Downregulation of the CB1 cannabinoid receptor and related molecular elements of the endocannabinoid system in epileptic human hippocampus

Cannabinoid receptor 2 agonist AM1241 alleviates epileptic seizures and epilepsy-associated depression via inhibiting neuroinflammation in a pilocarpine-induced chronic epilepsy mouse model

Increasing evidence suggests that cannabinoid receptor 2 (CB2R) serves as a promising anti-inflammatory target. While inflammation is known to play crucial roles in the pathogenesis of epilepsy, the involvement of CB2R in epilepsy remains unclear. This study aimed to investigate the effects of a CB2R agonist, AM1241, on epileptic seizures and depressive-like behaviors in a mouse model of chronic epilepsy induced by pilocarpine. A chronic epilepsy mouse model was established by intraperitoneal administration of pilocarpine. The endogenous cannabinoid system (eCBs) in the hippocampus was examined after status epilepticus (SE). Animals were then treated with AM1241 and compared with a vehicle-treated control group. Additionally, the role of the AMPK/NLRP3 signaling pathway was explored using the selective AMPK inhibitor dorsomorphin. Following SE, CB2R expression increased significantly in hippocampal microglia. Administration of AM1241 significantly reduced seizure frequency, immobility time in the tail suspension test, and neuronal loss in the hippocampus. In addition, AM1241 treatment attenuated microglial activation, inhibited pro-inflammatory polarization of microglia, and suppressed NLRP3 inflammasome activation in the hippocampus after SE. Further, the therapeutic effects of AM1241 were abolished by the AMPK inhibitor dorsomorphin. Our findings suggest that CB2R agonist AM1241 may alleviate epileptic seizures and its associated depression by inhibiting neuroinflammation through the AMPK/NLRP3 signaling pathway. These results provide insight into a novel therapeutic approach for epilepsy.

TRPV1 channel in the pathophysiology of epilepsy and its potential as a molecular target for the development of new antiseizure drug candidates

Identification of transient receptor potential cation channel, subfamily V member 1 (TRPV1), also known as capsaicin receptor, in 1997 was a milestone achievement in the research on temperature sensation and pain signalling. Very soon after it became evident that TRPV1 is implicated in a wide array of physiological processes in different peripheral tissues, as well as in the central nervous system, and thereby could be involved in the pathophysiology of numerous diseases. Increasing evidence suggests that modulation of TRPV1 may also affect seizure susceptibility and epilepsy. This channel is localized in brain regions associated with seizures and epilepsy, and its overexpression was found both in animal models of seizures and in brain samples from epileptic patients. Moreover, modulation of TRPV1 on non-neuronal cells (microglia, astrocytes, and/or peripheral immune cells) may have an impact on the neuroinflammatory processes that play a role in epilepsy and epileptogenesis. In this paper, we provide a comprehensive and critical overview of currently available data on TRPV1 as a possible molecular target for epilepsy management, trying to identify research gaps and future directions. Overall, several converging lines of evidence implicate TRPV1 channel as a potentially attractive target in epilepsy research but more studies are needed to exploit the possible role of TRPV1 in seizures/epilepsy and to evaluate the value of TRPV1 ligands as candidates for new antiseizure drugs.

Deletion of endocannabinoid synthesizing enzyme DAGLα from cerebellar Purkinje cells decreases social preference and elevates anxiety

The endocannabinoid (eCB) signaling system is robustly expressed in the cerebellum starting from the embryonic developmental stages to adulthood. There it plays a key role in regulating cerebellar synaptic plasticity and excitability, suggesting that impaired eCB signaling will lead to deficits in cerebellar adjustments of ongoing behaviors and cerebellar learning. Indeed, human mutations in DAGLα are associated with neurodevelopmental disorders. In this study, we show that selective deletion of the eCB synthesizing enzyme diacylglycerol lipase alpha (Daglα) from mouse cerebellar Purkinje cells (PCs) alters motor and social behaviors, disrupts short-term synaptic plasticity in both excitatory and inhibitory synapses, and reduces Purkinje cell activity during social exploration. Our results provide the first evidence for cerebellar-specific eCB regulation of social behaviors and implicate eCB regulation of synaptic plasticity and PC activity as the neural substrates contributing to these deficits.

Abstract Figure

Anandamide Attenuates Neurobehavioral Deficits and EEG Irregularities in the Chronic Sleep Deprivation Rats: The Role of Oxidative Stress and Neuroinflammation

Sleep deprivation increases stress, anxiety, and depression by altering the endocannabinoid system's function. In the present study, we aimed to investigate the anti-anxiety and anti-depressant effects of the endocannabinoid anandamide (AEA) in the chronic sleep deprivation (SD) model in rats. Adult male Wistar rats (200-250 g) were randomly divided into three groups: control + vehicle (Control), chronic sleep deprivation + vehicle (SD), and chronic sleep deprivation + 20 mg/kg AEA (SD + A). The rats were kept in a sleep deprivation device for 18 h (7 to 1 a.m.) daily for 21 days. Open-field (OFT), elevated plus maze, and forced swimming tests (FST) were used to assess anxiety and depression-like behavior. As well as the cortical EEG, CB1R mRNA expression, TNF-α, IL-6, IL-4 levels, and antioxidant activity in the brain were examined following SD induction. AEA administration significantly increased the time spent (p < 0.01), the distance traveled in the central zone (p < 0.001), and the number of climbing (p < 0.05) in the OFT; it also increased the duration and number of entries into the open arms (p < 0.01 and p < 0.05 respectively), and did not reduce immobility time in the FST (p > 0.05), AEA increased CB1R mRNA expression in the anterior and medial parts of the brain (p < 0.01), and IL-4 levels (p < 0.05). AEA also reduced IL-6 and TNF-α (p < 0.05) and modulated cortical EEG. AEA induced anxiolytic-like effects but not anti-depressant effects in the SD model in rats by modulating CB1R mRNA expression, cortical EEG, and inflammatory response.

Mapping dynamic molecular changes in hippocampal subregions after traumatic brain injury through spatial proteomics

BACKGROUND

Traumatic brain injury (TBI) often results in diverse molecular responses, challenging traditional proteomic studies that measure average changes at tissue levels and fail to capture the complexity and heterogeneity of the affected tissues. Spatial proteomics offers a solution by providing insights into sub-region-specific alterations within tissues. This study focuses on the hippocampal sub-regions, analyzing proteomic expression profiles in mice at the acute (1 day) and subacute (7 days) phases of post-TBI to understand subregion-specific vulnerabilities and long-term consequences.

METHODS

Three mice brains were collected from each group, including Sham, 1-day post-TBI and 7-day post-TBI. Hippocampal subregions were extracted using Laser Microdissection (LMD) and subsequently analyzed by label-free quantitative proteomics.

RESULTS

The spatial analysis reveals region-specific protein abundance changes, highlighting the elevation of FN1, LGALS3BP, HP, and MUG-1 in the stratum moleculare (SM), suggesting potential immune cell enrichment post-TBI. Notably, established markers of chronic traumatic encephalopathy, IGHM and B2M, exhibit specific upregulation in the dentate gyrus bottom (DG2) independent of direct mechanical injury. Metabolic pathway analysis identifies disturbances in glucose and lipid metabolism, coupled with activated cholesterol synthesis pathways enriched in SM at 7-Day post-TBI and subsequently in deeper DG1 and DG2 suggesting a role in neurogenesis and the onset of recovery. Coordinated activation of neuroglia and microtubule dynamics in DG2 suggest recovery mechanisms in less affected regions. Cluster analysis revealed spatial variations post-TBI, indicative of dysregulated neuronal plasticity and neurogenesis and further predisposition to neurological disorders. TBI-induced protein upregulation (MUG-1, PZP, GFAP, TJP, STAT-1, and CD44) across hippocampal sub-regions indicates shared molecular responses and links to neurological disorders. Spatial variations were demonstrated by proteins dysregulated in both or either of the time-points exclusively in each subregion (ELAVL2, CLIC1 in PL, CD44 and MUG-1 in SM, and SHOC2, LGALS3 in DG).

