Selective AMPA Receptor Antagonist Research Articles

Deciphering the Biophysical Properties of Ion Channel Gating Pores by Coumarin–Benzodiazepine Hybrid Derivatives: Selective AMPA Receptor Antagonists

Deciphering the Biophysical Properties of Ion Channel Gating Pores by Coumarin–Benzodiazepine Hybrid Derivatives: Selective AMPA Receptor Antagonists

IRAS/Nischarin modulates morphine reward by glutamate receptor activation in the nucleus accumbens of mouse brain

The I1 imidazoline receptor and its candidate protein imidazoline receptor antisera-selected (IRAS)/Nischarin are linked to μ opioid receptor (MOR) functions associated with MOR trafficking. We previously demonstrated that IRAS may play an important role in the development of morphine tolerance and physical dependence in vivo. However, the effects of IRAS on morphine psychological dependence are not fully understood. To extend these studies, we investigated the impact of IRAS on morphine dependence in conditioned place preference (CPP) experiments and explored the underlying mechanisms. Knockout of IRAS enhanced the acquisition and reinstatement of morphine-induced CPP. Conditional-knockout of IRAS in the nucleus accumbens (NAc) reproduced higher CPP, and overexpression of IRAS in the NAc rescued the increased morphine-induced CPP in IRAS-/- mice. IRAS-/- mice showed dramatic cAMP-dependent protein kinase (PKA) activation, upregulation of the phosphorylation of the AMPA receptor GluR1-S845 and NMDA receptor NR1-S897 in the NAc after CPP experiment. Moreover, knockout of IRAS induced an increase in spontaneous excitatory postsynaptic current (sEPSC) frequency and a decrease in the AMPA/NMDA ratio in the NAc after chronic morphine treatment. The selective AMPA receptor antagonist NBQX could inhibit morphine CPP in WT mice, while its effect was significantly reduced in IRAS-/- mice. Together, our results demonstrate that IRAS contributes to the regulation of morphine dependence and that the alteration of glutamatergic transmission in the NAc may participate in the effect of IRAS.

Search for Selective Glua1 Ampa Receptor Antagonists in a Series of Dicationic Compounds

Search for Selective Glua1 Ampa Receptor Antagonists in a Series of Dicationic Compounds

Effectiveness and tolerability of perampanel in сhildren and adolescents (own experience of Svt. Luka’s Institute of Child Neurology and Epilepsy)

