonetheless, concepts for the therapeutic use of androgens in neurological and mental disorders are far from being established. This review outlines some critical issues which interfere with decisions on the suitability of androgens as therapeutic agents for CNS conditions. Among these, sex-specific organization of neural substrates and resulting differential responsiveness to endogenous gonadal steroids, convergence of steroid hormone actions on common molecular targets, co-presence of different sex steroid receptors in target neuronal populations, and in situ biotransformation of natural androgens apparently pose the principal obstacles for the characterization of specific neurotropic effects of androgens. Additional important, albeit less explored aspects consist in insufficient knowledge about molecular targets in the CNS which are under exclusive or predominant androgen control. Own experimental data illustrate the variability of pharmacological effects of natural and synthetic androgens on CNS functions of adaptive relevance, such as sexual behavior, anxiety and endocrine responsiveness to stress. Finally, we present results from an analysis of the consequences of aging for the rat brain transcriptome and examination of the influence of androgens on differentially expressed genes with presumable significance in neuropathology.

5alpha-reduced androgens may have actions in the hippocampus to enhance cognitive performance of male rats

Androgens may improve cognitive performance; however, these effects and mechanisms of androgens are not well understood. Whether testosterone's (T) effects on cognitive performance are mediated by its 5alpha-reduced, non-aromatizable metabolite dihydrotestosterone (DHT) and/or its 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) reduced metabolite 3alpha-androstanediol (3alpha-diol), was investigated. In Experiment 1, male rats that were gonadally intact, or gonadectomized (GDX) and DHT-replaced with a silastic capsule, had better performance in the inhibitory avoidance task, and higher plasma DHT and 3alpha-diol levels, compared to GDX rats. In Experiments 2-4, intra-hippocampal indomethacin, a 3alpha-HSD inhibitor, to intact or DHT-replaced, but not GDX, rats decreased performance in the inhibitory avoidance task and reduced hippocampal 3alpha-diol levels compared to that observed in rats with control implants. Thus, the 5alpha-reduced androgen DHT has cognitive-enhancing effects, independent of E(2), which are attenuated by a 3alpha-HSD inhibitor, indomethacin. These results suggest that 5alpha-reduced androgens may have actions in the hippocampus to improve cognitive performance.

Gonadal, adrenal, and neuroactive steroids' role in ictal activity

Of the many people that have epilepsy, only about 70% achieve seizure control with traditional pharmacotherapies. Steroids have long been known to influence ictal activity and may have a therapeutic role. This review summarizes recent investigations that have enhanced knowledge of the effects and mechanisms of gonadal, adrenal, and neuroactive steroids on seizure processes. Progesterone, which varies across reproductive cycles, pregnancy, and as a function of aging, has been shown to have anti-seizure effects among women with epilepsy and in animal models of epilepsy. Further, data suggest that progesterone's anti-seizure effects may involve its metabolism to the neuroactive steroid, 5 alpha-pregnan-3 alpha-ol-20-one (3 alpha,5 alpha-THP), and its subsequent actions at GABA(A) receptors. Androgens also have anti-seizure effects. Androgens' anti-seizure effects may be mediated, in part, through actions of the testosterone metabolite, and neuroactive steroid, 5 alpha-androstane-3 alpha,17 alpha-diol (3 alpha-diol) at GABA(A) receptors. Stress can alter seizure susceptibility, suggesting a role of adrenal steroids on seizure processes. In animal models of epilepsy, acute or chronic stress can increase ictal activity. Notably, stress and seizures can alter levels of gonadal, adrenal, and neuroactive steroids, which may then influence subsequent seizure activity. Thus, this review summarizes recent progress in the role of gonadal, adrenal, and/or neuroactive steroids in seizure processes which suggest that greater understanding of these steroids' effects and mechanisms may ultimately lead to improved seizure control for people with epilepsy.