Epileptogenic effect of cyclosporine in guinea-pig hippocampal slices

Sustained consumption of cocoa-based dark chocolate enhances seizure-like events in the mouse hippocampus

While the consumption of caffeine and cocoa has been associated with a variety of health benefits to humans, some authors have proposed that excessive caffeine intake may increase the frequency of epileptic seizures in humans and reduce the efficiency of antiepileptic drugs. Little is known, however, about the proconvulsant potential of the sustained, excessive intake of cocoa on hippocampal neural circuits. Using the mouse as an experimental model, we examined the effects of the chronic consumption of food enriched in cocoa-based dark chocolate on motor and mood-related behaviours as well as on the excitability properties of hippocampal neurons. Cocoa food enrichment did not affect body weights or mood-related behaviours but rather promoted general locomotion and improved motor coordination. However, ex vivo electrophysiological analysis revealed a significant enhancement in seizure-like population spike bursting at the neurogenic dentate gyrus, which was paralleled by a significant reduction in the levels of GABA-α1 receptors thus suggesting that an excessive dietary intake of cocoa-enriched food might alter some of the synaptic elements involved in epileptogenesis. These data invite further multidisciplinary research aiming to elucidate the potential deleterious effects of chocolate abuse on behaviour and brain hyperexcitability.

[Ciclosporin-associated cerebral tumor-like location of Behçet's disease]

INTRODUCTION

Cerebral tumor-like location is uncommon in the course of Behçet's disease. We report herein a patient with tumor-like lesions associated with ciclosporin therapy.

CASE REPORT

A 45-year-old male treated for 17 years with colchicine and ciclosporin for Behçet's disease with cutaneomucosal, ocular and joint involvement was admitted for sudden onset of meningo-encephalitis with lymphocytic meningitis. CT-scan showed a nodular lesion of the brainstem enhanced by iodine. Ciclosporin was discontinued; prednisone and IV cyclophosphamide were started. After three months of favorable outcome, a relapse occurred when ciclosporin was started again. MRI showed two additional capsulothalamic lesions. Prednisone and cyclophosphamide were started again with a favorable response and minimal sequelae.

CONCLUSION

The main challenge in cerebral tumor-like location of Behçet's disease is to rule out other inflammatory or tumor processes. Neuronal toxicity of ciclosporin limits indications for this therapy in Behçet's disease.

[Neurological complications of inflammatory bowel disease]

Although ulcerative colitis and Crohn's disease have traditionally been considered to be inflammatory diseases limited to the gastrointestinal tract, it has been shown that both pathologies are frequently accompanied by various extraintestinal disorders. There is an increasing evidence that they may also manifest in the nervous system, including the peripheral and the central parts. Although some of these neurological complications have been known for a long time, such as cerebrovascular disease, vasculitis and autoinmune processes including neuropathies and cerebral demyelination, others have been recently described. With the exception of some of this complications such as the thromboembolism, evidence for a casual relationship relies merely on single case reports or case series. In this article, we try to review the existing evidence on neurological manifestations of both variants of inflammatory bowel disease.

Glutamate and dopamine receptors contribute to the lateral spread of epileptiform discharges in rat neocortical slices

PURPOSE

The effects of AMPA-type glutamate receptor as well as dopamine D1 and D2 receptors on the lateral propagation of epileptiform field potentials (EFP) were studied across adjacent areas of rat neocortical tissues.

METHODS

Epileptiform burst discharges were induced by superfusion of Mg(2+)-free artificial cerebrospinal fluid. Simultaneous field potential recordings of EFP were obtained from four microelectrodes placed 2-3 mm apart across coronal slices in the third layer of the neocortex. The effects of AMPA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), dopamine D1 receptor agonist SKF 81297, and dopamine D2 receptor agonist quinpirole on lateral propagation of burst discharges were investigated.

RESULTS

CNQX, applied focally between recording sites, blocked rapid propagation across treated areas and resulted in the emergence of spatially separate, independent pacemakers. Focal application of SKF 81297 between recording sites increased the repetition rate of EFP, but reduced the amplitude as well as the duration of epileptic discharges. However, addition of SKF 81297 to the bath medium abolished EFP. Both local and systemic applications of quinpirole irreversibly enhanced repetition rate of epileptiform burst discharges.

CONCLUSIONS

The results indicate the prerequisite of AMPA synaptic transmission for synchronized lateral propagation of Mg(2+)-free ACSF-induced epileptic activity and the modulatory effects of dopamine D1 and D2 receptors on both EFP initiation and propagation in epileptic tissues.