Despite the significant advances in epileptology, including various new effective treatments for drug-resistant epilepsy in children, there is still a relatively large proportion of patients ineligible for surgery and alternative treatments (such as vagus nerve stimulation and ketogenic diet). Drug-resistant epilepsy accounts for approximately 30 % of all forms of epilepsy and is particularly common among patients with focal seizures. The search for new antiepileptic drugs (AEDs) is critical for these patients. Perampanel (Fycompa®, Eisai) is a novel AED that employs a fundamentally different mechanism of action compared to existing AEDs. Perampanel is a powerful highly selective non-competitive postsynaptic AMPA receptor antagonist acting at the level of neocortex and in the hippocampus. Phase III clinical trials demonstrated its high efficacy and good tolerability in patients with drug-resistant focal seizures. Randomized placebo-controlled trials assessing the efficacy of perampanel as add-on therapy showed that perampanel at a dose of 4–12 mg/day significantly reduced the frequency of focal seizures in patients with drug-resistant epilepsy along with a good safety and tolerability profile. Open-label observational studies and studies analyzing long-term therapy also demonstrated high efficacy and safety of long-term treatment with perampanel (up to 3 years), as well as good retention rate. The drug has a once-daily dosing schedule, which is very comfortable for patients. In 2012, perampanel (Fycompa®) was approved for epilepsy patients in the USA and Europe. In 2013, it was approved in Russia as an add-on therapy for patients aged 12 years and older with focal and secondary generalized seizures. On 29.06.2015, it was also approved for polytherapy of generalized tonic-clonic seizures in patients aged 12 years and older with idiopathic generalized epilepsy. On 07.12.2020, perampanel was approved for children aged 4 years and older (body weight >30 kg) as a part of polytherapy for focal and secondary generalized seizures and for children aged 7 years and older with idiopathic generalized epilepsy as a part of polytherapy for generalized tonic-clonic seizures. Currently, there is limited evidence of perampanel efficacy in children in Russia. The study aimed to evaluate the efficacy and tolerability of perampanel in children (aged 4–11 years) and adolescents (aged 12–18 years) with epilepsy treated and followed-up at Svt. Luka’s Institute of Child Neurology and Epilepsy. Materials and methods . This study included 136 patients (aged 4–18 years; 75 males and 61 females) who received perampanel and were followed-up for at least 6 months at our institution. Patients were divided into two groups: children (aged 4–11 years; n = 105) and adolescents (aged 12–18 years; n = 31). The following types of epilepsy were diagnosed in study participants: structural focal epilepsy (n = 60), genetic epilepsy (n = 61; including Dravet syndrome, Angelman syndrome, Lafora disease, mutations in the PCDH19, PHACTR1, CDKL5, ARX, PING, SCN2A, KIAA2022 genes, chromosome microdeletions, etc.), focal epilepsy of unknown etiology (n = 12), idiopathic epilepsy (n = 3). In all cases, perampanel was used as an additional AED, often in combination with valproic acid. Dose adjustment was performed according to the package insert (by increments of 2 mg either weekly or every 2 weeks) up to a therapeutic dose of 4–12 mg/day at bedtime. Results . In children (aged 4–11 years; n = 105), seizure remission was achieved in 29 cases (27.6 %). Fifty-five children (52.4 %) had ≥50 % efficacy, whereas 17 children (16.2 %) had <50 % reduction in seizure frequency or no effect. Four patients (3.4 %) reported aggravation of seizures. A significant therapeutic effect (remission or at least 50 % reduction in seizure frequency) was registered in 84 out of 105 patients (80 %). Parents of 23 children also reported better development and improved skill acquisition along with a reduced frequency of seizures (in 34 % of 67 children with cognitive disorders). Parents of 8 children who had sleeping difficulties (trouble falling asleep, restless sleep, frequent awakenings) reported an improvement of sleep. Among adolescents (n = 31), we observed the following parameters of treatment efficacy: 9 of them (29 %) achieved seizure remission; 15 patients (48.4%) had 50 % efficacy; 6 patients (19.4 %) had <50 % reduction in seizure frequency or no effect; one patient (3.2 %) had seizure aggravation. Thus, good therapeutic effect (remission or at least 50 % reduction in seizure frequency) was achieved in 24 out of 31 patients (77 %). Therapy with perampanel was effective (remission or at least 50 % reduction in seizure frequency) in 108 out of 136 patients aged 4–18 years (79.4 %). The overall seizure remission rate reached 27.9 % (38 out of 136 patients). The inclusion of perampanel into polytherapy resulted in suppression of epileptiform activity on the electroencephalogram (EEG) or in a significantly reduced index of epileptiform activity in 38 out of 112 patients who underwent followup EEG examination (i.e. in more than one-third of cases). Adverse events were registered in 41 patients out of 136 (30.1 %). Perampanel was discontinued in 15 out of 136 patients (11 %) due to tolerability issues primarily because of psychiatric adverse events (5.9 % from the total number of patients). The 12-month retention rate in children and adolescents was 78.7 % (107 out of 136 patients). Conclusion . Perampanel was highly effective in children and adolescents with genetic and structural focal epilepsy. The drug has a convenient once-daily dosing schedule with slow titration and is well tolerated by patients during longterm therapy. Our results demonstrate that perampanel is also effective in children below 12 years of age, even at a dose of 2–4 mg/day; it is well tolerated and is comfortable for use. Its efficacy and tolerability did not differ significantly between children and adolescents. Our findings suggest that perampanel is highly effective in patients with some forms of genetic epilepsy. Perampanel should be used not only for drug-resistant epilepsy, but also as the first additional drug in combination therapy for epilepsy, since it is likely to improve treatment efficacy and ensure better tolerability.

