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The use of Cannabis for medicinal purposes has been documented since ancient times, where one of its principal cannabinoids extracted from Cannabis sativa, cannabidiol (CBD), has emerged over the last few years as a promising molecule with anti-seizure potential. Here, we present an overview of recent literature pointing out CBD’s pharmacological profile (solubility, metabolism, drug-drug interactions, etc.,), CBD’s interactions with multiple molecular targets as well as advances in preclinical research concerning its anti-seizure effect on both acute seizure models and chronic models of epilepsy. We also highlight the recent attention that has been given to other natural cannabinoids and to synthetic derivatives of CBD as possible compounds with therapeutic anti-seizure potential. All the scientific research reviewed here encourages to continue to investigate the probable therapeutic efficacy of CBD and its related compounds not only in epilepsy but also and specially in drug-resistant epilepsy, since there is a dire need for new and effective drugs to treat this disease.

Purpose Temporal lobe epilepsy is associated with tissue abnormalities of several gray and white matter structures that are reproduced in animal models. Few longitudinal studies have focused on the identification of structural differences during epileptogenesis. The diffusion tensor model is a useful tool for evaluating cell death, gliosis, and axonal plasticity in epileptic subjects. This study aimed to evaluate temporal tissue changes after experimental status epilepticus in an animal model of chronic temporal lobe epilepsy. Methods Systemic pilocarpine-induced status epilepticus in adult Sprague-Dawley rats. Animals were scanned using diffusion tensor imaging (DTI) at three time points: prior to status epilepticus, and 24 and 64 days post-induction (early and late chronic, respectively). Fractional anisotropy, apparent diffusion coefficient, axial diffusivity (D║), and radial diffusivity (D┴) were evaluated in white (fimbria, cingulum, corpus callosum, and internal capsule) and gray (dorsal hippocampus, dentate gyrus, and CA3) matter regions for the three time points. Histological assessment of neurodegeneration in Kluver-Barrera preparations from the same animals was performed. Results Significantly reduced volume of dorsal hippocampus and fimbria of the epileptic animals was observed already at 24 days post-status epilepticus. Progressive changes of DTI parameters in both the white and gray matter structures of the experimental group were also observed. Stained sections confirmed such alterations. Conclusion Our study revealed time-dependent diffusion changes in gray and white matter structures after pilocarpine-induced status epilepticus. The characterization of these alterations over time may be potential imaging markers for epileptogenesis.

Epilepsy is a chronic brain disease that affects approximately 65 million people worldwide. However, despite the continuous development of antiepileptic drugs, over 30% patients with epilepsy progress to drug-resistant epilepsy. For this reason, it is a high priority objective in preclinical research to find novel therapeutic targets and to develop effective drugs that prevent or reverse the molecular mechanisms underlying epilepsy progression. Among these potential therapeutic targets, we highlight currently available information involving signaling pathways (Wnt/β-catenin, Mammalian Target of Rapamycin (mTOR) signaling and zinc signaling), enzymes (carbonic anhydrase), proteins (erythropoietin, copine 6 and complement system), channels (Transient Receptor Potential Vanilloid Type 1 (TRPV1) channel) and receptors (galanin and melatonin receptors). All of them have demonstrated a certain degree of efficacy not only in controlling seizures but also in displaying neuroprotective activity and in modifying the progression of epilepsy. Although some research with these specific targets has been done in relation with epilepsy, they have not been fully explored as potential therapeutic targets that could help address the unsolved issue of drug-resistant epilepsy and develop new antiseizure therapies for the treatment of epilepsy.

