ganaxolone and Disease-Models--Animal

An increasing number of studies implicate the GABAAergic system in the pathophysiology of the fragile X syndrome, a frequent cause of intellectual disability and autism. Animal models have proven invaluable in unravelling the molecular mechanisms underlying the disorder. Multiple defects in this inhibitory system have been identified in Fmr1 knockout mice, including altered expression of various components, aberrant GABAA receptor-mediated signalling, altered GABA concentrations and anatomical defects in GABAergic neurons. Aberrations compatible with those described in the mouse model were detected in dfmr1 deficient Drosophila melanogaster, a validated fly model for the fragile X syndrome. Treatment with drugs that ameliorate the GABAAergic deficiency in both animal models have demonstrated that the GABAA receptor is a promising target for the treatment of fragile X patients. Based on these preclinical studies, clinical trials in patients have been initiated.

Topics: Animals; Brain; Clinical Trials as Topic; Disease Models, Animal; Fragile X Syndrome; GABA Modulators; Humans; Pregnanolone; Receptors, GABA-A

The functions for neurosteroids during development and in response to nervous system injury are beginning to be identified. We focused on a mouse model in which we believed neurosteroid production would be altered, and which had a neurodegenerative phenotype. Niemann-Pick Type-C (NP-C) is an autosomal recessive neurodegenerative disease caused by mutations in NPC1 (95%) or NPC2 (5%), resulting in lysosomal accumulation of unesterified cholesterol and glycolipids. The NIH mouse model of NP-C has a mutation in the NPC1 gene, and exhibits several pathological features of the most severe NP-C patients. How lysosomal storage and trafficking defects lead to neurodegeneration is unknown. We found that these mice had normal neurosteroidogenic enzyme activity during development, but lost this activity in the early neonatal period, prior to onset of neurological symptoms. Neurons that expressed P450scc, 3beta HSD, as well as those that expressed 3alpha HSD and 5alpha reductase were lost in adult NP-C brains, resulting in diminished concentrations of allopregnanolone. We treated NP-C mice with allopregnanolone and found that a single dose in the neonatal period resulted in a doubling of life span, substantial delay in onset of neurological symptoms, survival of cerebellar Purkinje and granule cell neurons, and reduction in cholesterol and ganglioside accumulation. The mechanism by which allopregnanolone elicited these effects is unknown. Our in vitro studies showed that Purkinje cell survival promoted by allopregnanolone was lost by treatment with bicuculline, suggesting GABA(A) receptors may play a role. We treated NP-C mice with a synthetic GABA(A) neurosteroid, ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one). Ganaxolone treatment of NP-C mice produced beneficial neurological effects, but these effects were not as robust as those obtained using allopregnanolone. Thus, allopregnanolone may elicit its effects through GABA(A) receptors and through other mechanisms. Additional studies also suggest that allopregnanolone may elicit its effects through pregnane-X-receptors (PXR). Our data suggest that mouse models of neurodegeneration may be beneficial in establishing both physiologic and pharmacologic actions of neurosteroids. These animal models further establish the wide range of functions of these compounds, which may ultimately be useful for treatment of human diseases.

Topics: Animals; Disease Models, Animal; Gonadal Steroid Hormones; Humans; Mice; Niemann-Pick Disease, Type C; Pregnanolone; Receptors, GABA-A

Topics: Acetamides; Amines; Animals; Anticonvulsants; Benzodiazepines; Carbamates; Cyclohexanecarboxylic Acids; Disease Models, Animal; Drug Design; Gabapentin; gamma-Aminobutyric Acid; Humans; Lacosamide; Levetiracetam; Phenylenediamines; Piracetam; Pregabalin; Pregnanolone; Pyrrolidinones; Triazoles

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.