Treatment of epilepsy associated with primary and metastatic brain tumors

There is a number of unsolved issues in management of epilepsy associated with primary and metastatic brain tumors (BTs). In particular, no consensus approaches to treatment of patients with epilepsy associated with BTs have been proposed regarding use of current anti-epileptic drugs (AEDs). The review presents the relevant data on epidemiology, features of clinically manifested epilepsy at varying stages of BTs, aspects of drug-drug interaction between AEDs and anti-tumor agents, AED-related effects on cognitive functions as well as quality of life in patients with epilepsy associated with BTs. Levetiracetam and valproic acid comprise the first-line drugs for treating seizures in patients with BTs. It is unreasonable to use AEDs acting as hepatic microsomal enzyme inducers for therapy of epileptic seizures in BTs, because it may decrease efficacy of chemotherapy agents and glucocorticoids along with elevated rate of side effects. Perampanel acting as a selective noncompetitive AMPA receptor antagonist, may be one of the drugs of choice for the adjunctive therapy of epileptic seizures associated with BTs.

Treatment of pharmacoresistant sleep-related hypermotor epilepsy (SHE) with the selective AMPA receptor antagonist perampanel

This study aimed to evaluate the efficacy and tolerability of perampanel (PER) as adjunctive therapy in patients with pharmacoresistant sleep-related hypermotor epilepsy (SHE). Patients diagnosed with SHE who received PER treatment between 2016 and 2019 were included, and their data were reviewed retrospectively. Diagnosis was based on reports of patients or family members witnessing the events and clinical characteristics of seizures captured by video or during video-electroencephalography monitoring. Among 36 SHE patients, 20 with pharmacoresistant SHE (six female; mean age: 34.1 ± 9.0 years) who received PER as adjunctive therapy were included in this study. Fourteen out of the 20 patients received PER with mean length of PER exposure of 24.6 ± 15.7 months: 10 of them were responders and four non-responders. The remaining six patients discontinued PER for adverse events (n = 5) and patient choice (n = 1). Among the 10 responders, six (60%) reported seizure-free periods lasting ≥6 months. The most common PER-associated adverse event was dizziness (25%) followed by malaise (10%). Clinical experience with these patients demonstrated that PER might be considered as an add-on anti-seizure medication for patients with highly pharmacoresistant SHE.

P2X7 receptors exert a permissive effect on the activation of presynaptic AMPA receptors in rat trigeminal caudal nucleus glutamatergic nerve terminals

BackgroundPurine receptors play roles in peripheral and central sensitization and are associated with migraine headache. We investigated the possibility that ATP plays a permissive role in the activation of AMPA receptors thus inducing Glu release from nerve terminals isolated from the rat trigeminal caudal nucleus (TCN).MethodsNerve endings isolated from the rat TCN were loaded with [3H]D-aspartic acid ([3H]D-ASP), layered into thermostated superfusion chambers, and perfused continuously with physiological medium, alone or with various test drugs. Radioactivity was measured to assess [3H]D-ASP release under different experimental conditions.ResultsSynaptosomal [3H]D-ASP spontaneous release was stimulated by ATP and to an even greater extent by the ATP analogue benzoylbenzoylATP (BzATP). The stimulation of [3H]D-ASP basal release by the purinergic agonists was prevented by the selective P2X7 receptor antagonist A438079. AMPA had no effect on basal [3H]D-ASP release, but the release observed when synaptosomes were exposed to AMPA plus a purinoceptor agonist exceeded that observed with ATP or BzATP alone. The selective AMPA receptor antagonist NBQX blocked this “excess” release. Co-exposure to AMPA and BzATP, each at a concentration with no release-stimulating effects, evoked a significant increase in [3H]D-ASP basal release, which was prevented by exposure to a selective AMPA antagonist.ConclusionsP2X7 receptors expressed on glutamatergic nerve terminals in the rat TCN can mediate Glu release directly and indirectly by facilitating the activation of presynaptic AMPA receptors. The high level of glial ATP that occurs during chronic pain states can promote widespread release of Glu as well as can increase the function of AMPA receptors. In this manner, ATP contributes to the AMPA receptor activation involved in the onset and maintenance of the central sensitization associated with chronic pain.