CONCLUSIONS

Utilizing advanced spatial proteomics techniques, the study unveils the dynamic molecular responses in distinct hippocampal subregions post-TBI. It uncovers region-specific vulnerabilities and dysregulated neuronal processes, and potential recovery-related pathways that contribute to our understanding of TBI's neurological consequences and provides valuable insights for biomarker discovery and therapeutic targets.

In silico analyses of the involvement of GPR55, CB1R and TRPV1: response to THC, contribution to temporal lobe epilepsy, structural modeling and updated evolution

Introduction

The endocannabinoid (eCB) system is named after the discovery that endogenous cannabinoids bind to the same receptors as the phytochemical compounds found in Cannabis. While endogenous cannabinoids include anandamide (AEA) and 2-arachidonoylglycerol (2-AG), exogenous phytocannabinoids include Δ-9 tetrahydrocannabinol (THC) and cannabidiol (CBD). These compounds finely tune neurotransmission following synapse activation, via retrograde signaling that activates cannabinoid receptor 1 (CB1R) and/or transient receptor potential cation channel subfamily V member 1 (TRPV1). Recently, the eCB system has been linked to several neurological diseases, such as neuro-ocular abnormalities, pain insensitivity, migraine, epilepsy, addiction and neurodevelopmental disorders. In the current study, we aim to: (i) highlight a potential link between the eCB system and neurological disorders, (ii) assess if THC exposure alters the expression of eCB-related genes, and (iii) identify evolutionary-conserved residues in CB1R or TRPV1 in light of their function.

Methods

To address this, we used several bioinformatic approaches, such as transcriptomic (Gene Expression Omnibus), protein-protein (STRING), phylogenic (BLASTP, MEGA) and structural (Phyre2, AutoDock, Vina, PyMol) analyzes.

Results

Using RNA sequencing datasets, we did not observe any dysregulation of eCB-related transcripts in major depressive disorders, bipolar disorder or schizophrenia in the anterior cingulate cortex, nucleus accumbens or dorsolateral striatum. Following in vivo THC exposure in adolescent mice, GPR55 was significantly upregulated in neurons from the ventral tegmental area, while other transcripts involved in the eCB system were not affected by THC exposure. Our results also suggest that THC likely induces neuroinflammation following in vitro application on mice microglia. Significant downregulation of TPRV1 occurred in the hippocampi of mice in which a model of temporal lobe epilepsy was induced, confirming previous observations. In addition, several transcriptomic dysregulations were observed in neurons of both epileptic mice and humans, which included transcripts involved in neuronal death. When scanning known interactions for transcripts involved in the eCB system (n = 12), we observed branching between the eCB system and neurophysiology, including proteins involved in the dopaminergic system. Our protein phylogenic analyzes revealed that CB1R forms a clade with CB2R, which is distinct from related paralogues such as sphingosine-1-phosphate, receptors, lysophosphatidic acid receptors and melanocortin receptors. As expected, several conserved residues were identified, which are crucial for CB1R receptor function. The anandamide-binding pocket seems to have appeared later in evolution. Similar results were observed for TRPV1, with conserved residues involved in receptor activation.

Conclusion

The current study found that GPR55 is upregulated in neurons following THC exposure, while TRPV1 is downregulated in temporal lobe epilepsy. Caution is advised when interpreting the present results, as we have employed secondary analyzes. Common ancestors for CB1R and TRPV1 diverged from jawless vertebrates during the late Ordovician, 450 million years ago. Conserved residues are identified, which mediate crucial receptor functions.

Early endocannabinoid-mediated depolarization-induced suppression of excitation delays the appearance of the epileptic phenotype in synapsin II knockout mice

The mechanism underlying the transition from the pre-symptomatic to the symptomatic state is a crucial aspect of epileptogenesis. SYN2 is a member of a multigene family of synaptic vesicle phosphoproteins playing a fundamental role in controlling neurotransmitter release. Human SYN2 gene mutations are associated with epilepsy and autism spectrum disorder. Mice knocked out for synapsin II (SynII KO) are prone to epileptic seizures that appear after 2 months of age. However, the involvement of the endocannabinoid system, known to regulate seizure development and propagation, in the modulation of the excitatory/inhibitory balance in the epileptic hippocampal network of SynII KO mice has not been explored. In this study, we investigated the impact of endocannabinoids on glutamatergic and GABAergic synapses at hippocampal dentate gyrus granule cells in young pre-symptomatic (1-2 months old) and adult symptomatic (5-8 months old) SynII KO mice. We observed an increase in endocannabinoid-mediated depolarization-induced suppression of excitation in young SynII KO mice, compared to age-matched wild-type controls. In contrast, the endocannabinoid-mediated depolarization-induced suppression of inhibition remained unchanged in SynII KO mice at both ages. This selective alteration of excitatory synaptic transmission was accompanied by changes in hippocampal endocannabinoid levels and cannabinoid receptor type 1 distribution among glutamatergic and GABAergic synaptic terminals contacting the granule cells of the dentate gyrus. Finally, inhibition of type-1 cannabinoid receptors in young pre-symptomatic SynII KO mice induced seizures during a tail suspension test. Our results suggest that endocannabinoids contribute to maintaining network stability in a genetic mouse model of human epilepsy.

Anandamide improves food intake and orexinergic neuronal activity in the chronic sleep deprivation induction model in rats by modulating the expression of the CB1 receptor in the lateral hypothalamus

Sleep deprivation alters orexinergic neuronal activity in the lateral hypothalamus (LH), which is the main regulator of sleep-wake, arousal, appetite, and energy regulation processes. Cannabinoid receptor (CBR) expression in this area is involved in modulating the function of orexin neurons. In this study, we investigated the effects of endocannabinoid anandamide (AEA) administration on improving food intake and appetite by modulating the activity of orexin neurons and CB1R expression after chronic sleep deprivation. Adult male Wistar rats (200-250 g) were randomly divided into three groups: control + vehicle (Control), chronic sleep deprivation + vehicle (SD), and chronic sleep deprivation +20 mg/kg AEA (SD + A). For SD induction, the rats were kept in a sleep deprivation device for 18 h (7 a.m. to 1 a.m.) daily for 21 days. Weight gain, food intake, the electrical power of orexin neurons, CB1R mRNA expression in hypothalamus, CB1R protein expression in the LH, TNF-α, IL-6, IL-4 levels and antioxidant activity in hypothalamus were measured after SD induction. Our results showed that AEA administration significantly improved food intake (p < 0.01), Electrical activity of orexin neurons (p < 0.05), CB1R expression in the hypothalamus (p < 0.05), and IL-4 levels (p < 0.05). AEA also reduced mRNA expression of OX1R and OX2R (p < 0.01 and p < 0.05 respectively), also IL-6 and TNF-α (p < 0.01) and MDA level (p < 0.05) in hypothalamic tissue. As a consequence, AEA modulates orexinergic system function and improves food intake by regulating the expression of the CB1 receptor in the LH in sleep deprived rats.

Cannabinoid receptor gene CNR1 is downregulated in subcortical brain samples and upregulated in blood samples of individuals with schizophrenia: A participant data systematic meta-analysis

Cannabis use leads to symptom exacerbation in schizophrenia patients, and endocannabinoid ligands have been studied as tentative schizophrenia therapeutics. Here, we aimed to characterise the connection between schizophrenia and the cannabinoid receptor 1 gene (CNR1) and explore possible mechanisms affecting its expression in schizophrenia. We performed a participant data systematic meta-analysis of CNR1 gene expression and additional endocannabinoid system genes in both brain (subcortical areas) and blood samples. We integrated eight brain sample datasets (overall 316 samples; 149 schizophrenia and 167 controls) and two blood sample datasets (overall 90 samples; 53 schizophrenia and 37 controls) while following the PRISMA meta-analysis guidelines. CNR1 was downregulated in subcortical regions and upregulated in blood samples of patients with schizophrenia. CNR2 and genes encoding endocannabinoids synthesis and degradation did not show differential expression in the brain or blood, except fatty acid amide hydrolase (FAAH), which showed a downregulation trend in blood. In addition, the brain expression levels of CNR1 and three GABA receptor genes, GABRA1, GABRA6 and GABRG2, were positively correlated (R = .57, .36, .54; p = 2.7 × 10-14 , 6.9 × 10-6 and 1.1 × 10-12 , respectively). Brain CNR1 downregulation and the positive correlation with three GABA receptor genes suggest an association with GABA neurotransmission and possible effects on negative schizophrenia symptoms. Further studies are required for clarifying the opposite CNR1 dysregulation in the brain and blood of schizophrenia patients and the potential of endocannabinoid ligands as schizophrenia therapeutics.