Topics: Animals; Anticonvulsants; Brain Chemistry; Disease Models, Animal; Epilepsy; Female; Humans; Menstruation Disturbances; Models, Molecular; Pregnanolone; Progesterone; Receptors, GABA-A; Steroids

Seizures are more common in the neonatal period than at any other stage of life. Phenobarbital is the first-line treatment for neonatal seizures and is at best effective in approximately 50% of babies, but may contribute to neuronal injury. Here, we assessed the efficacy of phenobarbital versus the synthetic neurosteroid, ganaxolone, to moderate seizure activity and neuropathology in neonatal lambs exposed to perinatal asphyxia.. Asphyxia was induced via umbilical cord occlusion in term lambs at birth. Lambs were treated with ganaxolone (5mg/kg/bolus then 5mg/kg/day for 2 days) or phenobarbital (20mg/kg/bolus then 5mg/kg/day for 2 days) at 6 hours. Abnormal brain activity was classified as stereotypic evolving (SE) seizures, epileptiform discharges (EDs), and epileptiform transients (ETs) using continuous amplitude-integrated electroencephalographic recordings. At 48 hours, lambs were euthanized for brain pathology.. Asphyxia caused abnormal brain activity, including SE seizures that peaked at 18 to 20 hours, EDs, and ETs, and induced neuronal degeneration and neuroinflammation. Ganaxolone treatment was associated with an 86.4% reduction in the number of seizures compared to the asphyxia group. The total seizure duration in the asphyxia+ganaxolone group was less than the untreated asphyxia group. There was no difference in the number of SE seizures between the asphyxia and asphyxia+phenobarbital groups or duration of SE seizures. Ganaxolone treatment, but not phenobarbital, reduced neuronal degeneration within hippocampal CA1 and CA3 regions, and cortical neurons, and ganaxolone reduced neuroinflammation within the thalamus.. Ganaxolone provided better seizure control than phenobarbital in this perinatal asphyxia model and was neuroprotective for the newborn brain, affording a new therapeutic opportunity for treatment of neonatal seizures. ANN NEUROL 2022;92:1066-1079.

Topics: Animals; Animals, Newborn; Anticonvulsants; Asphyxia Neonatorum; Disease Models, Animal; Epilepsy; Humans; Infant, Newborn; Phenobarbital; Pregnanolone; Seizures; Sheep

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

Topics: Animals; Anticonvulsants; beta-Cyclodextrins; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Combinations; Drug Synergism; Drug Therapy, Combination; Hippocampus; In Vitro Techniques; Male; Membrane Potentials; Mice; Mice, Inbred C57BL; Midazolam; Neurosteroids; Patch-Clamp Techniques; Pregnanolone; Receptors, GABA-A; Seizures; Tiagabine

There is a major clinical need for new therapies for the treatment of chronic itch. Many of the molecular components involved in itch neurotransmission are known, including the neuropeptide NPPB, a transmitter required for normal itch responses to multiple pruritogens in mice. Here, we investigated the potential for a novel strategy for the treatment of itch that involves the inhibition of the NPPB receptor NPR1 (natriuretic peptide receptor 1). Because there are no available effective human NPR1 (hNPR1) antagonists, we performed a high-throughput cell-based screen and identified 15 small-molecule hNPR1 inhibitors. Using in vitro assays, we demonstrated that these compounds specifically inhibit hNPR1 and murine NPR1 (mNPR1). In vivo, NPR1 antagonism attenuated behavioral responses to both acute itch- and chronic itch-challenged mice. Together, our results suggest that inhibiting NPR1 might be an effective strategy for treating acute and chronic itch.