Modulation of AMPA Receptor Gating by the Anticonvulsant Drug, Perampanel.

Postsynaptic AMPA/glutamate receptors, essential for neuronal excitability, are important targets for anticonvulsant therapy. This single channel study of the selective noncompetitive AMPA receptor antagonist, perampanel, was performed on homotetrameric GluA3 receptor-channels that open in a stepwise manner to four distinct conductance levels through independent subunit activation. Previous structural studies show that perampanel binds to four sites located within the extracellular/transmembrane boundary of closed AMPA receptor-channel subunits. We found that channels exposed to 1 or 2 μM perampanel opened mainly to the two lower conductance levels in a dose-dependent manner. Comparison of the single channel results in the structures of the full length AMPA receptor in the closed state bound to perampanel, and the open state provide insights into the mechanism of allosteric reduction of AMPA-receptor-mediated excitation in epilepsy.

Spinal Protein Kinase Mζ Regulates α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid Receptor Trafficking and Dendritic Spine Plasticity via Kalirin-7 in the Pathogenesis of Remifentanil-induced Postincisional Hyperalgesia in Rats.

Intraoperative remifentanil anesthesia exaggerates postoperative pain sensitivity. Recent studies recapitulate the significance of protein kinase Mζ in α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated pathologic pain. Kalirin-7, a Rho guanine nucleotide exchange factor, coordinates AMPA receptor trafficking and dendritic spine plasticity. This study examines whether protein kinase Mζ and Kalirin-7 contribute to remifentanil-induced postincisional hyperalgesia via AMPA receptor. Plantar incision was performed 10 min after the start of remifentanil infusion (1 µg · kg · min for 60 min). Paw withdrawal threshold (primary outcome), spinal protein kinase Mζ activity, Kalirin-7 expression, AMPA receptor trafficking, and spine morphology were assessed. Protein kinase Mζ inhibitor and Kalirin-7 knockdown by short hairpin RNA elucidated the mechanism and prevention of hyperalgesia. Whole-cell patch-clamp recording analyzed the role of protein kinase Mζ in spinal AMPA receptor-induced current. Remifentanil reduced postincisional paw withdrawal threshold (mean ± SD, control vs. hyperalgesia, 18.9 ± 1.6 vs. 5.3 ± 1.2 g, n = 7) at postoperative 48 h, which was accompanied by an increase in spinal protein kinase Mζ phosphorylation (97.8 ± 25.1 vs. 181.5 ± 18.3%, n = 4), Kalirin-7 production (101.9 ± 29.1 vs. 371.2 ± 59.1%, n = 4), and number of spines/10 µm (2.0 ± 0.3 vs. 13.0 ± 1.6, n = 4). Protein kinase Mζ inhibitor reduced remifentanil-induced hyperalgesia, Kalirin-7 expression, and GluA1 trafficking. Incubation with protein kinase Mζ inhibitor reversed remifentanil-enhanced AMPA receptor-induced current in dorsal horn neurons. Kalirin-7 deficiency impaired remifentanil-caused hyperalgesia, postsynaptic GluA1 insertion, and spine plasticity. Selective GluA2-lacking AMPA receptor antagonist prevented hyperalgesia in a dose-dependent manner. Spinal protein kinase Mζ regulation of GluA1-containing AMPA receptor trafficking and spine morphology via Kalirin-7 overexpression is a fundamental pathogenesis of remifentanil-induced hyperalgesia in rats.

Perampanel, an AMPA receptor antagonist: From clinical research to practice in clinical settings.

