Anticonvulsant Action and Long-Term Effects of Chronic Cannabidiol Treatment in the Rat Pentylenetetrazole-Kindling Model of Epilepsy

Presynaptic antiseizure medications - basic mechanisms and clues for their rational combinations

Among clinically highly efficient antiseizure medications (ASMs) there are modifiers of the presynaptic release machinery. Of them, levetiracetam and brivaracetam show a high affinity to the synaptic vesicle protein type 2 A (SV2A), whereas pregabalin and gabapentin are selective ligands for the α2δ1 subunits of the voltage-gated calcium channels. In this paper, we present recent progress in understanding the significance of presynaptic release machinery in the neurochemical mechanisms of epilepsy and ASMs. Furthermore, we discuss whether the knowledge of the basic mechanisms of the presynaptically acting ASMs might help establish a rational polytherapy for drug-resistant epilepsy.

Melatonin improves cognitive dysfunction and decreases gliosis in the streptozotocin-induced rat model of sporadic Alzheimer's disease

Introduction

Alzheimer's disease (AD) and other forms of dementia have a devastating effect on the community and healthcare system, as neurodegenerative diseases are causing disability and dependency in older population. Pharmacological treatment options are limited to symptomatic alleviation of cholinergic deficit and accelerated clearance of β-amyloid aggregates, but accessible disease-modifying interventions are needed especially in the early phase of AD. Melatonin was previously demonstrated to improve cognitive function in clinical setting and experimental studies also.

Methods

In this study, the influence of melatonin supplementation was studied on behavioral parameters and morphological aspects of the hippocampus and amygdala of rats. Streptozotocin (STZ) was injected intracerebroventricularly to induce AD-like symptoms in male adult Wistar rats (n = 18) which were compared to age-matched, sham-operated animals (n = 16). Melatonin was administered once daily in a dose of 20 mg/kg body weight by oral route. Behavioral analysis included open-field, novel object recognition, and radial-arm maze tests. TNF-α and MMP-9 levels were determined from blood samples to assess the anti-inflammatory and neuroprotective effects of melatonin. Immunohistological staining of brain sections was performed using anti-NeuN, anti-IBA-1, and anti-GFAP primary antibodies to evaluate the cellular reorganization of hippocampus.

Results and Discussion

The results show that after 40 days of treatment, melatonin improved the cognitive performance of STZ-induced rats and reduced the activation of microglia in both CA1 and CA3 regions of the hippocampus. STZ-injected animals had higher levels of GFAP-labeled astrocytes in the CA1 region, but melatonin treatment reduced this to that of the control group. In conclusion, melatonin may be a potential therapeutic option for treating AD-like cognitive decline and neuroinflammation.

Cholecalciferol Supplementation Impacts Behavior and Hippocampal Neuroglial Reorganization in Vitamin D-Deficient Rats

Vitamin D deficiency (VDD) is widespread around the world and has been extensively documented to affect various health conditions, including the cognitive functioning of the brain. Serum 25-hydroxylated forms of vitamin D are traditionally used to determine vitamin D status. However, there is now evidence that cholecalciferol activation can occur and be controlled by locally expressed enzymes in the brain. This study aimed to investigate the effects of cholecalciferol supplementation on cognitive function in rats who underwent transient VDD in adulthood. Thirty-six adult Wistar rats were administered paricalcitol (seven doses of 32 ng injected every other day) along with a "vitamin D-free" diet to induce VDD, which was confirmed using a LC-MS/MS serum analysis of the cholecalciferol and 25-hydroxyvitamin D3 levels. Treatment was performed by including 1000 IU/kg and 10,000 IU/kg cholecalciferol in the diet. Cognitive performance was evaluated using the novel object recognition (NOR), Morris water maze (MWM), and radial arm maze (RAM) tests. An immunohistochemical analysis of the brain regions involved in learning and memory was performed by quantifying the neurons, astrocytes, and microglia labelled with anti-neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba-1) antibodies, respectively. The vitamin D deficient group showed the lowest performance in both the MWM and RAM tests. In contrast, the cholecalciferol-treated groups exhibited a faster learning curve. However, no difference was detected between the groups in the NOR test. On the other hand, differences in the cellular organization of the hippocampus and amygdala were observed between the groups. Cholecalciferol supplementation decreased the density of the Iba-1- and GFAP-labeled cells in the hilus and cornu Ammonis 3 (CA3) regions of the hippocampus and in the amygdala. These results support vitamin D's substantial role in learning and memory. They also highlight that subtle changes of cognitive function induced by transient VDD could be reversed by cholecalciferol supplementation. Further studies are needed to better understand VDD and cholecalciferol's effects on the brain structure and function.