Control of a hippocampal recurrent excitatory circuit by cannabinoid receptor-interacting protein Gap43

The type-1 cannabinoid receptor (CB₁R) is widely expressed in excitatory and inhibitory nerve terminals, and by suppressing neurotransmitter release, its activation modulates neural circuits and brain function. While the interaction of CB₁R with various intracellular proteins is thought to alter receptor signaling, the identity and role of these proteins are poorly understood. Using a high-throughput proteomic analysis complemented with an array of in vitro and in vivo approaches in the mouse brain, we report that the C-terminal, intracellular domain of CB₁R interacts specifically with growth-associated protein of 43 kDa (GAP43). The CB₁R-GAP43 interaction occurs selectively at mossy cell axon boutons, which establish excitatory synapses with dentate granule cells in the hippocampus. This interaction impairs CB₁R-mediated suppression of mossy cell to granule cell transmission, thereby inhibiting cannabinoid-mediated anti-convulsant activity in mice. Thus, GAP43 acts as a synapse type-specific regulatory partner of CB₁R that hampers CB₁R-mediated effects on hippocampal circuit function.

Hippocampal expression of the cannabinoid receptor type 1 in canine epilepsy

Canine drug-resistant epilepsy is a prevailing issue in veterinary neurology. Alternative or additional treatment with cannabinoids is showing promising results in seizure management. A crucial component of the endocannabinoid system, cannabinoid receptor type 1 (CB1R), is heavily involved in the control of neurotransmitter release. Knowledge of its distribution in the epileptic brain would serve a better understanding of disease pathology and application of cannabinoids in dogs with epilepsy. CB1R distribution was assessed in sub-regions of hippocampus of dogs with idiopathic epilepsy, structural epilepsy and without cerebral pathology. In dogs with idiopathic epilepsy, significantly decreased CB1R expression compared to control animals was observed in CA1. In dogs with structural epilepsy, a significant increase in CB1R signal intensity in comparison to controls was observed. CB1R expression was higher in the structural group as compared to the idiopathic. Double immunofluorescence showed co-localization between CB1R and an astrocytic marker in about 50% of cells, regardless of the diagnosis. In summary, CB1R expression in canine hippocampus undergoes modification by the epileptic process and the direction of this change depends on the etiology of the disease. The distinct disease-associated CB1R expression needs to be considered in new treatment development for dogs with epilepsy.

Antitumor Potential of Antiepileptic Drugs in Human Glioblastoma: Pharmacological Targets and Clinical Benefits

Glioblastoma (GBM) is characterized by fast-growing cells, genetic and phenotypic heterogeneity, and radio-chemo-therapy resistance, contributing to its dismal prognosis. Various medical comorbidities are associated with the natural history of GBM. The most disabling and greatly affecting patients' quality of life are neurodegeneration, cognitive impairment, and GBM-related epilepsy (GRE). Hallmarks of GBM include molecular intrinsic mediators and pathways, but emerging evidence supports the key role of non-malignant cells within the tumor microenvironment in GBM aggressive behavior. In this context, hyper-excitability of neurons, mediated by glutamatergic and GABAergic imbalance, contributing to GBM growth strengthens the cancer-nervous system crosstalk. Pathogenic mechanisms, clinical features, and pharmacological management of GRE with antiepileptic drugs (AEDs) and their interactions are poorly explored, yet it is a potentially promising field of research in cancer neuroscience. The present review summarizes emerging cooperative mechanisms in oncogenesis and epileptogenesis, focusing on the neuron-to-glioma interface. The main effects and efficacy of selected AEDs used in the management of GRE are discussed in this paper, as well as their potential beneficial activity as antitumor treatment. Overall, although still many unclear processes overlapping in GBM growth and seizure onset need to be elucidated, this review focuses on the intriguing targeting of GBM-neuron mutual interactions to improve the outcome of the so challenging to treat GBM.

The study of rs324420 (C385A) polymorphism of the FAAH gene of the endocannabinoid system in patients with epilepsy and ADHD

The endocannabinoid (eCB) system regulates many physiological functions in the central nervous system. Fatty acid amide hydrolase (FAAH) is an essential enzyme in the eCB system, degrading anandamide. Single nucleotide polymorphism (SNP) rs324420 is a common genetic polymorphism of the FAAH gene and has been associated with susceptibility to neurological conditions. This study examined whether the SNP rs324420 (C385A) is associated with epilepsy and attention deficit hyperactivity disorder (ADHD). This study consists of two case-control parts. The first part comprises 250 epilepsy subjects and 250 healthy individuals as controls. The second one comprises 157 cases with ADHD and 136 healthy individuals as controls. Genotyping was carried out using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) technique. Interestingly, the FAAH C384A genotype (OR 1.755, 95 % CI 1.124-2.742, p = 0.013) and allele (OR 1.462, 95 % CI 1.006-2.124, p = 0.046) distribution showed an association with generalized epilepsy. On the other hand, this SNP was not associated with the risk of ADHD. To our knowledge, there was no study on the association between rs324420 (C385A) polymorphism and the risks of ADHD or epilepsy. This study provided the first evidence of an association between generalized epilepsy and rs324420 (C385A) of FAAH. Larger sample sizes and functional studies are warranted to explore the clinical utility of FAAH genotyping as a possible marker for increased generalized epilepsy risk.

Endocannabinoids at the synapse and beyond: implications for neuropsychiatric disease pathophysiology and treatment

Endocannabinoids (eCBs) are lipid neuromodulators that suppress neurotransmitter release, reduce postsynaptic excitability, activate astrocyte signaling, and control cellular respiration. Here, we describe canonical and emerging eCB signaling modes and aim to link adaptations in these signaling systems to pathological states. Adaptations in eCB signaling systems have been identified in a variety of biobehavioral and physiological process relevant to neuropsychiatric disease states including stress-related disorders, epilepsy, developmental disorders, obesity, and substance use disorders. These insights have enhanced our understanding of the pathophysiology of neurological and psychiatric disorders and are contributing to the ongoing development of eCB-targeting therapeutics. We suggest future studies aimed at illuminating how adaptations in canonical as well as emerging cellular and synaptic modes of eCB signaling contribute to disease pathophysiology or resilience could further advance these novel treatment approaches.

Dual effects of anandamide in the antiepileptic activity of diazepam in pentylenetetrazole-induced seizures in mice

The prototype endocannabinoid, anandamide activates both CB 1 and transient receptor potential vanilloid type 1 channels (TRPV1) receptor at different concentrations. At high concentrations, anandamide-mediated TRPV1 effects are opposite to its effects at low concentrations via CB 1 receptor. Thus, synaptic concentrations of anandamide govern the neuronal activity and consequently might affect the response of a drug. This study was undertaken to investigate the influence of high and low doses of anandamide on the anticonvulsant action of diazepam on the subcutaneous dose of pentylenetetrazole (PTZ) in Swiss mice weighing 20-25 g. Results revealed that intracerebroventricular administration of capsazepine (a TRPV1 antagonist: 1, 10, or 100 µg/mouse) and the low doses (10 µg/mouse) of anandamide, AM404 (anandamide transport inhibitor), or URB597 (fatty acid amide hydrolase inhibitor) augmented the anticonvulsant effect of diazepam. Conversely, higher dose of anandamide, AM404, URB597 (100 µg/mouse) as well as capsaicin (a TRPV1 agonist: 1, 10, or 100 µg/mouse) attenuated the protective effect of diazepam against PTZ-induced seizures. Thus, this study demonstrates that the effects of diazepam may be augmented by activating CB 1 receptors or dampened via TRPV1 receptors. The findings of the present study can be extrapolated to understand the use of TRPV1 blockers alone or in combination of benzodiazepines in the treatment of benzodiazepines-refractory status epilepticus, a condition associated with maladaptive trafficking of synaptic gamma-aminobutyric acid and glutamate receptors. However, potential clinical applications are needed to further support such preclinical studies.