Topics: Animals; Behavior, Animal; Cell-Free System; Dermatitis, Contact; Disease Models, Animal; Ganglia, Spinal; Humans; Mice, Inbred C57BL; Mice, Knockout; Neurons; Pruritus; Receptors, Atrial Natriuretic Factor; Reproducibility of Results; Signal Transduction; Small Molecule Libraries

Children born preterm, especially boys, are at increased risk of developing attention deficit hyperactivity disorder (ADHD) and learning difficulties. We propose that neurosteroid-replacement therapy with ganaxolone (GNX) following preterm birth may mitigate preterm-associated neurodevelopmental impairment.. Time-mated sows were delivered preterm (d62) or at term (d69). Male preterm pups were randomized to ganaxolone (Prem-GNX; 2.5 mg/kg subcutaneously twice daily until term equivalence), or preterm control (Prem-CON). Surviving male juvenile pups underwent behavioural testing at d25-corrected postnatal age (CPNA). Brain tissue was collected at CPNA28 and mature myelinating oligodendrocytes of the hippocampus and subcortical white matter were quantified by immunostaining of myelin basic protein (MBP).. Ganaxolone treatment returned the hyperactive behavioural phenotype of preterm-born juvenile males to a term-born phenotype. Deficits in MBP immunostaining of the preterm hippocampus and subcortical white matter were also ameliorated in animals receiving ganaxolone. However, during the treatment period weight gain was poor, and pups were sedated, ultimately increasing the neonatal mortality rate.. Ganaxolone improved neurobehavioural outcomes in males suggesting that neonatal treatment may be an option for reducing preterm-associated neurodevelopmental impairment. However, dosing studies are required to reduce the burden of unwanted side effects.

Topics: Animals; Animals, Newborn; Attention Deficit Disorder with Hyperactivity; Behavior, Animal; Brain; Disease Models, Animal; GABA Modulators; Guinea Pigs; Locomotion; Male; Myelin Basic Protein; Neurosteroids; Pregnanolone; Premature Birth; Proof of Concept Study; Receptors, GABA-A; Social Behavior

Angelman syndrome (AS) is a rare neurogenetic disorder characterized by severe developmental delay, motor impairments, and epilepsy. GABAergic dysfunction is believed to contribute to many of the phenotypic deficits seen in AS. We hypothesized that restoration of inhibitory tone mediated by extrasynaptic GABA

Topics: Angelman Syndrome; Animals; Anti-Anxiety Agents; Anticonvulsants; Anxiety; Disease Models, Animal; Female; Hippocampus; Long-Term Potentiation; Male; Maze Learning; Memory, Short-Term; Mice, Knockout; Motor Activity; Pentylenetetrazole; Pregnanolone; Receptors, GABA-A; Seizures; Spatial Memory; Tissue Culture Techniques; Ubiquitin-Protein Ligases

Cicer arietinum (Chickpea) is one of the most important harvests in the world with high nutritional value. Lack of essential oils in the seeds of Chickpea is an advantage in search for drug-like molecules with less toxicity. We evaluated anticonvulsant effect of C. arietinum in common animal models of epilepsy.. Dichloromethane extract was obtained from C. arietinum seeds by percolation. Acute toxicity of the extract was assessed in mice. Protective effect of the extract was examined against tonic seizures induced by maximal electroshock (MES; 50 mA, 50 Hz, 1 s) in mice, clonic seizures induced by pentylenetetrazole (PTZ; 60 mg/kg, i.p.) in mice, and electrical kindling model of complex partial seizures in rats. The extract was fractionated by n-hexane to f1 and f2 fractions. The extract and fractions underwent phytochemical analysis by thin layer chromatography. The active anticonvulsant fraction, f1, was subjected to matrix assisted laser desorption/ionization (MALDI) mass analysis.. The crude extract had neither toxicity up to 7 g/kg nor protective activity in MES and kindling models. However, it significantly inhibited clonic seizures induced by PTZ. f1 fraction mimicked protective effect of the extract. Phytochemical screening revealed the presence of considerable amount of alkaloids in the extract and fractions. Moreover, a novel structural class was detected in f1 fraction.. Finding an anticonvulsant molecule pertaining to a new structural class in the seeds of C. arietinum promises an effective and inexpensive source of antiepileptic medication. Further studies are needed to identify its mechanism of action and more clues into its structure-activity relationship.

