3alpha,5alpha-THP in the raphe magnus attenuates PTZ-induced myoclonic seizures

The diverse role of the raphe 5-HTergic systems in epilepsy

The raphe nuclei comprise nearly all of 5-hydroxytryptaminergic (5-HTergic) neurons in the brain and are widely acknowledged to participate in the modulation of neural excitability. "Excitability-inhibition imbalance" results in a variety of brain disorders, including epilepsy. Epilepsy is a common neurological disorder characterized by hypersynchronous epileptic seizures accompanied by many psychological, social, cognitive consequences. Current antiepileptic drugs and other therapeutics are not ideal to control epilepsy and its comorbidities. Cumulative evidence suggests that the raphe nuclei and 5-HTergic system play an important role in epilepsy and epilepsy-associated comorbidities. Seizure activities propagate to the raphe nuclei and induce various alterations in different subregions of the raphe nuclei at the cellular and molecular levels. Intervention of the activity of raphe nuclei and raphe 5-HTergic system with pharmacological or genetic approaches, deep brain stimulation or optogenetics produces indeed diverse and even contradictory effects on seizure and epilepsy-associated comorbidities in different epilepsy models. Nevertheless, there are still many open questions left, especially regarding to the relationship between 5-HTergic neural circuit and epilepsy. Understanding of 5-HTergic network in a circuit- and molecule-specific way may not only be therapeutically relevant for increasing the drug specificity and precise treatment in epilepsy, but also provide critical hints for other brain disorders with abnormal neural excitability. In this review we focus on the roles of the raphe 5-HTergic system in epilepsy and epilepsy-associated comorbidities. Besides, further perspectives about the complexity and diversity of the raphe nuclei in epilepsy are also addressed.

Syntaxin 1B Mediates Berberine's Roles in Epilepsy-Like Behavior in a Pentylenetetrazole-Induced Seizure Zebrafish Model

Epilepsy is a neuronal dysfunction syndrome characterized by transient and diffusely abnormal discharges of neurons in the brain. Previous studies have shown that mutations in the syntaxin 1b (stx1b) gene cause a familial, fever-associated epilepsy syndrome. It is unclear as to whether the stx1b gene also correlates with other stimulations such as flashing and/or mediates the effects of antiepileptic drugs. In this study, we found that the expression of stx1b was present mainly in the brain and was negatively correlated with seizures in a pentylenetetrazole (PTZ)-induced seizure zebrafish model. The transcription of stx1b was inhibited by PTZ but rescued by valproate, a broad-spectrum epilepsy treatment drug. In the PTZ-seizure zebrafish model, stx1b knockdown aggravated larvae hyperexcitatory swimming and prompted abnormal trajectory movements, particularly under lighting stimulation; at the same time, the expression levels of the neuronal activity marker gene c-fos increased significantly in the brain. In contrast, stx1b overexpression attenuated seizures and decreased c-fos expression levels following PTZ-induced seizures in larvae. Thus, we speculated that a deficiency of stx1b gene expression may be related with the onset occurrence of clinical seizures, particularly photosensitive seizures. In addition, we found that berberine (BBR) reduced larvae hyperexcitatory locomotion and abnormal movement trajectory in a concentration-dependent manner, slowed down excessive photosensitive seizure-like swimming, and assisted in the recovery of the expression levels of STX1B. Under the downregulation of STX1B, BBR's roles were limited: specifically, it only slightly regulated the levels of the two genes stx1b and c-fos and the hyperexcitatory motion of zebrafish in dark conditions and had no effect on the overexcited swimming behavior seen in conjunction with lighting stimulation. These findings further demonstrate that STX1B protein levels are negatively correlated with a seizure and can decrease the sensitivity of the photosensitive response in a PTZ-induced seizure zebrafish larvae; furthermore, STX1B may partially mediate the anticonvulsant effect of BBR. Additional investigation regarding the relationship between STX1B, BBR, and seizures could provide new cues for the development of novel anticonvulsant drugs.