The synaptic lipidome in health and disease

Adequate homeostasis of lipid, protein and carbohydrate metabolism is essential for cells to perform highly specific tasks in our organism, and the brain, with its uniquely high energetic requirements, posesses singular characteristics. Some of these are related to its extraordinary dotation of synapses, the specialized subcelluar structures where signal transmission between neurons occurs in the central nervous system. The post-synaptic compartment of excitatory synapses, the dendritic spine, harbors key molecules involved in neurotransmission tightly packed within a minute volume of a few femtoliters. The spine is further compartmentalized into nanodomains that facilitate the execution of temporo-spatially separate functions in the synapse. Lipids play important roles in this structural and functional compartmentalization and in mechanisms that impact on synaptic transmission. This review analyzes the structural and dynamic processes involving lipids at the synapse, highlighting the importance of their homeostatic balance for the physiology of this complex and highly specialized structure, and underscoring the pathologies associated with disbalances of lipid metabolism, particularly in the perinatal and late adulthood periods of life. Although small variations of the lipid profile in the brain take place throughout the adult lifespan, the pathophysiological consequences are clinically manifested mostly during late adulthood. Disturbances in lipid homeostasis in the perinatal period leads to alterations during nervous system development, while in late adulthood they favor the occurrence of neurodegenerative diseases.

Hyperthermia-Induced Seizures Enhance Brain Concentrations of the Endocannabinoid-Related Linoleoyl Glycerols in a Scn1a+/- Mouse Model of Dravet Syndrome

Introduction: The endocannabinoid system contributes to the homeostatic response to seizure activity in epilepsy, a disease of brain hyperexcitability. Indeed, studies using conventional epilepsy models have shown that seizures increase endocannabinoids in the brain. However, it is unknown whether endocannabinoids and structurally related fatty acid amides and monoacylglycerols are similarly released in response to acute seizures in animal models of drug-resistant epilepsy. Therefore, in this study, we investigated whether a hyperthermia-induced seizure increased concentrations of endocannabinoids and related signaling lipids in the Scn1a^+/- mouse model of Dravet syndrome. Materials and Methods: We compared hippocampal concentrations of the major endocannabinoids and related monoglycerols and N-acylethanolamines in wild-type mice, naïve Scn1a^+/- mice, and Scn1a^+/- mice primed with a single, hyperthermia-induced, generalized tonic-clonic seizure. Samples were collected 5 and 60 min following the seizure and then analyzed with LC-MS/MS. Results: We found that a hyperthermia-induced seizure in Scn1a^+/- mice did not affect hippocampal concentrations of the major endocannabinoids, 2-AG and anandamide, or the N-acylethanolamines studied, although the sampling of tissue 5 min postseizure may have been too late to capture any effect on these lipids. Heterozygous deletion of Scn1a alone did not affect these lipid signaling molecules. Notably, however, we found that a hyperthermia-induced seizure significantly increased hippocampal concentrations of the monoacylglycerols, 2-linoleoyl glycerol (2-LG) and 1-linoleoyl glycerol (1-LG), in Scn1a^+/- mice. Conclusions: Our results show the unprecedented elevation of the lesser-studied endocannabinoid-related monoacylglycerols, 2-LG and 1-LG, following a hyperthermia-induced seizure in a mouse model of Dravet syndrome. Future research is needed to comprehensively explore the function of these lipid signaling molecules during seizure activity and whether their actions can be exploited to develop new therapeutics.

Cannabinoid receptor 1-labeled boutons in the sclerotic dentate gyrus of epileptic sea lions

Pathology in the dentate gyrus, including sclerosis, is a hallmark of temporal lobe epilepsy, and reduced inhibition to dentate granule cells may contribute to epileptogenesis. The perisomatic-targeting axonal boutons of parvalbumin-expressing interneurons decrease in proportion with granule cells in temporal lobe epilepsy. In contrast, dendrite-targeting axonal boutons of somatostatin-expressing interneurons sprout exuberantly in temporal lobe epilepsy. A third major class of GABAergic interneurons expresses cannabinoid receptor type 1 (CB1) on their terminal boutons, but there is conflicting evidence as to whether these boutons are increased or decreased in temporal lobe epilepsy. Naturally occurring temporal lobe epilepsy in California sea lions, with unilateral or bilateral sclerosis, offers the benefit of neuroanatomy and neuropathology akin to humans, but with the advantage that the entirety of both hippocampi from control and epileptic brains can be studied. Stereological quantification in the dentate gyrus revealed that sclerotic hippocampi from epileptic sea lions had fewer CB1-labeled boutons than controls. However, the reduction in the number of granule cells was greater, resulting in increased CB1-labeled boutons per granule cell in sclerotic hippocampi at temporal levels. This suggests that although CB1-expressing boutons are decreased in sclerotic dentate gyri, surviving cells have enhanced innervation from these boutons in epileptic sea lions.

The GABAergic System and Endocannabinoids in Epilepsy and Seizures: What Can We Expect from Plant Oils?

Seizures and epilepsy are some of the most common serious neurological disorders, with approximately 80% of patients living in developing/underdeveloped countries. However, about one in three patients do not respond to currently available pharmacological treatments, indicating the need for research into new anticonvulsant drugs (ACDs). The GABAergic system is the main inhibitory system of the brain and has a central role in seizures and the screening of new ACD candidates. It has been demonstrated that the action of agents on endocannabinoid receptors modulates the balance between excitatory and inhibitory neurotransmitters; however, studies on the anticonvulsant properties of endocannabinoids from plant oils are relatively scarce. The Amazon region is an important source of plant oils that can be used for the synthesis of new fatty acid amides, which are compounds analogous to endocannabinoids. The synthesis of such compounds represents an important approach for the development of new anticonvulsant therapies.

Neuroplastic alterations in cannabinoid receptors type 1 (CB1) in animal models of epileptic seizures

Currently, there is an urgent need to better comprehend neuroplastic alterations in cannabinoid receptors type 1 (CB1) and to understand the biological meaning of these alterations in epileptic disorders. The present study reviewed neuroplastic changes in CB1 distribution, expression, and functionality in animal models of epileptic seizures. Neuroplastic alterations in CB1 were consistently observed in chemical, genetic, electrical, and febrile seizure models. Most studies assessed changes in hippocampal and cortical CB1, while thalamic, hypothalamic, and brainstem nuclei were rarely investigated. Additionally, the relationship between CB1 alteration and the control of brain excitability through modulation of specific neuronal networks, such as striatonigral, nigrotectal and thalamocortical pathways, and inhibitory projections to hippocampal pyramidal neurons, were all presented and discussed in the present review. Neuroplastic alterations in CB1 detected in animal models of epilepsy may reflect two different scenarios: (1) endogenous adaptations aimed to control neuronal hyperexcitability in epilepsy or (2) pathological alterations that facilitate neuronal hyperexcitability. Additionally, a better comprehension of neuroplastic and functional alterations in CB1 can improve pharmacological therapies for epilepsies and their comorbidities.

Reorganization of Parvalbumin Immunopositive Perisomatic Innervation of Principal Cells in Focal Cortical Dysplasia Type IIB in Human Epileptic Patients

Focal cortical dysplasia (FCD) is one of the most common causes of drug-resistant epilepsy. As several studies have revealed, the abnormal functioning of the perisomatic inhibitory system may play a role in the onset of seizures. Therefore, we wanted to investigate whether changes of perisomatic inhibitory inputs are present in FCD. Thus, the input properties of abnormal giant- and control-like principal cells were examined in FCD type IIB patients. Surgical samples were compared to controls from the same cortical regions with short postmortem intervals. For the study, six subjects were selected/each group. The perisomatic inhibitory terminals were quantified in parvalbumin and neuronal nuclei double immunostained sections using a confocal fluorescent microscope. The perisomatic input of giant neurons was extremely abundant, whereas control-like cells of the same samples had sparse inputs. A comparison of pooled data shows that the number of parvalbumin-immunopositive perisomatic terminals contacting principal cells was significantly larger in epileptic cases. The analysis showed some heterogeneity among epileptic samples. However, five out of six cases had significantly increased perisomatic input. Parameters of the control cells were homogenous. The reorganization of the perisomatic inhibitory system may increase the probability of seizure activity and might be a general mechanism of abnormal network activity.