Introduction Spontaneous ventriculomegaly has been observed in rats that were presumed normal. Because the external phenotype of these animals is unremarkable, they can be inadvertently included in behavioral experiments, despite the considerable enlargement of the ventricular system, reduced cortical thickness, and hippocampal atrophy upon imaging. Given the role of such structures in memory consolidation, we evaluated long‐term memory retention while decision making in rats with spontaneous ventriculomegaly. Methods We studied adult male Sprague Dawley rats, identified as having spontaneous ventriculomegaly, while performing baseline magnetic resonance imaging scanning intended for a different research protocol. Control (n = 7) and experimental (n = 6) animals were submitted to a delayed‐alternation task (no delay, 30, 60, and 180 s) and an object‐in‐context recognition task. During the first task, we evaluated the number of correct choices as well as the latency to reach any of the cavities located at the end of each branch arm during each trial. The second task assessed the rodents’ ability to remember where they had previously encountered a specific object, calculating the context recognition index. Results When compared to control animals, rats with spontaneous ventriculomegaly required significantly more training sessions to reach the 80% criterion during the training phase. Moreover, they showed reduced delayed‐alternation performance in the evaluated times, reaching significance only at 180 s. Increased latencies while trying to reach the cavity were also observed. Evaluation of the long‐term memory formation during the object‐in‐context recognition task showed that subjects with ventriculomegaly spent less time investigating the familiar object, resulting in a significantly decreased recognition index value. Conclusion Our results are the first to show how spontaneous ventriculomegaly‐induced cerebral structural damage affects decision‐making behaviors, particularly when comparing between immediate and delayed trials. Moreover, this lesion disrupts the animals’ ability to recall or express contextual information., Spontaneous ventriculomegaly is a severe noninduced cerebral lesion. However, animals try to decode the challenges when exposed to memory tasks despite their grossly abnormal brain anatomy. This suggests the existence of compensation mechanisms.

The random nature of seizures poses difficult challenges for epilepsy research. There is great need for a reliable method to control the pathway to seizure onset, which would allow investigation of the mechanisms of ictogenesis and optimization of treatments. Our hypothesis is that increased random afferent synaptic activity (i.e. synaptic noise) within the epileptic focus is one endogenous method of ictogenesis. Building upon previous theoretical and in vitro work showing that synaptic noise can induce seizures, we developed a novel in vivo model of ictogenesis. By increasing the excitability of afferent connections to the hippocampus, we control the risk of temporal lobe seizures during a specific time period. The afferent synaptic activity in the hippocampus was modulated by focal microinjections of potassium chloride into the nucleus reuniens, during which the risk of seizure occurrence increased substantially. The induced seizures were qualitatively and quantitatively indistinguishable from spontaneous ones. This model thus allows direct control of the temporal lobe seizure threshold via endogenous pathways, providing a novel tool in which to investigate the mechanisms and biomarkers of ictogenesis, test for seizure threshold, and rapidly tune antiseizure treatments.

The aim of the present study was to evaluate the effects of transcranial focal electrical stimulation (TFS) on γ-aminobutyric acid (GABA) and glutamate release in the hippocampus under basal conditions and during pilocarpine-induced status epilepticus (SE). Animals were previously implanted with a guide cannula attached to a bipolar electrode into the right ventral hippocampus and a concentric ring electrode placed on the skull surface. The first microdialysis experiment was designed to determine, under basal conditions, the effects of TFS (300 Hz, 200 μs biphasic square pulses, for 30 min) on afterdischarge threshold (ADT) and the release of GABA and glutamate in the hippocampus. The results obtained indicate that at low current intensities (

As a member of the multidrug-resistance associated protein (MRP) family, MRP2 affects the brain entry of different endogenous and exogenous compounds. Considering the role of this transporter at the blood-brain barrier, the regulation is of particular interest. However, there is limited knowledge regarding the factors that regulate MRP2 in neurologic disease states. Thus, we addressed the hypothesis that MRP2 might be affected by a glutamate-induced signaling pathway that we previously identified as one key mechanism in the regulation of P-glycoprotein. Studies in isolated porcine brain capillaries confirmed that glutamate and N-methyl-d-aspartic acid (NMDA) exposure upregulates expression and function of MPR2. The involvement of the NMDA receptor was further suggested by the fact that the NMDA receptor antagonist MK-801 [(5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine], as well as the NMDA receptor glycine binding site antagonist L-701,324 [7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2(1H)-quinolinone], prevented the impact of glutamate. A role of cyclooxygenase-2 was indicated by coincubation with the cyclooxygenase-2 inhibitor celecoxib and the cyclooxygenase-1/-2 inhibitor indomethacin, which both efficaciously abolished a glutamate-induced upregulation of MRP2. Translational studies in human capillaries from surgical specimen demonstrated a relevant MRP2 efflux function and indicated an effect of glutamate exposure as well as its prevention by cyclooxygenase-2 inhibition. Taken together the findings provide first evidence for a role of a glutamate-induced NMDA receptor/cyclooxygenase-2 signaling pathway in the regulation of MRP2 expression and function. The response to excessive glutamate concentrations might contribute to overexpression of MRP2, which has been reported in neurologic diseases including epilepsy. The overexpression might have implications for brain access of various compounds including therapeutic drugs.