Topics: Animals; Anticonvulsants; Cicer; Disease Models, Animal; Electroshock; Epilepsy; Male; Mice; Pentylenetetrazole; Plant Extracts; Pregnanolone; Rats; Rats, Wistar; Seeds; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Infantile spasms (IS), a devastating epileptic encephalopathy of infancy, involve various etiologies associated with an unknown underlying common pathophysiology. The efficacy of adrenocorticotropic hormone (ACTH) as an IS therapy suggests a role for steroid hormones in treating IS. This study used an animal model of IS to test the efficacy of ganaxolone, a synthetic neurosteroid, promoting tonic GABAA inhibition.. The model of cryptogenic IS used in this study involved prenatal priming of rats with betamethasone (0.4 mg/kg i.p. at 08:30 and 18:30) on gestational day 15. To test the acute effects of ganaxolone, rats were pretreated with ganaxolone (10, 25, or 50mg/kg i.p.) or vehicle (β-cyclodextrin, i.p.) 30 min prior to N-methyl-d-aspartate (NMDA)-induced spasms at postnatal day 15 (P15). To mimic human conditions, another group of rats was randomly divided and repeatedly treated with ganaxolone (20mg/kg at 9:00 and 18:00 from P13-15) or vehicle after experiencing NMDA-triggered spasms at P12. Additional spasms were triggered on P13 and P15. We determined latency to the onset of spasms and the total number of spasms per 90-min observation period after the trigger at P15. On P19 and P21, behavioral tests were performed in rats with randomized repeated treatments.. The 25mg/kg and 50mg/kg doses of ganaxolone significantly delayed the onset of spasms compared with the controls, and significantly decreased the number of spasms or suppressed their incidence. Ganaxolone had significant side effects in terms of sedation: all animals with the 50mg/kg dose were sleeping during the test. Randomized ganaxolone treatment for 3 days also significantly delayed the onset and decreased the number of spasms triggered by NMDA on P15, and decreased exploratory behavior after multiple NMDA triggered spasms.. Ganaxolone significantly suppresses the development of spasms in the rat model of cryptogenic IS. This synthetic neurosteroid active in an animal model of IS might contribute to the current armamentarium to treat human IS.

Topics: Age Factors; Anesthetics; Animals; Animals, Newborn; Disease Models, Animal; Dose-Response Relationship, Drug; Electroencephalography; Excitatory Amino Acid Agonists; Exploratory Behavior; Female; Humans; Infant; Male; N-Methylaspartate; Pregnanolone; Rats; Rats, Sprague-Dawley; Reaction Time; Social Behavior; Spasms, Infantile; Statistics, Nonparametric

Neuroactive steroids that function as positive modulators of GABA-A receptors are potential anticonvulsant drugs. We previously demonstrated that ganaxolone is effective against pentetrazol-induced motor seizures in immature rats. In the present study, we examined the effects of ganaxolone in another model, cortical epileptic afterdischarges (ADs). The possible side effects of ganaxolone were studied in rats 12, 18, and 25 days of age following the implantation of epidural electrodes. Low-frequency stimulation of the sensorimotor cortical area elicited ADs characterized by a spike-and-wave rhythm and clonic seizures. Ganaxolone (5, 10, 20, or 40 mg/kg) was administered intraperitoneally after the first AD and stimulation was repeated five more times. The highest dose of ganaxolone (40 mg/kg) suppressed progressive prolongation of ADs in 25-day-old rats and postponed it in 12-day-old rats. No significant effect was observed in 18-day-old animals. Movements during stimulation and clonic seizures accompanying ADs were not affected by ganaxolone. Ganaxolone at doses of 20 and 40 mg/kg had no significant effect on motor function, such as surface righting, negative geotaxis, wire mesh ascending, and bar holding. After administration of 40 mg/kg ganaxolone to 18- and 25-day-old rats, spontaneous locomotion in the open field tended to decrease. Doses of ganaxolone with a moderate anticonvulsant effect in the present model did not seriously compromise motor performance.