The endocannabinoid system impacts seizures in a mouse model of Dravet syndrome

Dravet syndrome is a catastrophic childhood epilepsy with multiple seizure types that are refractory to treatment. The endocannabinoid system regulates neuronal excitability so a deficit in endocannabinoid signaling could lead to hyperexcitability and seizures. Thus, we sought to determine whether a deficiency in the endocannabinoid system might contribute to seizure phenotypes in a mouse model of Dravet syndrome and whether enhancing endocannabinoid tone is anticonvulsant. Scn1a^+/- mice model the clinical features of Dravet syndrome: hyperthermia-induced seizures, spontaneous seizures and reduced survival. We examined whether Scn1a^+/- mice exhibit deficits in the endocannabinoid system by measuring brain cannabinoid receptor expression and endocannabinoid concentrations. Next, we determined whether pharmacologically enhanced endocannabinoid tone was anticonvulsant in Scn1a^+/- mice. We used GAT229, a positive allosteric modulator of the cannabinoid (CB₁) receptor, and ABX-1431, a compound that inhibits the degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG). The Scn1a^+/- phenotype is strain-dependent with mice on a 129S6/SvEvTac (129) genetic background having no overt phenotype and those on an F1 (129S6/SvEvTac x C57BL/6J) background exhibiting a severe epilepsy phenotype. We observed lower brain cannabinoid CB₁ receptor expression in the seizure-susceptible F1 compared to seizure-resistant 129 strain, suggesting an endocannabinoid deficiency might contribute to seizure susceptibility. GAT229 and ABX-1431 were anticonvulsant against hyperthermia-induced seizures. However, subchronic ABX1431 treatment increased spontaneous seizure frequency despite reducing seizure severity. Cnr1 is a putative genetic modifier of epilepsy in the Scn1a^+/- mouse model of Dravet syndrome. Compounds that increase endocannabinoid tone could be developed as novel treatments for Dravet syndrome.

Endocannabinoid-Mediated Control of Neural Circuit Excitability and Epileptic Seizures

Research on endocannabinoid signaling has greatly advanced our understanding of how the excitability of neural circuits is controlled in health and disease. In general, endocannabinoid signaling at excitatory synapses suppresses excitability by inhibiting glutamate release, while that at inhibitory synapses promotes excitability by inhibiting GABA release, although there are some exceptions in genetically epileptic animal models. In the epileptic brain, the physiological distributions of endocannabinoid signaling molecules are disrupted during epileptogenesis, contributing to the occurrence of spontaneous seizures. However, it is still unknown how endocannabinoid signaling changes during seizures and how the redistribution of endocannabinoid signaling molecules proceeds during epileptogenesis. Recent development of cannabinoid sensors has enabled us to investigate endocannabinoid signaling in much greater spatial and temporal details than before. Application of cannabinoid sensors to epilepsy research has elucidated activity-dependent changes in endocannabinoid signaling during seizures. Furthermore, recent endocannabinoid research has paved the way for the clinical use of cannabidiol for the treatment of refractory epilepsy, such as Dravet syndrome, Lennox-Gastaut syndrome and tuberous sclerosis complex. Cannabidiol significantly reduces seizures and is considered to have comparable tolerability to conventional antiepileptic drugs. In this article, we introduce recent advances in research on the roles of endocannabinoid signaling in epileptic seizures and discuss future directions.

Commonalities for comorbidity: Overlapping features of the endocannabinoid system in depression and epilepsy

A wealth of clinical and pre-clinical data supports a bidirectional comorbidity between depression and epilepsy. This suggests commonalities in underlying mechanisms that may serve as targets for more effective treatment strategies. Unfortunately, many patients with this comorbidity are highly refractory to current treatment strategies, while others experience a worsening of one arm of the comorbidity when treating the other arm. This highlights the need for novel pharmaceutical targets that may provide safe and effective relief for both depression and epilepsy symptoms. The endocannabinoid system (ECS) of the brain has become an area of intense interest for possible roles in depression and epilepsy. Several existing literature reviews have provided in-depth analysis of the involvement of various aspects of the ECS in depression or epilepsy separately, while others have addressed the effectiveness of different treatment strategies targeting the ECS in either condition individually. However, there is not currently a review that considers the ECS when both conditions are comorbid. This mini-review will address areas of common overlap between the ECS in depression and in epilepsy, such as commonalities in endocannabinoids themselves, their receptors, and degradative enzymes. These areas of overlap will be discussed alongside their implications for treatment of this challenging comorbidity.

Perisomatic Inhibition and Its Relation to Epilepsy and to Synchrony Generation in the Human Neocortex

Inhibitory neurons innervating the perisomatic region of cortical excitatory principal cells are known to control the emergence of several physiological and pathological synchronous events, including epileptic interictal spikes. In humans, little is known about their role in synchrony generation, although their changes in epilepsy have been thoroughly investigated. This paper demonstraits how parvalbumin (PV)- and type 1 cannabinoid receptor (CB1R)-positive perisomatic interneurons innervate pyramidal cell bodies, and their role in synchronous population events spontaneously emerging in the human epileptic and non-epileptic neocortex, in vitro. Quantitative electron microscopy showed that the overall, PV+ and CB1R+ somatic inhibitory inputs remained unchanged in focal cortical epilepsy. On the contrary, the size of PV-stained synapses increased, and their number decreased in epileptic samples, in synchrony generating regions. Pharmacology demonstrated—in conjunction with the electron microscopy—that although both perisomatic cell types participate, PV+ cells have stronger influence on the generation of population activity in epileptic samples. The somatic inhibitory input of neocortical pyramidal cells remained almost intact in epilepsy, but the larger and consequently more efficient somatic synapses might account for a higher synchrony in this neuron population. This, together with epileptic hyperexcitability, might make a cortical region predisposed to generate or participate in hypersynchronous events.

Targeting Endocannabinoid System in Epilepsy: For Good or for Bad

Epilepsy is a neurological disorder with a high prevalence worldwide. Several studies carried out during the last decades indicate that the administration of cannabinoids as well as the activation of the endocannabinoid system (ECS) represent a therapeutic strategy to control epilepsy. However, there are controversial studies indicating that activation of ECS results in cell damage, inflammation and neurotoxicity, conditions that facilitate the seizure activity. The present review is focused to present findings supporting this issue. According to the current discrepancies, it is relevant to elucidate the different effects induced by the activation of ECS and determine the conditions under which it facilitates the seizure activity.

The Endocannabinoid System in Glial Cells and Their Profitable Interactions to Treat Epilepsy: Evidence from Animal Models

Epilepsy is one of the most common neurological conditions. Yearly, five million people are diagnosed with epileptic-related disorders. The neuroprotective and therapeutic effect of (endo)cannabinoid compounds has been extensively investigated in several models of epilepsy. Therefore, the study of specific cell-type-dependent mechanisms underlying cannabinoid effects is crucial to understanding epileptic disorders. It is estimated that about 100 billion neurons and a roughly equal number of glial cells co-exist in the human brain. The glial population is in charge of neuronal viability, and therefore, their participation in brain pathophysiology is crucial. Furthermore, glial malfunctioning occurs in a wide range of neurological disorders. However, little is known about the impact of the endocannabinoid system (ECS) regulation over glial cells, even less in pathological conditions such as epilepsy. In this review, we aim to compile the existing knowledge on the role of the ECS in different cell types, with a particular emphasis on glial cells and their impact on epilepsy. Thus, we propose that glial cells could be a novel target for cannabinoid agents for treating the etiology of epilepsy and managing seizure-like disorders.

Toward Understanding the Diverse Roles of Perisomatic Interneurons in Epilepsy

Epileptic seizures are associated with excessive neuronal spiking. Perisomatic γ-aminobutyric acid (GABA)ergic interneurons specifically innervate the subcellular domains of postsynaptic excitatory cells that are critical for spike generation. With a revolution in transcriptomics-based cell taxonomy driving the development of novel transgenic mouse lines, selectively monitoring and modulating previously elusive interneuron types is becoming increasingly feasible. Emerging evidence suggests that the three types of hippocampal perisomatic interneurons, axo-axonic cells, along with parvalbumin- and cholecystokinin-expressing basket cells, each follow unique activity patterns in vivo, suggesting distinctive roles in regulating epileptic networks.