Epileptic seizures are refractory to treatment in approximately one-third of patients despite the recent introduction of many newer antiepileptic drugs (AEDs). Development of novel AEDs therefore remains a high priority. Perampanel is a first-in-class non-competitive selective AMPA receptor antagonist with a unique mechanism of action. Clinical efficacy and safety of perampanel as adjunctive treatment for focal seizures with/without secondary generalization (±SG) and primary generalized tonic-clonic (PGTC) seizures have been established in five phase 3 randomized controlled trials (RCTs), and a long-term extension study, and perampanel is approved as monotherapy for focal seizures ±SG in the USA. In patients with focal seizures ±SG, add-on perampanel resulted in median percent reduction in seizure frequency 23.3%-34.5% and ≥50% responder rate 28.5%-37.6%; in PGTC seizures, these results were 76.5% and 64.2%, respectively. Efficacy among adolescents (reduction in seizure frequency 34.8%-35.6%; ≥50% responder rate 40.9%-45.0%) and elderly people (reduction in seizure frequency 12.5%-16.9%; ≥50% responder rate 22.2%-42.9%) is similar to those in adults, and results remain comparable between Asian (reduction in seizure frequency 17.3%-38.0%) and global populations. Perampanel has been extensively studied in real-world clinical practice, with similar efficacy and safety results to the RCTs (≥50% responder rate 12.8%-75.0%; adverse events of somnolence/sedation, dizziness, ataxia, and behavioral changes). Real-world observational studies suggest that perampanel tolerability can be improved by slow titration (2mg every 2-4weeks), and bedtime administration can mitigate somnolence and dizziness. Counseling about the potential for behavioral changes and close monitoring are recommended.

Long-term treatment of RLS/WED with the selective glutamate ampa-receptor antagonist perampanel

Long-term treatment of RLS/WED with the selective glutamate ampa-receptor antagonist perampanel

Pahse 2 clinical trial with perampanel for sporadic ayotrophic lateral sclerosis

Background: Perampanel, a selective non-competitive AMPA receptor antagonist, has been reported to prevent the progression of the model mouse for sporadic amyotrophic lateral sclerosis (ALS) (AR2 mice), in which an RNA editing enzyme adenosine deaminase acting on RNA2 (ADAR2) is conditionally knocked out in the motor neurons. Because of therapeutic potency of perampanel for sporadic ALS, we planned to perform a clinical trial with perampanel for sporadic ALS.

Treatment of restless legs syndrome with the selective AMPA receptor antagonist perampanel

ObjectivesPerampanel is a selective, noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA) antagonist that has been approved for the treatment of partial seizures. Here we report on the first open study evaluating its efficacy in idiopathic restless legs syndrome (RLS). MethodsThe study was designed as a prospective two-month open trial. Twenty-two previously untreated patients diagnosed with idiopathic RLS began treatment with 2 mg perampanel, which was increased to 4 mg at week four if clinically necessary. Multiple Suggested Immobilization Tests (mSITs) followed by polysomnography were performed at baseline and at week eight. Severity ratings were performed every two weeks by means of the IRLS scale, and Clinical Global Index (CGI) subscale. The main endpoint was therapeutic response, defined as a 50% improvement in IRLS total score. ResultsTwenty patients completed the study. During the 8-week treatment period, the IRLS score improved from a mean (±standard deviation (SD)) 23.7 ± 4.2 to 11.5 ± 5.3. Twelve of 20 patients were full responders (improvement 50% in IRLS total score), and four responded partially. The mean effective dose of perampanel at the end of treatment was 3.8 mg/day. Treatment with perampanel also resulted in an improvement in the mean (±SD) periodic leg movement index from 27.8 ± 6.9 to 4.36 ± 2.0. Perampanel was well tolerated. The main side effects were dizziness, somnolence, headache, and irritability. ConclusionThese preliminary results suggest that perampanel has significant therapeutic effects on both sensory and motor symptoms. If confirmed by future controlled studies, perampanel might become a promising alternative to existing dopaminergic treatments due to its glutamatergic mechanism of action.The study provides class IV evidence supporting the therapeutic effects of perampanel in RLS/WED.

NS1209/SPD 502, A Novel Selective AMPA Antagonist for Stroke, Neuropathic Pain or Epilepsy? Drug Development Lessons Learned.