Cannabidiol Anticonvulsant Effects Against Lithium-Pilocarpine-Induced Status Epilepticus in Male Rats Are Mediated by Neuroinflammation Modulation and Cannabinoids 1 (CB1), But Not CB2 and GABAA Receptors

Background: Status epilepticus (SE) is a series of seizures that can lead to serious neurological damages. Cannabidiol (CBD) is extracted from the cannabis plant, which has been approved as an antiseizure medication. This study aimed to determine the efficacy of various doses of CBD on lithium-pilocarpine-induced SE in rats and possible involvement of multiple pharmacological pathways. We hypothesized that cannabinoid receptors type 1 (CB1) and CB2, as well as GABAA receptors, might have important roles in the anticonvulsant effects of CBD against SE by its anti-inflammatory effects. Methods: SE was induced by intraperitoneal (i.p.) injection of lithium (127 mg/kg, i.p.) and pilocarpine (60 mg/kg, i.p., 20 h after lithium). Forty-two male rats were divided into seven groups (including control and sham groups), and the treated groups received different doses of CBD (1, 3, 5, 10, and 25 mg/kg, i.p.). SE score was recorded over the next 2 h following pilocarpine injection. Then, we measured the levels of pro-inflammatory cytokines, including interleukin (IL)-lβ and tumor necrosis factor (TNF)-α, using ELISA kits. Also we analyzed the expression of CB1, CB2, and GABAA receptors using the Western blot technique. Results: CBD at 5 mg/kg significantly reduced Racine's scale and duration of seizures, and increased the onset time of seizure. Moreover, CBD 5 mg/kg caused significant reductions in the elevated levels of IL-lβ and TNF-α, as well as a significant increase in the decreased level of CB1 receptor expression compared to the control group. In other word, CBD reverted the effects of SE in terms of neuroinflammation and CB1 receptor. Based on the obtained results, CBD was not able to restore the declined levels of CB2 or GABAA receptors. Conclusion: Our study found anticonvulsant effects of CBD on the SE rat model induced by lithium-pilocarpine with probable involvement of CB1 receptors and anti-inflammatory effects by reducing IL-1β and TNF-α markers independent of CB2 and GABAA receptors.

Barbaloin Protects Pentylenetetrazol-Induced Cognitive Deficits in Rodents via Modulation of Neurotransmitters and Inhibition of Oxidative-Free-Radicals-Led Inflammation

BACKGROUND

Epilepsy is defined by an excessive level of activity in the neurons and coordinated bursts of electrical activity, resulting in the occurrence of seizure episodes. The precise cause of epileptogenesis remains uncertain; nevertheless, the etiology of epilepsy may involve neuroinflammation, oxidative stress, and malfunction of the neurotransmitter system.

OBJECTIVE

The goal of this investigation was to assess barbaloin's protective properties with respect to pentylenetetrazol (PTZ)-)-induced cognitive deficits in rats via antioxidative, anti-inflammatory, and neurotransmitter-modulating effects.

METHODS

Wistar rats were subjected to PTZ [40 mg/kg (i.p.)], which induced cognitive decline. Behavior assessment using a kindling score, open-field test (OFT), novel object recognition test (NORT), and assays for superoxide dismutase (SOD), reduced glutathione (GSH), catalase (CAT), malondialdehyde (MDA), acetylcholinesterase (AChE), caspase-3, nitric oxide (NO), interleukins-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-6, nuclear factor kappa-B (NF-κB), Bcl-2 and Bax, and neurotransmitter levels [GABA, DA, NE, and serotonin (5-HT)] were performed.