Δ9-Tetrahydrocannabinol inhibits Hedgehog-dependent patterning during development

Many developmental disorders are thought to arise from an interaction between genetic and environmental risk factors. The Hedgehog (HH) signaling pathway regulates myriad developmental processes, and pathway inhibition is associated with birth defects, including holoprosencephaly (HPE). Cannabinoids are HH pathway inhibitors, but little is known of their effects on HH-dependent processes in mammalian embryos, and their mechanism of action is unclear. We report that the psychoactive cannabinoid Δ9-tetrahydrocannabinol (THC) induces two hallmark HH loss-of-function phenotypes (HPE and ventral neural tube patterning defects) in Cdon mutant mice, which have a subthreshold deficit in HH signaling. THC therefore acts as a 'conditional teratogen', dependent on a complementary but insufficient genetic insult. In vitro findings indicate that THC is a direct inhibitor of the essential HH signal transducer smoothened. The canonical THC receptor, cannabinoid receptor-type 1, is not required for THC to inhibit HH signaling. Cannabis consumption during pregnancy may contribute to a combination of risk factors underlying specific developmental disorders. These findings therefore have significant public health relevance.

Endocannabinoids Released in the Ventral Tegmental Area During Copulation to Satiety Modulate Changes in Glutamate Receptors Associated With Synaptic Plasticity Processes

Endocannabinoids modulate mesolimbic (MSL) dopamine (DA) neurons firing at the ventral tegmental area (VTA). These neurons are activated by copulation, increasing DA release in nucleus accumbens (NAcc). Copulation to satiety in male rats implies repeated ejaculation within a short period (around 2.5 h), during which NAcc dopamine concentrations remain elevated, suggesting continuous neuronal activation. During the 72 h that follow copulation to satiety, males exhibit long-lasting changes suggestive of brain plasticity processes. Enhanced DA neuron activity triggers the synthesis and release of endocannabinoids (eCBs) in the VTA, which participate in several long-term synaptic plasticity processes. Blockade of cannabinoid type 1 receptors (CB1Rs) during copulation to satiety interferes with the appearance of the plastic changes. Glutamatergic inputs to the VTA express CB1Rs and contribute to DA neuron burst firing and synaptic plasticity. We hypothesized that eCBs, released during copulation to satiety, would activate VTA CB1Rs and modulate synaptic plasticity processes involving glutamatergic transmission. To test this hypothesis, we determined changes in VTA CB1R density, phosphorylation, and internalization in rats that copulated to satiety 24 h earlier as compared both to animals that ejaculated only once and to sexually experienced unmated males. Changes in glutamate AMPAR and NMDAR densities and subunit composition and in ERK1/2 activation were determined in the VTA of males that copulated to satiety in the presence or absence of AM251, a CB1R antagonist. The CB1R density decreased and the proportion of phosphorylated CB1Rs increased in the animals that copulated compared to control rats. The CB1R internalization was detected only in sexually satiated males. A decrease in α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor (AMPAR) density, blocked by AM251 pretreatment, and an increase in the proportion of GluA2-AMPARs occurred in sexually satiated rats. GluN2A- N-methyl-D-aspartate receptor (NMDAR) expression decreased, and GluN2B-NMDARs increased in these animals, both of which were prevented by AM251 pre-treatment. An increase in phosphorylated ERK1/2 emerged in males copulating to satiety in the presence of AM251. Results demonstrate that during copulation to satiety, eCBs activate CB1Rs in the VTA, producing changes in glutamate receptors compatible with a reduced neuronal activation. These changes could play a role in the induction of the long-lasting physiological changes that characterize sexually satiated rats.

Therapeutic potential of cannabidivarin for epilepsy and autism spectrum disorder

Recent years have seen a renewed interest on the possible therapeutic exploitations of specific cannabinoids derived from the Cannabis sativa plant. Thus far, the most studied non-psychotomimetic cannabinoid is cannabidiol (CBD), which has shown promising therapeutic potential for relieving a variety of neurological diseases. However, also its propyl analogue, cannabidivarin (CBDV), has recently gained much attention as a potential therapeutic agent for the management of disabling neurological conditions. This review aims at providing a comprehensive and updated overview of the available animal and human data, which have investigated the possible therapeutic potential of CBDV for the management of epilepsy and autism spectrum disorder.

Functional Connectivity Derived From Electroencephalogram in Pharmacoresistant Epileptic Encephalopathy Using Cannabidiol as Adjunctive Antiepileptic Therapy

To explore brain function using functional connectivity and network topology derived from electroencephalogram (EEG) in patients with pharmacoresistant epileptic encephalopathy with cannabidiol as adjunctive antiepileptic treatment. Sixteen epileptic patients participated in the study, six of whom had epileptic encephalopathy with a stable dose of cannabidiol Epidiolex (CBD) as adjunctive therapy. Functional connectivity derived from EEG was analyzed based on the synchronization likelihood (SL). The analysis also included reconstructing graph-theoretic measures from the synchronization matrix. Comparison of functional connectivity data between each pathological group with the control group was carried out using a nonparametric permutation test applied to SL values between pairs of electrodes for each frequency band. To compare the association patterns between graph-theoretical properties of each pathological group with the control group, Z Crawford was calculated as a measure of distance. There were differences between pairs of electrodes in all frequency bands evaluated in encephalopathy epileptic patients with CBD adjunctive therapy compared with the control (p < 0.05, permutation test). In the epileptic encephalopathy group without CBD therapy, the SL values were higher than in the control group for the beta, theta, and delta EEG frequency bands, and lower for the alpha frequency band. Interestingly, patients who had CBD as adjunctive therapy demonstrated greater synchronization for all frequency bands, showing less spatial distribution for alpha frequency compared with the control. When comparing both epileptic groups, those patients who had adjunctive CBD treatment also showed increased synchronization for all frequency bands. In epileptic encephalopathy with adjunctive CBD therapy, the pattern of differences for graph-theoretical measures according to Z Crawford indicated less segregation and greater integration suggesting a trend towards the random organization of the network principally for alpha and beta EEG bands. This exploratory study revealed a tendency to an overconnectivity with a random network topology mainly for fast EEG bands in epileptic encephalopathy patients using CBD adjunctive therapy. It can therefore be assumed that the CBD treatment could be related to inhibition of the transition of the interictal to ictal state and/or to the improvement of EEG organization and brain function.

Endocannabinoid-serotonin systems interaction in health and disease

Endocannabinoid (eCB) and serotonin (5-HT) neuromodulatory systems work both independently and together to finely orchestrate neuronal activity throughout the brain to strongly sculpt behavioral functions. Surprising parallelism between the behavioral effects of 5-HT and eCB activity has been widely reported, including the regulation of emotional states, stress homeostasis, cognitive functions, food intake and sleep. The distribution pattern of the 5-HT system and the eCB molecular elements in the brain display a strong overlap and several studies report a functional interplay and even a tight interdependence between eCB/5-HT signaling. In this review, we examine the available evidence of the interaction between the eCB and 5-HT systems. We first introduce the eCB system, then we describe the eCB/5-HT crosstalk at the neuronal and synaptic levels. Finally, we explore the potential eCB/5-HT interaction at the behavioral level with the implication for psychiatric and neurological disorders. The precise elucidation of how this neuromodulatory interaction dynamically regulates biological functions may lead to the development of more targeted therapeutic strategies for the treatment of depressive and anxiety disorders, psychosis and epilepsy.

Cannabinoid Receptor Interacting Protein 1a (CRIP1a) in Health and Disease

Endocannabinoid signaling depends upon the CB₁ and CB₂ cannabinoid receptors, their endogenous ligands anandamide and 2-arachidonoylglycerol, and intracellular proteins that mediate responses via the C-terminal and other intracellular receptor domains. The CB₁ receptor regulates and is regulated by associated G proteins predominantly of the Gi/o subtypes, β-arrestins 1 and 2, and the cannabinoid receptor-interacting protein 1a (CRIP1a). Evidence for a physiological role for CRIP1a is emerging as data regarding the cellular localization and function of CRIP1a are generated. Here we summarize the neuronal distribution and role of CRIP1a in endocannabinoid signaling, as well as discuss investigations linking CRIP1a to development, vision and hearing sensory systems, hippocampus and seizure regulation, and psychiatric disorders including schizophrenia. We also examine the genetic and epigenetic association of CRIP1a within a variety of cancer subtypes. This review provides evidence upon which to base future investigations on the function of CRIP1a in health and disease.