Preclinical Research The selective AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor antagonist, NS1209 (also known as SPD 502) has been explored in several research and development campaigns since its selection as a lead drug candidate in the early 1990s by the Danish biotechnology company, NeuroSearch. The compound was successively tested in animal models of stroke, neuropathic pain and epilepsy. The preclinical data to support development for the treatment of stroke were incomplete, as the compound was administered after the stroke episode, and did not protect subcortical areas of the brain. Preclinical data for neuropathic pain and epilepsy appeared more promising, but the design of the Phase IIa studies in both indications was suboptimal, and an exploratory study in neuropathic pain, like one in refractory epilepsy gave inconclusive results. Preclinical data in pain models were much less convincing than reported by the authors in abstract and discussion sections. Due to a long preclinical sequential testing phase and insufficiently powered clinical trials, NS 1209 disappeared from the CNS development pipeline, while its patent protection exclusivity was markedly reduced due to the unfortunate slow speed in development-a phenomenon far from unusual in CNS drug discovery. NeuroSearch ceased operations as an R&D entity in 2012 and its R & D portfolio was transferred to Teva Pharmaceuticals and to a spin off, Saniona A/S. Based on an in-depth case analysis of the development of NS 1209, a number of recommendations are given to reduce chances of failure during clinical development of neuropathic pain compounds and, more generally, of CNS compounds. Drug Dev Res 78 : 75-80, 2017. © 2017 Wiley Periodicals, Inc.

Ketamine treatment involves medial prefrontal cortex serotonin to induce a rapid antidepressant-like activity in BALB/cJ mice

Unlike classic serotonergic antidepressant drugs, ketamine, an NMDA receptor antagonist, exhibits a rapid and persistent antidepressant (AD) activity, at sub-anaesthetic doses in treatment-resistant depressed patients and in preclinical studies in rodents. The mechanisms mediating this activity are unclear. Here, we assessed the role of the brain serotonergic system in the AD-like activity of an acute sub-anaesthetic ketamine dose. We compared ketamine and fluoxetine responses in several behavioral tests currently used to predict anxiolytic/antidepressant-like potential in rodents. We also measured their effects on extracellular serotonin levels [5-HT]ext in the medial prefrontal cortex (mPFCx) and brainstem dorsal raphe nucleus (DRN), a serotonergic nucleus involved in emotional behavior, and on 5-HT cell firing in the DRN in highly anxious BALB/cJ mice. Ketamine (10 mg/kg i.p.) had no anxiolytic-like effect, but displayed a long lasting AD-like activity, i.e., 24 h post-administration, compared to fluoxetine (18 mg/kg i.p.). Ketamine (144%) and fluoxetine (171%) increased mPFCx [5-HT]ext compared to vehicle. Ketamine-induced AD-like effect was abolished by a tryptophan hydroxylase inhibitor, para-chlorophenylalanine (PCPA) pointing out the role of the 5-HT system in its behavioral activity. Interestingly, increase in cortical [5-HT]ext following intra-mPFCx ketamine bilateral injection (0.25 μg/side) was correlated with its AD-like activity as measured on swimming duration in the FST in the same mice. Furthermore, pre-treatment with a selective AMPA receptor antagonist (intra-DRN NBQX) blunted the effects of intra-mPFCx ketamine on both the swimming duration in the FST and mPFCx [5-HT]ext suggesting that the AD-like activity of ketamine required activation of DRN AMPA receptors and recruited the prefrontal cortex/brainstem DRN neural circuit in BALB/c mice. These results confirm a key role of cortical 5-HT release in ketamine’s AD-like activity following the blockade of glutamatergic NMDA receptors. Tight interactions between mPFCx glutamatergic and serotonergic systems may explain the differences in this activity between ketamine and fluoxetine in vivo.This article is part of the Special Issue entitled ‘Ionotropic glutamate receptors’.

Developmental Nicotine Exposure Results in Exaggerated Response to AMPA Receptor Activation in Hypoglossal Motoneurons in Neonatal Rats