Progesterone's role in neuroprotection, a review of the evidence

The sex hormone progesterone has been shown to improve outcomes in animal models of a number of neurologic diseases, including traumatic brain injury, ischemia, spinal cord injury, peripheral nerve injury, demyelinating disease, neuromuscular disorders, and seizures. Evidence suggests it exerts its neuroprotective effects through several pathways, including reducing edema, improving neuronal survival, and modulating inflammation and apoptosis. In this review, we summarize the functional outcomes and pathophysiologic mechanisms attributed to progesterone treatment in neurologic disease. We then comment on the breadth of evidence for the use of progesterone in each neurologic disease family. Finally, we provide support for further human studies using progesterone to treat several neurologic diseases.

Progesterone attenuates depressive behavior of younger and older adult C57/BL6, wildtype, and progesterone receptor knockout mice

Progesterone may have actions independent of intracellular progestin receptors (PRs) to influence depressive behavior. To investigate this, we examined effects of progesterone (P; 10mg/kg, SC) on the depressive behavior of mice in the forced swim test (FST). In Experiment 1, subjects were 4 to 6 months old, intact or ovariectomized (OVX) female and intact or gonadectomized (GDX) male, C57/BL6 mice. Progesterone reduced depressive behavior of young diestrous and OVX mice but male mice were impervious to effects of P. In Experiment 2, subjects were intact aged (20-28 months old) C57/BL6 female and male mice. Progesterone reduced depressive behavior of aged female and male C57/BL6 mice, albeit effects were greater among males. In Experiment 3, effects of P were examined in 4 to 6 months old, gonadally-intact, female and male mice that were wildtype or PR knockouts (PRKOs). Progesterone decreased depressive behavior of young adult, wildtype and PRKO mice, which showed greater immobility than did their wildtype counterparts. In Experiment 4, subjects were 18-24 months old wildtype or PRKO mice (Exp 4). Progesterone decreased immobility among wildtype and PRKO mice (which were not different in terms of their baseline depressive behavior). Together these data demonstrate that P decreases depressive behavior of young and older adult C57/BL6, wildtype and PRKO mice, which suggest that acute anti-depressant effects of P may occur independent of actions at "classic" PRs.

Effects of antiepileptics on behavioral and electroencephalographic seizure induced by pentetrazol in mice

The present study was undertaken to investigate changes of the electroencephalogram (EEG) induced by pentetrazol (PTZ) in comparison with behavioral seizures in mice. Under pentobarbital anesthesia, mice were fixed to a stereotaxic apparatus, and electrodes were implanted into the frontal and occipital cortex. Behavioral and EEG changes were observed for 30 min following PTZ administration. After PTZ administration, mice showed myoclonic seizure (MCL) and clonic seizure (CL) in order. At the same time, spiking activity and spike-wave discharge in the cortex were observed. Phenobarbital, sodium valproate, diazepam, ethosuximide, and gabapentin caused a dose-dependent shortening of the duration of MCL and CL. In addition, they shortened the duration of spiking activity and spike-wave discharge dose-dependently. Moreover, phenytoin significantly inhibited the duration of spiking activity. It can be concluded that PTZ-induced spiking activity and spike-wave discharge serve as useful indices to assess the potential of antiepileptic activity in absence and MCLs in humans. Moreover, it is supposed that employing an index of EEG activity in addition to that of behavioral activity is desirable for objectivity.

Effects of progesterone administration and APPswe+PSEN1Deltae9 mutation for cognitive performance of mid-aged mice