Topics: Aging; Animals; Anticonvulsants; Brain; Disease Models, Animal; Electric Stimulation; Epilepsy; Male; Motor Activity; Neuropsychological Tests; Pregnanolone; Rats; Rats, Wistar; Seizures; Time Factors

Ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one), a synthetic analog of the endogenous neurosteroid allopregnanolone and a positive allosteric modulator of GABAA receptors, may represent a new treatment approach for epilepsy. Here we demonstrate that pretreatment with ganaxolone (1.25-20 mg/kg, s.c.) causes a dose-dependent suppression of behavioral and electrographic seizures in fully amygdala-kindled female mice, with nearly complete seizure protection at the highest dose tested. The ED50 for suppression of behavioral seizures was 6.6 mg/kg. The seizure suppression produced by ganaxolone was comparable to that of clonazepam (ED50, 0.1 mg/kg, s.c.). To the extent that amygdala kindling represents a model of mesial temporal lobe epilepsy, this study supports the utility of ganaxolone in the treatment of patients with temporal lobe seizures.

Topics: Amygdala; Animals; Anticonvulsants; Clonazepam; Disease Models, Animal; Dose-Response Relationship, Drug; Epilepsy, Temporal Lobe; Female; Kindling, Neurologic; Mice; Mice, Inbred C57BL; Pregnanolone; Seizures

Neuroactive steroids modulate ethanol intake in several self-administration models with variable effects. The purpose of this work was to examine the effects of the long-acting synthetic GABAergic neurosteroid ganaxolone and the endogenous neurosteroid pregnenolone, a precursor of all GABAergic neuroactive steroids, on the maintenance of ethanol self-administration in an animal model of elevated drinking-the alcohol-preferring (P) rats.. P rats were trained to self-administer ethanol (15% v/v) versus water on a concurrent schedule of reinforcement, and the effects of ganaxolone (0 to 30 mg/kg, subcutaneous [SC]) and pregnenolone (0 to 75 mg/kg, intraperitoneal [IP]) were evaluated on the maintenance of ethanol self-administration. After completion of self-administration testing, doses of the neuroactive steroids that altered ethanol self-administration were assessed on spontaneous locomotor activity. Finally, the effect of pregnenolone administration on cerebral cortical levels of the GABAergic neuroactive steroid (3α,5α)-3-hydroxypregnan-20-one (allopregnanolone, 3α,5α-THP) was determined in both ethanol-experienced and ethanol-inexperienced P rats because pregnenolone is a precursor of these steroids.. Ganaxolone produced a dose-dependent biphasic effect on ethanol reinforcement, as the lowest dose (1 mg/kg) increased and the highest dose (30 mg/kg) decreased ethanol-reinforced responding. However, the highest ganaxolone dose also produced a nonspecific reduction in locomotor activity. Pregnenolone treatment significantly reduced ethanol self-administration (50 and 75 mg/kg), without altering locomotor activity. Pregnenolone (50 mg/kg) produced a significant increase in cerebral cortical allopregnanolone levels. This increase was observed in the self-administration trained animals, but not in ethanol-naïve P rats.. These results indicate that pregnenolone dose-dependently reduces operant ethanol self-administration in P rats without locomotor impairment, suggesting that it may have potential as a novel therapeutic for reducing chronic alcohol drinking in individuals that abuse alcohol.