Nicotine is the primary neurotoxin in tobacco products, as it has been strongly associated with altered development of neurons throughout the brain, including brainstem neurons involved in the control of breathing. Chronic nicotine exposure causes widespread desensitization of nicotinic acetylcholine receptors (nAChRs), leading to increased receptor expression, but a reduction in synaptic efficacy. Our previous work in rhythmically active hypoglossal motoneurons (XIIMNs) showed that developmental nicotine exposure (DNE) desensitizes their nAChRs and reduces excitatory synaptic input to these cells. We also showed that expression of somatic glutamate receptors was reduced, suggesting a reduction in post‐synaptic efficacy. Here we hypothesize that DNE results in increased postsynaptic responses to AMPA receptor activation in XIIMNs from neonatal rats. Whole cell voltage clamp recordings of rhythmically active XIIMNs in brainstem slices from control and DNE animals were made. AMPA (2.5 mM) was bath‐applied in the presence of TTX to isolate fast postsynaptic glutamatergic responses. Preliminary data suggest a larger AMPA‐mediated inward current and a higher charge transfer in DNE XIIMNs (DNE, n = 10; control, n = 12). All responses were blocked by CNQX (20 mM), a selective AMPA and kainate receptor antagonist, indicating that the responses were AMPAergic. These results indicate that DNE: (1) upregulates AMPA receptor expression in XIIMNs, and/or (2) changes the kinetics of AMPA receptors in order to overcome the reduced excitatory synaptic input to XIIMNs.

Inhibition of histone deacetylases enhances the function of serotoninergic neurons in organotypic raphe slice cultures

Inhibition of histone deacetylases (HDACs) is a promising approach for the treatment of mood disorders. However, the effects of HDAC inhibition on the serotonin (5-HT) system, a common target for psychiatric disorders, are poorly understood. Here, we show that a broad-spectrum HDAC inhibitor, trichostatin A (TSA), enhances the function of 5-HT neurons in organotypic raphe slice cultures. Sustained treatment with TSA (1μM) for 2 or 4 days significantly increased the 5-HT tissue content and tryptophan hydroxylase 2 (TPH2) expression, which were accompanied by hyper-acetylation of histone H3 in the promoter region of the TPH2 gene. TSA treatment for 4 days increased the extracellular 5-HT level, which was significantly suppressed in the presence of the selective AMPA receptor (AMPAR) antagonist NBQX. Moreover, the expression of both the AMPAR subunit GluA2 and Ca2+/calmodulin-dependent kinase II α (CaMKIIα) mRNAs were significantly increased by TSA treatment. Co-treatment with the CaMKII inhibitors KN-62 and KN-93 prevented the TSA-induced increase in 5-HT release, but had no effect on the increases in 5-HT tissue content. These results suggest that inhibition of HDACs increases 5-HT synthesis and release by epigenetic mechanisms, and that 5-HT release is mediated by the enhancement of AMPAR-mediated excitatory inputs and CaMKII signaling.

Perampanel Inhibition of AMPA Receptor Currents in Cultured Hippocampal Neurons

Perampanel is an aryl substituted 2-pyridone AMPA receptor antagonist that was recently approved as a treatment for epilepsy. The drug potently inhibits AMPA receptor responses but the mode of block has not been characterized. Here the action of perampanel on AMPA receptors was investigated by whole-cell voltage-clamp recording in cultured rat hippocampal neurons. Perampanel caused a slow (τ∼1 s at 3 µM), concentration-dependent inhibition of AMPA receptor currents evoked by AMPA and kainate. The rates of block and unblock of AMPA receptor currents were 1.5×105 M−1 s−1 and 0.58 s−1, respectively. Perampanel did not affect NMDA receptor currents. The extent of block of non-desensitizing kainate-evoked currents (IC50, 0.56 µM) was similar at all kainate concentrations (3–100 µM), demonstrating a noncompetitive blocking action. Parampanel did not alter the trajectory of AMPA evoked currents indicating that it does not influence AMPA receptor desensitization. Perampanel is a selective negative allosteric AMPA receptor antagonist of high-affinity and slow blocking kinetics.