article i nfo Experiments were conducted to evaluate the effects of transcranial focal electrical stimulation (TFS) applied via tripolar concentric ring electrodes, alone and associated with a sub-effective dose of diazepam (DZP) on the expression of status epilepticus (SE) induced by lithium-pilocarpine (LP) and subsequent neuronal dam- age in the hippocampus. Immediately before pilocarpine injection, male Wistar rats received TFS (300 Hz, 200-μs biphasic square charge-balanced 50-mA constant current pulses for 2 min) alone or combined with a sub-effective dose of DZP (0.41 mg/kg, i.p.). In contrast with DZP or TFS alone, DZP plus TFS reduced the incidence of, and enhanced the latency to, mild and severe generalized seizures and SE induced by LP. These effects were associated with a significant reduction in the number of degenerated neurons in the hippocampus. The present study supports the notion that TFS combined with sub-effective doses of DZP may represent a therapeutic tool to induce anticonvulsant effects and reduce the SE-induced neuronal damage.

Previously we demonstrated that noninvasive transcranial focal electrical stimulation (TFS) with sub-effective doses of diazepam reduces status epilepticus (SE)-induced neuronal damage. However, it was unclear if this neuroprotective effect is a consequence of the decrease in the glutamate release. The aim of the present study was to evaluate the effects of TFS on γ-Aminobutyric acid (GABA) and glutamate release in the hippocampus during pilocarpine-induced SE. After pilocarpine administration, the rats showed progressive behavioral changes that culminated in SE with a significant increase of GABA and glutamate (95 and 128% respectively), even more evident at the end of the experiment (120 and 182% respectively), 5 hours after pilocarpine injection and was associated with the prevalence of high-voltage rhythmic spikes and increased spectral power in the 4-90 Hz bands. The TFS application during the SE decreased the convulsive expression, the prevalence of high-voltage rhythmic spikes and spectral power in 4-8 Hz and 30-90 Hz bands. These effects were associated with lower release of GABA and glutamate in the hippocampus. These results support the anticonvulsive and neuroprotective effects induced by TFS.

Breast cancer resistance protein (BCRP) functions as a major molecular gatekeeper at the blood-brain barrier. Considering its impact on access to the brain by therapeutic drugs and harmful xenobiotics, it is of particular interest to elucidate the mechanisms of its regulation. Excessive glutamate concentrations have been reported during epileptic seizures or as a consequence of different brain insults including brain ischemia. Previously, we have demonstrated that glutamate can trigger an induction of the transporter P-glycoprotein. These findings raised the question whether other efflux transporters are affected in a comparable manner. Glutamate exposure proved to down-regulate BCRP transport function and expression in isolated porcine capillaries. The reduction was efficaciously prevented by coincubation with N-methyl-d-aspartate (NMDA) receptor antagonist MK-801. The involvement of the NMDA receptor in the down-regulation of BCRP was further confirmed by experiments showing an effect of NMDA exposure on brain capillary BCRP transport function and expression. Pharmacological targeting of cyclooxygenase-1 and -2 (COX-1 and -2) using the nonselective inhibitor indomethacin, COX-1 inhibitor SC-560, and COX-2 inhibitor celecoxib revealed a contribution of COX-2 activity to the NMDA receptor's downstream signaling events affecting BCRP. Translational studies were performed using human capillaries isolated from surgical specimens of epilepsy patients. The findings confirmed a glutamate-induced down-regulation of BCRP transport activity in human capillaries, which argued against major species differences. In conclusion, our data reveal a novel mechanism of BCRP down-regulation in porcine and human brain capillaries. Moreover, together with previous data sets for P-glycoprotein, the findings point to a contrasting impact of the signaling pathway on the regulation of BCRP and P-glycoprotein. The effect of glutamate and arachidonic acid signaling on BCRP function might have implications for brain drug delivery and for radiotracer brain access in epilepsy patients and patients with other brain insults.