Topics: Alcoholism; Animals; Cerebral Cortex; Conditioning, Operant; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Ethanol; Male; Motor Activity; Pregnanolone; Pregnenolone; Rats; Rats, Inbred Strains; Self Administration

Neurosteroids are synthesized in the brain and have been demonstrated to modulate various cerebral functions. Allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one), a naturally occurring neurosteroid, and ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one), a synthetic derivative, are two neurosteroids acting as positive allosteric modulators of the GABA(A) receptor complex acting on a specific steroid recognition site. Both agents antagonize generalized tonic-clonic seizures in various animal models of epilepsy. Pregnenolone sulphate (3beta-hydroxy-5alpha-pregnen-20-one 3-sulphate; PS) is a negative allosteric modulator of GABA(A) receptors and a positive modulator of the NMDA receptors. We have evaluated the effects of such compounds in a genetic animal model of absence epilepsy, the WAG/Rij rat. Animals were chronically implanted with five frontoparietal cortical electrodes for electrocorticogram (EEG) recordings and bilateral guide cannulae into specific brain areas of the cortico-thalamic circuit in order to evaluate the effects of these compounds on the number and duration of epileptic spike-wave discharges (SWDs). The focal and bilateral microinjection of the two GABA(A) positive modulators into some thalamic nuclei (nucleus ventralis posteromedialis, nucleus reticularis thalami, nucleus ventralis posterolateralis was usually able to significantly worsen the occurrence of SWDs in WAG/Rij rats. Whereas both compounds were able to reduce the number and duration of SWDs when microinjected into the peri-oral region of the primary somatosensory cortex. The effects of PS were more complex depending on both the dose and the site of administration, generally, at low doses in thalamic nuclei and cortex, PS induced an increase of absence activity and a reduction at higher doses. These findings suggest that neurosteroids might play a role in absence epilepsies and that it might depend on the involvement of specific neuronal areas.

Topics: Animals; Behavior, Animal; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Electroencephalography; Epilepsy, Absence; Male; Microinjections; Pregnanolone; Pregnenolone; Rats; Rats, Inbred Strains; Time Factors

Low-frequency (6 Hz), long-duration (3 s) electrical stimulation in mice produces seizures characterized by immobility, focal clonus, and automatic behaviors reminiscent of human limbic epilepsy. Renewed interest has been expressed in this seizure model with the recognition that it is sensitive to a broad spectrum of anticonvulsants (AEDs) and may have distinct pharmacologic responsiveness from other in vivo tests of AED efficacy. Here we sought to determine whether the progesterone-derived neuroactive steroid allopregnanolone (5alpha,3alpha-P) and several structural analogues with varying degrees of activity as positive allosteric modulators of gamma-aminobutyric acid (GABA)A receptors are protective in the 6-Hz seizure model.. Mice were pretreated with neuroactive steroids (15 min before) or clonazepam (CZP; 30 min before) to 6-Hz corneal stimulation (32 mA). Animals that failed to exhibit immobility were considered protected.. The neuroactive steroids prevented 6-Hz seizures with rank order of potencies (ED50 values): ganaxolone (6.3 mg/kg) > 5alpha,3alpha-P (14.2 mg/kg) > or = 5beta,3alpha-P (14.4 mg/kg) > 5alpha,3beta-P (>100 mg/kg). CZP also was protective (ED(50) value, 0.075 mg/kg). The potencies of the neuroactive steroids and CZP are similar to their previously reported activities in the pentylenetetrazol (PTZ) seizure model.. Neuroactive steroids have comparable potencies in the 6-Hz and PTZ models. Their structural specificity in both models corresponds with their activities as positive allosteric modulators of GABAA receptors, although ganaxolone is more potent than expected, probably because it has greater bioavailability. The 6-Hz model may be a valuable tool in drug development for the identification of GABAergic AEDs.