Insights into Potential Targets for Therapeutic Intervention in Epilepsy

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.

Cannabidiol in epilepsy: The indications and beyond

Epilepsy, although common, remains difficult to treat with as much as 30% of patients having treatment-resistant conditions. Lennox-Gastaut syndrome and Dravet syndrome are childhood-onset epilepsies and among the most difficult to treat. Cannabidiol has been approved by the Food and Drug Administration to treat these conditions in individuals over 2 years of age; however, there is a great deal of interest in off-label use. This article examines 3 cases: 1 of a patient with Lennox-Gastaut syndrome, 1 of off-label use of cannabidiol to treat epilepsy, and 1 of nonprescription forms of cannabidiol to treat epilepsy.

Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases

The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.

Neural Stem Cells and Cannabinoids in the Spotlight as Potential Therapy for Epilepsy

Epilepsy is one of the most common brain diseases worldwide, having a huge burden in society. The main hallmark of epilepsy is the occurrence of spontaneous recurrent seizures, having a tremendous impact on the lives of the patients and of their relatives. Currently, the therapeutic strategies are mostly based on the use of antiepileptic drugs, and because several types of epilepsies are of unknown origin, a high percentage of patients are resistant to the available pharmacotherapy, continuing to experience seizures overtime. Therefore, the search for new drugs and therapeutic targets is highly important. One key aspect to be targeted is the aberrant adult hippocampal neurogenesis (AHN) derived from Neural Stem Cells (NSCs). Indeed, targeting seizure-induced AHN may reduce recurrent seizures and shed some light on the mechanisms of disease. The endocannabinoid system is a known modulator of AHN, and due to the known endogenous antiepileptic properties, it is an interesting candidate for the generation of new antiepileptic drugs. However, further studies and clinical trials are required to investigate the putative mechanisms by which cannabinoids can be used to treat epilepsy. In this manuscript, we will review how cannabinoid-induced modulation of NSCs may promote neural plasticity and whether these drugs can be used as putative antiepileptic treatment.

Low brain endocannabinoids associated with persistent non-goal directed nighttime hyperactivity after traumatic brain injury in mice

Traumatic brain injury (TBI) is a frequent cause of chronic headache, fatigue, insomnia, hyperactivity, memory deficits, irritability and posttraumatic stress disorder. Recent evidence suggests beneficial effects of pro-cannabinoid treatments. We assessed in mice levels of endocannabinoids in association with the occurrence and persistence of comparable sequelae after controlled cortical impact in mice using a set of long-term behavioral observations in IntelliCages, motor and nociception tests in two sequential cohorts of TBI/sham mice. TBI mice maintained lower body weights, and they had persistent low levels of brain ethanolamide endocannabinoids (eCBs: AEA, OEA, PEA) in perilesional and subcortical ipsilateral brain tissue (6 months), but rapidly recovered motor functions (within days), and average nociceptive responses were within normal limits, albeit with high variability, ranging from loss of thermal sensation to hypersensitivity. TBI mice showed persistent non-goal directed nighttime hyperactivity, i.e. they visited rewarding and non-rewarding operant corners with high frequency and random success. On successful visits, they made more licks than sham mice resulting in net over-licking. The lower the eCBs the stronger was the hyperactivity. In reward-based learning and reversal learning tasks, TBI mice were not inferior to sham mice, but avoidance memory was less stable. Hence, the major late behavioral TBI phenotype was non-goal directed nighttime hyperactivity and "over-licking" in association with low ipsilateral brain eCBs. The behavioral phenotype would agree with a "post-TBI hyperactivity disorder". The association with persistently low eCBs in perilesional and subcortical regions suggests that eCB deficiency contribute to the post-TBI psychopathology.

Receptors and Channels Possibly Mediating the Effects of Phytocannabinoids on Seizures and Epilepsy

Epilepsy contributes to approximately 1% of the global disease burden. By affecting especially young children as well as older persons of all social and racial variety, epilepsy is a present disorder worldwide. Currently, only 65% of epileptic patients can be successfully treated with antiepileptic drugs. For this reason, alternative medicine receives more attention. Cannabis has been cultivated for over 6000 years to treat pain and insomnia and used since the 19th century to suppress epileptic seizures. The two best described phytocannabinoids, (−)-trans-Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD) are claimed to have positive effects on different neurological as well as neurodegenerative diseases, including epilepsy. There are different cannabinoids which act through different types of receptors and channels, including the cannabinoid receptor 1 and 2 (CB₁, CB₂), G protein-coupled receptor 55 (GPR55) and 18 (GPR18), opioid receptor µ and δ, transient receptor potential vanilloid type 1 (TRPV1) and 2 (TRPV2), type A γ-aminobutyric acid receptor (GABA_AR) and voltage-gated sodium channels (VGSC). The mechanisms and importance of the interaction between phytocannabinoids and their different sites of action regarding epileptic seizures and their clinical value are described in this review.

Possible therapeutic applications of cannabis in the neuropsychopharmacology field

Cannabis use induces a plethora of actions on the CNS via its active chemical ingredients, the so-called phytocannabinoids. These compounds have been frequently associated with the intoxicating properties of cannabis preparations. However, not all phytocannabinoids are psychotropic, and, irrespective of whether they are psychotropic or not, they have also shown numerous therapeutic properties. These properties are mostly associated with their ability to modulate the activity of an intercellular communication system, the so-called endocannabinoid system, which is highly active in the CNS and has been found altered in many neurological disorders. Specifically, this includes the neuropsychopharmacology field, with diseases such as schizophrenia and related psychoses, anxiety-related disorders, mood disorders, addiction, sleep disorders, post-traumatic stress disorder, anorexia nervosa and other feeding-related disorders, dementia, epileptic syndromes, as well as autism, fragile X syndrome and other neurodevelopment-related disorders. Here, we gather, from a pharmacological and biochemical standpoint, the recent advances in the study of the therapeutic relevance of the endocannabinoid system in the CNS, with especial emphasis on the neuropsychopharmacology field. We also illustrate the efforts that are currently being made to investigate at the clinical level the potential therapeutic benefits derived from elevating or inhibiting endocannabinoid signaling in animal models of neuropsychiatric disorders.

Anandamide Signaling Augmentation Rescues Amygdala Synaptic Function and Comorbid Emotional Alterations in a Model of Epilepsy

Epilepsy is often associated with emotional disturbances and the endocannabinoid (eCB) system tunes synaptic transmission in brain regions regulating emotional behavior. Thus, persistent alteration of eCB signaling after repeated seizures may contribute to the development of epilepsy-related emotional disorders. Here we report that repeatedly eliciting seizures (kindling) in the amygdala caused a long-term increase in anxiety and impaired fear memory retention, which was paralleled by an imbalance in GABA/glutamate presynaptic activity and alteration of synaptic plasticity in the basolateral amygdala (BLA), in male rats. Anandamide (AEA) content was downregulated after repeated seizures, and pharmacological enhancement of AEA signaling rescued seizure-induced anxiety by restoring the tonic control of the eCB signaling over glutamatergic transmission. Moreover, AEA signaling augmentation also rescued the seizure-induced alterations of fear memory by restoring the phasic control of eCB signaling over GABAergic activity and plasticity in the BLA. These results indicate that modulation of AEA signaling represents a potential and promising target for the treatment of comorbid emotional dysfunction associated with epilepsy.SIGNIFICANCE STATEMENT Epilepsy is a heterogeneous neurologic disorder commonly associated with comorbid emotional alterations. However, the management of epilepsy is usually restricted to the control of seizures. The endocannabinoid (eCB) system, particularly anandamide (AEA) signaling, controls neuronal excitability and seizure expression and regulates emotional behavior. We found that repeated seizures cause an allostatic maladaptation of AEA signaling in the amygdala that drives emotional alterations. Boosting AEA signaling through inhibition of its degradative enzyme, fatty acid amide hydrolase (FAAH), restored both synaptic and behavioral alterations. FAAH inhibitors dampen seizure activity in animal models and are used in clinical studies to treat the negative consequences associated with stress. Thereby, they are accessible and can be clinically evaluated to treat both seizures and comorbid conditions associated with epilepsy.