RESULTS

The treatment of rats with barbaloin resulted in behavior improvement and significant changes in the levels of GSH, SOD, CAT, MDA, AChE, NO, IL-6, IL-1β, TNF-α, NF-κB, caspase-3, Bcl-2, and Bax compared to the PTZ control group. Barbaloin treatment resulted in notable changes in neurotransmitter levels (GABA, NE, 5-HT, DA) compared to the PTZ group.

CONCLUSIONS

The ongoing study has gathered evidence indicating that the injection of barbaloin has resulted in significant improvements in cognitive performance in rats. This is achieved by inhibiting oxidative stress, enhancing the activity of natural antioxidant enzymes, reducing cytokine levels, and increasing the levels of neurotransmitters in the brain. These results were detected in comparison to a PTZ control and can be attributed to the potent anti-inflammatory and antioxidant capabilities of barbaloin, which could be linked to its neuroprotective properties. Barbaloin may potentially increase cognitive decline and boost neuronal survival by altering the expression of Bax, caspase-3, Bcl-2.

Cannabidiol Modifies the Glutamate Over-Release in Brain Tissue of Patients and Rats with Epilepsy: A Pilot Study

Drug-resistant epilepsy (DRE) is associated with high extracellular levels of glutamate. Studies support the idea that cannabidiol (CBD) decreases glutamate over-release. This study focused on investigating whether CBD reduces the evoked glutamate release in cortical synaptic terminals obtained from patients with DRE as well as in a preclinical model of epilepsy. Synaptic terminals (synaptosomes) were obtained from the epileptic neocortex of patients with drug-resistant temporal lobe epilepsy (DR-TLE, n = 10) or drug-resistant extratemporal lobe epilepsy (DR-ETLE, n = 10) submitted to epilepsy surgery. Synaptosomes highly purified by Percoll-sucrose density gradient were characterized by confocal microscopy and Western blot. Synaptosomes were used to estimate the high KCl (33 mM)-evoked glutamate release in the presence of CBD at different concentrations. Our results revealed responsive tissue obtained from seven patients with DR-TLE and seven patients with DR-ETLE. Responsive tissue showed lower glutamate release (p < 0.05) when incubated with CBD at low concentrations (less than 100 µM) but not at higher concentrations. Tissue that was non-responsive to CBD (DR-TLE, n = 3 and DR-ELTE, n = 3) showed high glutamate release despite CBD exposure at different concentrations. Simultaneously, a block of the human epileptic neocortex was used to determine its viability through whole-cell and extracellular electrophysiological recordings. The electrophysiological evaluations supported that the responsive and non-responsive human epileptic neocortices used in the present study exhibited proper neuronal viability and stability to acquire electrophysiological responses. We also investigated whether the subchronic administration of CBD could reduce glutamate over-release in a preclinical model of temporal lobe epilepsy. Administration of CBD (200 mg/kg, p.o. every 24 h for 7 days) to rats with lithium-pilocarpine-evoked spontaneous recurrent seizures reduced glutamate over-release in the hippocampus. The present study revealed that acute exposure to low concentrations of CBD can reduce the glutamate over-release in synaptic terminals obtained from some patients with DRE. This effect is also evident when applied subchronically in rats with spontaneous recurrent seizures. An important finding was the identification of a group of patients that were non-responsive to CBD effects. Future studies are essential to identify biomarkers of responsiveness to CBD to control DRE.