Topics: Animals; Anticonvulsants; Clonazepam; Cornea; Disease Models, Animal; Dose-Response Relationship, Drug; Electric Stimulation; Epilepsies, Partial; GABA Modulators; Humans; Male; Mice; Pregnanolone; Receptors, GABA; Seizures; Steroids

To determine the effects of a newly synthesized epalon, ganaxolone (GNX), on primarily generalized seizures in rats of various ages during development. Epalons are classified as neuroactive steroids that interact at unique site of the GABAA receptor-Cl- channel complex in the central nervous system.. Sprague-Dawley male rats were used at 9, 15, 30, and 60 postnatal days (PN). GNX dissolved in 2-hydroxypropylbeta-cyclodextrine was administered intraperitoneally in different doses at various time points before flurothyl testing. The incidence and threshold of clonic and tonic-clonic flurothyl seizures were evaluated. Behavioral changes were also assessed.. In all age groups, the effects of GNX were dose dependent and more prominent 10 min after its administration. In PN 60 and PN 30 rats, GNX had dose-dependent anticonvulsant effects; tonic-clonic seizures were more sensitive to GNX treatment than clonic seizures. In PN 15 and PN 9 rats, GNX demonstrated dose-and time-dependent anticonvulsant effects against both types of flurothyl-induced seizures. GNX was more effective in PN 15 rats than in other age groups, but at doses that altered motor behavior.. GNX has anticonvulsant effects against flurothylinduced seizures in all age groups tested. Its effects are more prominent in the two younger age groups, especially in PN 15 rats, but are associated with motor side effects.

Topics: Age Factors; Animals; Animals, Newborn; Anticonvulsants; Behavior, Animal; Disease Models, Animal; Dose-Response Relationship, Drug; Epilepsy, Tonic-Clonic; Flurothyl; Male; Motor Activity; Pregnanolone; Rats; Rats, Sprague-Dawley; Seizures

Perimenstrual catamenial epilepsy, the exacerbation of seizures in association with menstruation, may in part be due to withdrawal of the progesterone metabolite allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one), an endogenous anticonvulsant neurosteroid that is a positive allosteric modulator of gamma-aminobutyric acid(A) receptors. Neurosteroid replacement is a potential approach to therapy, but natural neurosteroids have poor bioavailability and may be converted to metabolites with undesired progestational activity. The synthetic neuroactive steroid ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnane-20-one) is an orally active analog of allopregnanolone that is not converted to the hormonally active 3-keto form. To assess the potential of ganaxolone in the treatment of catamenial seizure exacerbations, a state of persistently high serum progesterone (pseudopregnancy) was induced in 26-day-old female rats with gonadotropins, and neurosteroids were withdrawn on postnatal day 39 with finasteride, a 5alpha-reductase inhibitor that blocks the conversion of progesterone to allopregnanolone. Finasteride treatment during pseudopregnancy results in a reduction in the threshold for pentylenetetrazol seizures. During this state of enhanced seizure susceptibility, there was a 3-fold increase in the anticonvulsant potency of ganaxolone (control ED(50) = 3.5 mg/kg; withdrawn = 1.2 mg/kg) without a change in the potency for induction of motor toxicity in the rotarod test. The plasma concentrations of ganaxolone did not differ significantly in control and withdrawn animals; the estimated plasma concentrations of ganaxolone producing 50% seizure protection were approximately 500 and approximately 225 ng/ml in control and withdrawn rats, respectively. Unlike ganaxolone, neurosteroid withdrawal was associated with a decrease in the anticonvulsant potency of diazepam (control ED(50) = 1.9 mg/kg; withdrawn = 4.1 mg/kg) and valproate (control ED(50) = 279 mg/kg; withdrawn = 460 mg/kg). The enhanced anticonvulsant potency of ganaxolone after neurosteroid withdrawal supports the use of ganaxolone as a specific treatment for perimenstrual catamenial epilepsy.

Topics: Animals; Anticonvulsants; Convulsants; Diazepam; Disease Models, Animal; Enzyme Inhibitors; Epilepsy; Female; Finasteride; Menstruation; Oxidoreductases; Pentylenetetrazole; Pregnanolone; Pseudopregnancy; Rats; Rats, Sprague-Dawley; Seizures; Steroids; Valproic Acid