Unfortunately, antiepileptic drug therapy fails to control seizure activity in a relevant percentage of epilepsy patients. Epidemiological data as well as findings in human epileptic tissue and in rodent models indicate that drug resistance is a multi-factorial phenomenon with various factors contributing to therapeutic failure. Enhanced efflux transport of antiepileptic drugs as a consequence of seizure-associated up-regulation of transporters such as P-glycoprotein constitutes one factor discussed in this context. Evidence exists that expression rates of P-glycoprotein correlate with drug response in rodent models and in patients. Moreover, add-on of a Pglycoprotein modulator proved to be efficacious in a rat model of drug-resistant epilepsy. Further proof is obviously needed regarding the relative functional relevance of blood-brain barrier efflux for antiepileptic drug efficacy in epilepsy patients. Ongoing studies with positron emission tomography using transporter substrate radiotracers might provide further information. However, these studies also face major challenges considering the complexity of various factors affecting the kinetics of radiotracers in central nervous system pathologies.

Epilepsy affects approximately one percent of the world population. Antiepileptic drugs are ineffective in approximately 30% of patients and have side effects. We are developing a noninvasive, or minimally invasive, transcranial focal electrical stimulation system through our novel tripolar concentric ring electrodes to control seizures. In this study we demonstrate feasibility of an automatic seizure control system in rats with pentylenetetrazole-induced seizures through single and multiple stimulations. These stimulations are automatically triggered by a real-time electrographic seizure activity detector based on a disjunctive combination of detections from a cumulative sum algorithm and a generalized likelihood ratio test. An average seizure onset detection accuracy of 76.14% was obtained for the test set (n = 13). Detection of electrographic seizure activity was accomplished in advance of the early behavioral seizure activity in 76.92% of the cases. Automatically triggered stimulation significantly (p = 0.001) reduced the electrographic seizure activity power in the once stimulated group compared to controls in 70% of the cases. To the best of our knowledge this is the first closed-loop automatic seizure control system based on noninvasive electrical brain stimulation using tripolar concentric ring electrode electrographic seizure activity as feedback.

Hippocampal high frequency electrical stimulation (HFS) at 130 Hz has been proposed as a therapeutical strategy to control neu- rological disorders such as intractable temporal lobe epilepsy (TLE). This study was carried out to determine the effects of hippocampal HFS on the memory process and the probable involvement of amino acids. Using the autoshaping task, we found that animals receiving hippocam- pal HFS showed augmented short-term, but not long-term memory for- mation, an effect blocked by bicuculline pretreatment and associated with enhanced tissue levels of amino acids in hippocampus. In addition, microdialysis experiments revealed high extracellular levels of glutamate, aspartate, glycine, taurine, and alanine during the application of hippo- campal HFS. In contrast, GABA release augmented during HFS and remained elevated for more than 1 h after the stimulation was ended. HFS had minimal effects on glutamine release. The present results suggest that HFS has an activating effect on specific amino acids in normal hip- pocampus that may be involved in the enhanced short-term memory for- mation. These data further provide experimental support for the concept that hippocampus may be a promising target for focal stimulation to treat intractable seizures in humans. V C 2010 Wiley Periodicals, Inc.

As epilepsy affects approximately one percent of the world population, electrical stimulation of brain has recently shown potential as an additive seizure control therapy. In this study we applied focal transcranial electrical stimulation (TFS) on the surface of the skull of rats via concentric ring electrodes. We recorded electric potentials with a bipolar electrode consisting of two stainless steel wires implanted into the left ventral hippocampus. TFS current was gradually increased by 20% starting at 103 μA allowing us to assess the relationship between TFS current and both potentials recorded from the bipolar electrode and the resulting electric field. Generally, increases in TFS current resulted in increases in the electric field. This allows us to estimate what extra-cranial TFS current would be sufficient to cause the activation of neurons in the hippocampus.