Rapamycin: brain excitability studied in vitro

Neurological complications are common in transplant recipients treated with immunosuppressant calcineurin inhibitors. Rapamycin, a macrolide antibiotic, was suggested as an alternative agent in patients who develop calcineurin inhibitor associated neurotoxicity, including seizure attacks. The aim of the present study was to test the effect of rapamycin on the bioelectrical activity and evoked field excitatory postsynaptic potentials (fEPSP) in CA1 area of hippocampal tissues and compare its effect with FK506, a calcineurin inhibitor agent. Application of rapamycin at different concentrations neither affected the bioelectrical activity nor changed fEPSP magnitude. In contrast, FK506 elicited epileptiform burst discharges and significantly enhanced fEPSP magnitude. This study supports the suggestion that rapamycin could be used as an alternative to calcineurin inhibitors in the event of neurotoxicity.

Mitochondrial calcium ion and membrane potential transients follow the pattern of epileptiform discharges in hippocampal slice cultures

Emerging evidence suggests that mitochondrial dysfunction contributes to the pathophysiology of epilepsy. Recurrent mitochondrial Ca2+ ion load during seizures might act on mitochondrial membrane potential (DeltaPsim) and proton motive force. By using electrophysiology and confocal laser-scanning microscopy, we investigated the effects of epileptiform activity, as induced by low-Mg2+ ion perfusion in hippocampal slice cultures, on changes in DeltaPsim and in mitochondrial Ca2+ ion concentration ([Ca2+]m). The mitochondrial compartment was identified by monitoring DeltaPsim in the soma and dendrites of patched CA3 pyramidal cells using the mitochondria-specific voltage-sensitive dye rhodamine-123 (Rh-123). Interictal activity was accompanied by localized mitochondrial depolarization that was restricted to a few mitochondria in small dendrites. In contrast, robust Rh-123 release into the cytosol was observed during seizure-like events (SLEs), indicating simultaneous depolarization of mitochondria. This was critically dependent on Ca2+ ion uptake and extrusion, because inhibition of the mitochondrial Ca2+ ion uniporter by Ru360 and the mitochondrial Na+/Ca2+ ion exchanger by 7-chloro-5-(2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one but not the inhibitor of mitochondrial permeability transition pore, cyclosporin A, decreased the SLE-associated mitochondrial depolarization. The Ca2+ ion dependence of simultaneous mitochondrial depolarization suggested enhanced Ca2+ ion cycling across mitochondrial membranes during epileptiform activity. Indeed, [Ca2+]m fluctuated during interictal activity in single dendrites, and these fluctuations spread over the entire mitochondrial compartment during SLEs, as revealed using mitochondria-specific dyes (rhod-2 and rhod-ff) and spatial frequency-based image analysis. These findings strengthen the hypothesis that epileptic activity results in Ca2+ ion-dependent changes in mitochondrial function that might contribute to the neuronal injury during epilepsy.

Hippocampal neurotransplantation evaluated in the rat kainic acid epilepsy model

OBJECTIVE

Neurotransplantation has focused on disorders that involve subcortical brain targets. We evaluated the concepts of epileptic focus repair and changes in animal behavior through replacement of lost hippocampal neurons. The safety of hippocampal neurotransplantation was assessed in the rat kainic acid (KA) epilepsy model.

METHODS

Sixty-three rats were studied and classified into six groups: KA plus 40,000 LBS-Neurons (Layton BioScience, Sunnyvale, CA; n = 13); KA plus 80,000 cells (n = 12); KA plus media (n = 9); no-KA plus 40,000 cells (n = 12); no-KA plus 80,000 cells (n = 12); and no-KA plus media (n = 5). Clinical observation (2 h daily) and electroencephalogram recording (3 h every other week) were performed to check for seizures until Week 11 after KA injection. On Week 12, the Morris water maze test was performed to assess spatial learning and memory.

RESULTS

Four rats were excluded because of intracranial hematoma or abscess. In the clinical observation of seizures, the no-KA plus media group had significantly fewer seizures than rats that received KA followed by injection of 40,000 cells, 80,000 cells, or media (P = 0.001, 0.0004, and 0.004, respectively). On electroencephalographic analysis, there was no significant difference between any of the groups. Transplanted rats with KA-induced epilepsy did not have an increased number of seizures. In the Morris water maze test, the hidden platform task showed that the KA plus 80,000 cell group had significantly longer swim latencies than groups with no-KA plus 40,000 cells (P = 0.035) or no-KA plus 80,000 cells (P = 0.015), demonstrating the behavioral deficits caused by KA injection. The probe trial showed no significant difference for the percentage of time in the target quadrant between any of the groups. Histological studies showed that 26 (59%) of 44 transplanted rats had evidence of graft survival.

CONCLUSION

The safety of cortical neurotransplantation was demonstrated, even in an animal model predisposed to epilepsy. We did not find evidence for cessation of seizures or improvement in behavior using this model.