Effects of the Acute and Chronic Administration of Cannabidiol on Cognition in Humans and Animals: A Systematic Review

Introduction: The effects of cannabidiol (CBD) on cognition has been investigated in recent years to determine the therapeutic potential of this cannabinoid for a broad gamut of medical conditions, including neuropsychiatric disorders. The aim of the present study was to perform a systematic review of studies that analyzed the effects of the acute and chronic administration of CBD on cognition in humans and animals both to assess the cognitive safety of CBD and to determine a beneficial potential of CBD on cognition. Methods: The PubMed, Web of Science, PsycINFO, and Scopus databases were searched in December of 2022 for relevant articles using the following combinations of keywords: ("cannabidiol" OR "CBD") AND ("cognition" OR "processing cognitive" OR "memory" OR "language" OR "attention" OR "executive function" OR "social cognition" OR "perceptual motor ability" OR "processing speed"). Results: Fifty-nine articles were included in the present review (36 preclinical and 23 clinical trials). CBD seems not to have any negative effect on cognitive processing in rats. The clinical trials confirmed these findings in humans. One study found that repeated dosing with CBD may improve cognitive in people who use cannabis heavily but not individuals with neuropsychiatric disorders. Considering the context of neuropsychiatric disorders in animal models, CBD seems to reverse the harm caused by the experimental paradigms, such that the performance of these animals becomes similar to that of control animals. Conclusions: The results demonstrate that the chronic and acute administration of CBD seems not to impair cognition in humans without neuropsychiatric disorders. In addition, preclinical studies report promising results regarding the effects of CBD on the cognitive processing of animals. Future double-blind, placebo-controlled, randomized clinical trials with larger, less selective samples, with standardized tests, and using different doses of CBD in outpatients are of particular interest to elucidate the cognitive effects of CBD.

Long-Term Treatment with Cannabidiol-Enriched Cannabis Extract Induces Synaptic Changes in the Adolescent Rat Hippocampus

The endocannabinoid system (eCS) is widely distributed in mammalian tissues and it is classically formed by cannabinoid receptors, endogenous bioactive lipids and its synthesis and degradation enzymes. Due to the modulatory role of eCS in synaptic activity in the Central Nervous System (CNS), phytocannabinoids have been increasingly used for the treatment of neurological disorders, even though little is known in terms of the long-term effect of these treatments on CNS development, mainly in the timeframe that comprises childhood and adolescence. Furthermore, an increased number of clinical trials using full-spectrum Cannabis extracts has been seen, rather than the isolated form of phytocannabinoids, when exploring the therapeutical benefits of the Cannabis plant. Thus, this study aims to evaluate the effect of cannabidiol (CBD)-enriched Cannabis extract on synaptic components in the hippocampus of rats from adolescence to early adulthood (postnatal day 45 to 60). Oral treatment of healthy male Wistar rats with a CBD-enriched Cannabis extract (3 mg/kg/day CBD) during 15 days did not affect food intake and water balance. There was also no negative impact on locomotor behaviour and cognitive performance. However, the hippocampal protein levels of GluA1 and GFAP were reduced in animals treated with the extract, whilst PSD95 levels were increased, which suggests rearrangement of glutamatergic synapses and modulation of astrocytic features. Microglial complexity was reduced in CA1 and CA3 regions, but no alterations in their phagocytic activity have been identified by Iba-1 and LAMP2 co-localization. Collectively, our data suggest that CBD-enriched Cannabis treatment may be safe and well-tolerated in healthy subjects, besides acting as a neuroprotective agent against hippocampal alterations related to the pathogenesis of excitatory and astrogliosis-mediated disorders in CNS.

Repeated Inhalation of Peppermint Essential Oil Improves Exercise Performance in Endurance-Trained Rats

Peppermint essential oil, being natural and safe, with antioxidant and anti-inflammatory properties, has long been a research interest in relieving fatigue and improving exercise performance. However, the related studies report controversial results, and the mechanisms remain unclear. Here we found that inhalation of peppermint essential oil significantly extended the exhaustion time in rats subjected to 2-week weight-bearing swimming training. Sprague-Dawley rats were subjected to a 2-week weight-loaded forced swimming regimen. Prior to each swimming session, the rats were administered peppermint essential oil via inhalation. An exhaustive swimming test was performed at the end of the protocol. Rats treated with essential oil had significantly extended time to exhaustion compared with exercised rats without essential oil treatment. In addition, treated rats also showed reduced oxidative damage induced by endurance exercise. Notably, the rats receiving two-week essential oil inhalation while not subjected to swimming training did not show improved exercise performance. The findings demonstrate that repeated inhalation of peppermint essential oil enhances the effects of endurance training and improves exercise performance partially by preventing oxidative damage.