Anandamide Metabolites Protect against Seizures through the TRP Channel Water Witch in Drosophila melanogaster

Endocannabinoids protect against seizures, but their mechanism of action is still unclear, as they can have effects independent of known cannabinoid receptors. Using Drosophila melanogaster, which lacks canonical cannabinoid receptors, we report that the endocannabinoids anandamide and 2-arachidonoylglycerol protect against seizures in multiple fly seizure models. Surprisingly, inhibition of anandamide catabolism renders flies insensitive to protection by anandamide, indicating that anandamide metabolites are responsible for seizure protection. Consistent with this finding, arachidonic acid, a direct metabolite of anandamide, protects against seizures. To identify downstream effectors, we test for a role of transient receptor potential (TRP) channels and find that the TRPV1 antagonist capsazepine blocks the protective effect of anandamide. Also, a targeted genetic screen of TRP channels identifies water witch as a mediator of protection by anandamide. Using a Drosophila model, we reveal the role of arachidonic acid in seizure protection and identify a cannabinoid-receptor-1/2-independent mechanism of endocannabinoid seizure protection.

Targeting the endocannabinoid system: a predictive, preventive, and personalized medicine-directed approach to the management of brain pathologies

Cannabis-inspired medical products are garnering increasing attention from the scientific community, general public, and health policy makers. A plethora of scientific literature demonstrates intricate engagement of the endocannabinoid system with human immunology, psychology, developmental processes, neuronal plasticity, signal transduction, and metabolic regulation. Despite the therapeutic potential, the adverse psychoactive effects and historical stigma, cannabinoids have limited widespread clinical application. Therefore, it is plausible to weigh carefully the beneficial effects of cannabinoids against the potential adverse impacts for every individual. This is where the concept of "personalized medicine" as a promising approach for disease prediction and prevention may take into the account. The goal of this review is to provide an outline of the endocannabinoid system, including endocannabinoid metabolizing pathways, and will progress to a more in-depth discussion of the therapeutic interventions by endocannabinoids in various neurological disorders.

Endocannabinoid System and Cannabinoid 1 Receptors in Patients With Pharmacoresistant Temporal Lobe Epilepsy and Comorbid Mood Disorders

Experimental evidence points out that the activation of the endocannabinoid system induces neuroprotective effects and reduces mood disorders. In the hippocampus of patients with mesial temporal lobe epilepsy (MTLE), studies indicated augmented cannabinoid 1 receptor (CB₁R) binding, in spite of its low mRNA and protein expressions. Although this situation suggests an enhanced CB₁R-induced neurotransmission in patients with MTLE, especially those with pharmacoresistant seizures, which present important neuronal damage and high comorbid mood disorders. The present study focused to investigate the status of CB₁R and the endocannabinoid system by obtaining CB₁R-induced G-protein signaling efficacy and measuring the tissue levels of endocannabinoids in the hippocampus and the temporal neocortex of patients with pharmacoresistant MTLE. Furthermore, the obtained results were correlated with comorbid anxiety and depression. The experiments revealed that patients with MTLE present increased CB₁R-induced G-protein signaling efficacy (Emax) as well as an augmented tissue content of anandamide and oleoylethanolamine and low 2-arachidonoylglycerol. Some of these changes were more evident in patients with MTLE without mood disorders. The current findings indicate that pharmacoresistant MTLE is associated with increased CB₁R-induced transductional mechanisms as well as augmented tissue content of specific endocannabinoids in the hippocampus and the temporal neocortex. The enhanced endocannabinoid neurotransmission may be involved in the absence of comorbid mood disorders in some patients with MTLE.

Cannabis sativa: Much more beyond Δ9-tetrahydrocannabinol

Cannabis is the most used illicit drug worldwide and its medicinal use is under discussion, being regulated in several countries. However, the psychotropic effects of Δ⁹-tetrahydrocannabinol (THC), the main psychoactive compound of Cannabis sativa, are of concern. Thus, the interest in the isolated constituents without psychotropic activity, such as cannabidiol (CBD) and cannabidivarin (CBDV) is growing. CBD and CBDV are lipophilic molecules with poor oral bioavailability and are mainly metabolized by cytochrome P450 (CYP450) enzymes. The pharmacodynamics of CBD is the best explored, being able to interact with diverse molecular targets, like cannabinoid receptors, G protein-coupled receptor-55, transient receptor potential vanilloid 1 channel and peroxisome proliferator-activated receptor-γ. Considering the therapeutic potential, several clinical trials are underway to study the efficacy of CBD and CBDV in different pathologies, such as neurodegenerative diseases, epilepsy, autism spectrum disorders and pain conditions. The anti-cancer properties of CBD have also been demonstrated by several pre-clinical studies in different types of tumour cells. Although less studied, CBDV, a structural analogue of CBD, is receiving attention in the last years. CBDV exhibits anticonvulsant properties and, currently, clinical trials are underway for the treatment of autism spectrum disorders. Despite the benefits of these phytocannabinoids, it is important to highlight their potential interference with relevant physiologic mechanisms. In fact, CBD interactions with CYP450 enzymes and with drug efflux transporters may have serious consequences when co-administered with other drugs. This review summarizes the therapeutic advances of CBD and CBDV and explores some aspects of their pharmacokinetics, pharmacodynamics and possible interactions. Moreover, it also highlights the therapeutic potential of CBD and CBDV in several medical conditions and clinical applications.

Fatty Acid Amides Synthesized from Andiroba Oil (Carapa guianensis Aublet.) Exhibit Anticonvulsant Action with Modulation on GABA-A Receptor in Mice: A Putative Therapeutic Option

Epilepsy is a chronic neurological disease characterized by excessive neuronal activity leading to seizure; about 30% of affected patients suffer from the refractory and pharmacoresistant form of the disease. The anticonvulsant drugs currently used for seizure control are associated with adverse reactions, making it important to search for more effective drugs with fewer adverse reactions. There is increasing evidence that endocannabinoids can pharmacologically modulate action against seizure and antiepileptic disorders. Therefore, the objective of this study is to investigate the anticonvulsant effects of fatty acid amides (FAAs) in a pentylenetetrazole (PTZ)-induced seizure model in mice. FAAs (FAA1 and FAA2) are obtained from Carapa guianensis oil by biocatalysis and are characterized by Fourier Transform Infrared Analysis (FT-IR) and Gas Chromatography-Mass Spectrometry (GC-MS). Only FAA1 is effective in controlling the increased latency time of the first myoclonic jerk and in significantly decreasing the total duration of tonic-clonic seizures relative to the pentylenetetrazol model. Also, electrocortical alterations produced by pentylenetetrazol are reduced when treated by FAA1 that subsequently decreased wave amplitude and energy in Beta rhythm. The anticonvulsant effects of FAA1 are reversed by flumazenil, a benzodiazepine antagonist on Gamma-Aminobutyric Acid-A (GABA-A) receptors, indicating a mode of action via the benzodiazepine site of these receptors. To conclude, the FAA obtained from C. guianensis oil is promising against PTZ-induced seizures.

Epileptic Spikes in EEG and Migraine Attacks in the Course of Cannabis Withdrawal: A Case Report

In psychiatry, routine EEGs are often abnormal and not very specific, raising questions about the clinical relevance and consequences of potential anomalies. One such question is whether the administration of anticonvulsants would be useful if epileptic discharges are detected in patients without any clinical correlates. With regard to this question, we present a case study in which abnormal EEG patterns were observed in a patient with chronic migraine and cannabis addiction. The patient was a 34-year-old woman with a 14-year history of cannabis abuse who, during withdrawal, showed epileptic spikes, without any corresponding clinical symptoms, and migraine attacks of increasing intensity and frequency. This case study is in line with the new DSM-5 diagnostic tool that for the first time includes the diagnosis of cannabis withdrawal.