PARP-1 activation causes neuronal death in the hippocampal CA1 region by increasing the expression of Ca2 +-permeable AMPA receptors

An excessive activation of poly(ADP-ribose) polymerases (PARPs) may trigger a form of neuronal death similar to that occurring in neurodegenerative disorders. To investigate this process, we exposed organotypic hippocampal slices to N-methyl-N′-nitro-N′-nitrosoguanidine (MNNG, 100μM for 5min), an alkylating agent widely used to activate PARP-1. MNNG induced a pattern of degeneration of the CA1 pyramidal cells morphologically similar to that observed after a brief period of oxygen and glucose deprivation (OGD). MNNG exposure was also associated with a dramatic increase in PARP-activity and a robust decrease in NAD+ and ATP content. These effects were prevented by PARP-1 but not PARP-2 inhibitors. In our experimental conditions, cell death was not mediated by AIF translocation (parthanatos) or caspase-dependent apoptotic processes. Furthermore, we found that PARP activation was followed by a significant deterioration of neuronal membrane properties. Using electrophysiological recordings we firstly investigated the suggested ability of ADP-ribose to open TRPM2 channels in MNNG-induced cells death, but the results we obtained showed that TRPM2 channels are not involved. We then studied the involvement of glutamate receptor-ion channel complex and we found that NBQX, a selective AMPA receptor antagonist, was able to effectively prevent CA1 neuronal loss while MK801, a NMDA antagonist, was not active. Moreover, we observed that MNNG treatment increased the ratio of GluA1/GluA2 AMPAR subunit expression, which was associated with an inward rectification of the IV relationship of AMPA sEPSCs in the CA1 but not in the CA3 subfield. Accordingly, 1-naphthyl acetyl spermine (NASPM), a selective blocker of Ca2+-permeable GluA2-lacking AMPA receptors, reduced MNNG-induced CA1 pyramidal cell death. In conclusion, our results show that activation of the nuclear enzyme PARP-1 may change the expression of membrane proteins and Ca2+ permeability of AMPA channels, thus affecting the function and survival of CA1 pyramidal cells.

The practical impact of altered dosing on perampanel plasma concentrations: Pharmacokinetic modeling from clinical studies

RationalePerampanel is a selective AMPA receptor antagonist approved for adjunctive therapy in patients with refractory partial-onset seizures. Perampanel is metabolized primarily via CYP3A4, yet it has a relatively long half-life of 105h; it is, therefore, recommended that perampanel be given once daily (preferably at bedtime). Many patients occasionally have less-than-perfect adherence to their drug regimen, and given the known pharmacokinetic interactions of perampanel with commonly used enzyme-inducing antiepileptic drugs (EIAEDs), we explored the effects of a missed dose on steady-state perampanel plasma concentrations and the ramifications of “make up” doses in these patients. Although perampanel is approved for once-daily dosing, some clinicians may elect to give perampanel as a divided dose (i.e., twice daily), so we also sought to examine the pharmacokinetic impact of twice- versus once-daily dosing. MethodsPharmacokinetic simulations were performed using validated perampanel pharmacokinetic parameters, derived from 19 phase I studies in 606 subjects, to investigate the effect on perampanel plasma concentration of (1) missing a dose of perampanel followed by delayed replacement of the missed dose, (2) missing a dose followed by resumption of scheduled therapy, and (3) missing a dose in the presence/absence of carbamazepine. Simulations were done for a typical patient receiving an 8-mg once-daily or a 4-mg twice-daily dose using the nonlinear mixed effects program, NONMEM v7.2, in conjunction with PDx-pop v5. ResultsOur results corroborate that given the pharmacokinetic characteristics of perampanel, a missed dose is unlikely to cause as much fluctuation in plasma concentration as would be expected for a drug with a short half-life. Importantly, simulations suggest that supplementing a missed dose 6–12h later, followed by continuation of the regular schedule, may not result in any significant “spikes” in perampanel plasma concentrations. Simulations demonstrated that twice-daily dosing offered little advantage in further flattening the concentration–time profile of perampanel in the adherent patient. However, fluctuations in plasma concentrations are minimized by twice-daily dosing in patients receiving concomitant EIAEDs. ConclusionsThese pharmacokinetic simulations suggest that the long half-life of perampanel may be advantageous in conferring a relatively smooth concentration–time profile with a once-daily or twice-daily dosing, even in the presence of concomitant EIAEDs. However, the results of the present study suggest that perampanel replacement is recommended for patients taking an EIAED to mitigate the potential risks associated with reduced exposure. Confirmation of the ultimate clinical impact of these findings will require further study.