Special Issue: Therapeutic Potential for Cannabis and Cannabinoids

The number of patients reporting the use of cannabis for medical purposes, whether through state-regulated medical marijuana programs or through over-the-counter hemp extracts, continues to grow [...]

Cannabidiol reveals a disruptive strategy for 21st century epilepsy drug discovery

Over 30 antiseizure medicines (ASMs) have been uncovered in a diversity of preclinical seizure and epilepsy models, with several critical inflection points in the 20th century fundamentally transforming ASM discovery. This commentary aims to review the historical relevance of cannabidiol's (CBD; Epidiolex) approval for epilepsy in the context of other ASMs brought to market. Further, we highlight how CBD's approval may represent an inflection point for 21st century ASM discovery. CBD is one of the main phytocannabinoids of Cannabis sativa. Unlike its related phytocannabinoid, Δ9-tetrahydrocannabinol, CBD does not exert any euphorigenic, tolerance, or withdrawal effects at anticonvulsant doses. CBD also possess marked anti-inflammatory effects, offering the tantalizing potential of a new pharmacological approach in epilepsy. For decades, hints of the anticonvulsant profile of CBD had been suggested with a small handful of studies in rodent seizure models, yet difficulties in formulation, compounded by the social and regulatory pressures related to medical use of cannabis plant-derived agents constrained any clinical implementation. Nonetheless, CBD possesses a broad antiseizure profile in preclinical seizure and epilepsy models, but the transformative impact of CBD'-s approval came because of studies in a rodent model of the orphan disease Dravet syndrome (DS). DS is a pediatric developmental epileptic encephalopathy with high mortality, frequent spontaneous recurrent seizures, and marked resistance to conventional ASMs, such as phenytoin and carbamazepine. CBD was approved for DS by the US Food and Drug Administration in 2018 after convincing efficacy was established in randomized, placebo-controlled trials in children. Because of the clinical approval of CBD as a novel, cannabis plantderived ASM for DS, CBD has revealed a new strategy in ASM discovery to reignite 21st century therapeutic development for epilepsy. In this commentary, we review the major preclinical and clinical milestones of the late 20th century that made CBD, a compound historically subjected to regulatory restrictions, a key driver of a new discovery strategy for epilepsy in the 21st century.

Antibiotics modulate frequency and early generation of epileptic seizures in zebrafish

Antibiotics have been used for decades to treat various bacterial infections. Apart from bactericidal activities, their potential side effects have not been much studied or evaluated. Neurotoxicity is a major concern in the case of β-lactam and fluoroquinolone families, which can result in convulsions or seizures. Here, we proposed a hypothesis to check whether antibiotic treatment can conclusively enhance anxiety-like behaviours and how seizure behavioural profile gets modulated in pentylenetetrazole (PTZ)-treated zebrafish. Zebrafish were treated with selected antibiotics such as 25 mg/L Penicillin G (PG) and Ciprofloxacin (CPFX), for 7 days and thereafter exposed to PTZ (7.5 mM) for 20 min. The data indicate that PG and CPFX-treated groups exhibited anxiety-like or stressed behavioural phenotypes in the novel tank test (6 min), and also, they were found to promote hyperactivity. Early onset of PTZ-induced seizure-like behavioural scores, the heightened intensity of seizure and reduced latency in different scores were found in PG and CPFX-administered groups. This study substantiates that PG and CPFX as potential seizure modulators in zebrafish. The zebrafish is a well-established and still expanding model organism in many fields. Here, we again reinforce zebrafish as a prominent model to investigate seizure-like neuro-behavioural entities and confirm that chronic antibiotic use has negative consequences that can exacerbate the circumstances of vertebrate species exhibiting seizure-related reactions.