Progesterone (P(4)) and its metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) have trophic effects and may improve cognitive function. We investigated the role of progestins in a murine model of Alzheimer's Disease (AD) in which transgenic mice co-overexpress a mutant form of amyloid precursor protein (APPswe) and a deletion in presenilin 1 Delta exon 9 (APPswe+PSEN1Deltae9). We hypothesized that: (1) mice with the APPswe+PSEN1Deltae9 mutation would have performance deficits compared to wildtype mice and (2) long-term administration of P(4) would enhance cognitive performance and increase brain progestin levels over placebo. Mice were ovariectomized at 6 months of age and administered placebo or P(4) via subcutaneously implanted pellets. Mice were tested between 9 and 12 months of age for cognitive performance in the object placement, water maze, object recognition, and T-maze tasks and for motor behavior in an activity monitor and then tissues were collected for steroid measurement. P(4) administration increased progestin levels in cortex, diencephalon, midbrain, and cerebellum of wildtype and mutant mice, but increases in 3alpha,5alpha-THP levels in the hippocampus of APPswe+PSEN1Deltae9 mutant mice were attenuated compared to that observed in wildtype mice. APPswe+PSEN1Deltae9 mice showed poorer performance in hippocampus measures (object placement and water maze tasks). In the object recognition and T-maze task, which are mediated by the cortex and hippocampus, P(4) administration improved performance in both wildtype and APPswe+PSEN1Deltae9 mutant mice compared to placebo administration. Thus, APPswe+PSEN1Delta9 mice have deficits in hippocampal performance and capacity to form 3alpha,5alpha-THP in the hippocampus and both wildtype and APPswe+PSEN1Delta9 mice show beneficial effects of P(4) in cortical function and similar capacity to form 3alpha,5alpha-THP in the cortex.

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.

3alpha,5alpha-THP mediates progestins' effects to protect against adrenalectomy-induced cell death in the dentate gyrus of female and male rats

Progestins have neuroprotective effects in several in vitro models of neurodegeneration and in vivo in seizure models. The extent to which progesterone's in vivo protective effects may generalize to models not involving seizure processes and whether progesterone's protective effects are modulated by its metabolites have not been comprehensively investigated. The present experiments investigated the effects of progesterone and its metabolites, dihydryoprogesterone (DHP) and 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), to protect the hippocampus from damage induced by adrenalectomy (ADX). In Experiments 1 and 2, progesterone, DHP, or 3alpha,5alpha-THP administration (1 mg/kg sc) to female (Experiment 1) or male (Experiment 2) rats similarly reduced the total number of ADX-induced pyknotic cells in the dentate gyrus compared with vehicle administration. In Experiment 3, blocking progesterone's metabolism to 3alpha,5alpha-THP with coadministration of a 5alpha-reductase inhibitor, finasteride (10 mg/kg sc), in female rats attenuated progesterone's protective effects on cell death in the dentate gyrus. Together, these data suggest that progestins can protect against ADX-induced cell death and that the actions of the progesterone metabolite, 3alpha,5alpha-THP, may underlie these effects.

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.

Inter-ictal and post-ictal circulating levels of allopregnanolone, an anticonvulsant metabolite of progesterone, in epileptic children

Allopregnanolone belongs to a group of neuroactive steroid hormones, or neurosteroids, synthesized and acting within the brain and is as a potent endogenous positive modulator of GABA(A) receptor complex. Administration of allopregnanolone protects rats against pentylentetrazol, bicuculline, kainic acid, and picrotoxin-induced seizures. We investigated serum allopregnanolone levels in children with active epilepsy at pubertal Tanner's stage I (n=52). Blood specimens were collected at least 12 h after a seizure (inter-ictal). In a subgroup of patients (n=11), specimens were also collected within 30 min from a seizure attack (post-ictal). Healthy age-matched children (n=18) served as controls. Serum allopregnanolone was measured by radioimmunoassay using a polyclonal antiserum. The inter-ictal serum allopregnanolone levels in the epileptic children were not statistically different from those detected in the control group, whereas post-ictal levels were significantly higher than the inter-ictal ones (P=0.0001). In this subgroup of patients allopregnanolone levels decreased to the basal values during the following 12 h. Serum allopregnanolone levels may therefore reflect changes in neuronal excitability, and allopregnanolone appears to be a reliable circulating marker of epileptic seizures. It is possible that increased post-ictal serum levels of allopregnanolone may play a role in modulating neuronal excitability and may represent an endogenous mechanism of seizure control.