Study of spontaneous recurrent seizures and morphological alterations after status epilepticus induced by intrahippocampal injection of pilocarpine

Epileptic seizures are clinical manifestations of neuronal discharges characterized by hyperexcitability and/or hypersynchrony in the cortex and other subcortical regions. The pilocarpine (PILO) model of epilepsy mimics temporal lobe epilepsy (TLE) in humans. In the present study, we used a more selective approach: microinjection of PILO into the hilus of the dentate gyrus (H-PILO). Our main goal was to evaluate the behavioral and morphological alterations present in this model of TLE. Seventy-six percent of all animals receiving H-PILO injections had continuous seizures called status epilepticus (SE). A typical pattern of evolution of limbic seizures during the SE with a latency of 29.3 +/- 16.3 minutes was observed using an analysis of behavioral sequences. During the subsequent 30 days, 71% of all animals exhibited spontaneous recurrent seizures (SRSs) during a daily 8-hour videotaping session. These SRSs had a very conspicuous and characteristic pattern detected by behavioral sequences or neuroethological analysis. Only the animals that had SE showed positive Neo-Timm staining in the inner molecular layer of the dentate gyrus (sprouting) and reduced cell density in Ammon`s horn pyramidal cell subfield CA1. However, no correlation between the intensity of sprouting and the mean number and total number of SRSs was found. Additionally, using Fluoro-Jade staining, we observed neurodegeration in the hilus and pyramidal cell subfields CA3 and CM 24 hours after SE. These data indicate that H-PILO is a reliable, selective, efficient, low-mortality model that mimics the acute and chronic behavioral and morphological aspects of TLE. (C) 2010 Elsevier Inc. All rights reserved.

The renin-angiotensin system is upregulated in the cortex and hippocampus of patients with temporal lobe epilepsy related to mesial temporal sclerosis

Purpose: As reported by several authors, angiotensin II (AngII) is a proinflammatory molecule that stimulates the release of inflammatory cytokines and activates nuclear factor kappa B (NF kappa B), being also associated with the increase of cellular oxidative stress. Its production depends on the activity of the angiotensin converting enzyme (ACE) that hydrolyzes the inactive precursor angiotensin I (AngI) into AngII. It has been suggested that AngII underlies the physiopathological mechanisms of several brain disorders such as stroke, bipolar disorder, schizophrenia, and disease. The aim of the present work was to localize and quantify AngII AT1 and AT2 receptors in the cortex and hippocampus of patients with temporal lobe epilepsy related to mesial temporal sclerosis (MTS) submitted to corticoamygdalohippocampectomy for seizure control. Method: Immunohistochemistry, Western blot, and real-time PCR techniques were employed to analyze the expression of these receptors. Results: The results showed an upregulation of AngII AT1 receptor as well as its messenger ribonucleic acid (mRNA) expression in the cortex and hippocampus of patients with MTS. In addition, an increased immunoexpression of AngII AT2 receptors was found only in the hippocampus of these patients with no changes in its mRNA levels. Discussion: These data show, for the first time, changes in components of renin-angiotensin system (RAS) that could be implicated in the physiopathology of MTS.

Modulation of B-1 and B-2 kinin receptors expression levels in the hippocampus of rats after audiogenic kindling and with limbic recruitment, a model of temporal lobe epilepsy

Epileptic seizures are hypersynchronous, paroxystic and abnormal neuronal discharges. Epilepsies are characterized by diverse mechanisms involving alteration of excitatory and inhibitory neurotransmission that result in hyperexcitability of the central nervous system (CNS). Enhanced neuronal excitability can also be achieved by inflammatory processes, including the participation of cytokines, prostaglandins or kinins, molecules known to be involved in either triggering or in the establishment of inflammation. Multiple inductions of audiogenic seizures in the Wistar audiogenic rat (WAR) strain are a model of temporal lobe epilepsy (TLE), due to the recruitment of limbic areas such as hippocampus and amygdata. In this study we investigated the modulation of the B-1 and B-2 kinin receptors expression levels in neonatal WARs as well as in adult WARs subjected to the TLE model. The expression levels of pro-inflammatory (IL-1 beta) and anti-inflammatory (IL-10) cytokines were also evaluated, as well as cyclooxygenase (COX-2). Our results showed that the B-1 and B-2 kinin receptors mRNAs were up-regulated about 7- and 4-fold, respectively, in the hippocampus of kindled WARs. On the other hand, the expressions of the IL-1 beta, IL-10 and COX-2 were not related to the observed increase of expression of kinin receptors. Based on those results we believe that the B, and B2 kinin receptors have a pivotal role in this model of TLE, although their participation is not related to an inflammatory process. We believe that kinin receptors in the CNS may act in seizure mechanisms by participating in a specific kininergic neurochemical pathway. (c) 2007 Elsevier B.V. All rights reserved.

Acoustic hypersensitivity in adult rats after neonatal ventral hippocampus lesions

Rats with a bilateral neonatal ventral hippocampus lesion (NVHL) are used as models of neurobiological aspects of schizophrenia. In view of their decreased number of GABAergic interneurons, we hypothesized that they would show increased reactivity to acoustic stimuli. We systematically characterized the acoustic reactivity of NVHL rats and sham operated controls. They were behaviourally observed during a loud white noise. A first cohort of 7 months` old rats was studied. Then the observations were reproduced in a second cohort of the same age after characterizing the reactivity of the same rats to dopaminergic drugs. A third cohort of rats was studied at 2, 3, 4, 5 and 6 months. In subsets of lesioned and control rats, inferior colliculus auditory evoked potentials were recorded. A significant proportion of rats (50-62%) showed aberrant audiogenic responses with explosive wild running resembling the initial phase of audiogenic seizures. This was not correlated with their well-known enhanced reactivity to dopaminergic drugs. The proportion of rats showing this strong reaction increased with rats` age. After the cessation of the noise, NVHL rats showed a long freezing period that did neither depend on the size of the lesion nor on the rats` age. The initial negative deflection of the auditory evoked potential was enhanced in the inferior colliculus of only NVHL rats that displayed wild running. Complementary anatomical investigations using X-ray scans in the living animal, and alizarin red staining of brain slices, revealed a thin layer of calcium deposit close to the medial geniculate nuclei in post-NVHL rats, raising the possibility that this may contribute to the hyper-reactivity to sounds seen in these animals. The findings of this study provide complementary information with potential relevance for the hyper-reactivity noted in patients with schizophrenia, and therefore a tool to investigate the underlying biology of this endophenotype. (C) 2009 Elsevier B.V. All rights reserved.

Expression of vitamin D receptor mRNA in the hippocampal formation of rats submitted to a model of temporal lobe epilepsy induced by pilocarpine

Vitamin D (VD), is a steroid hormone with multiple functions in the central nervous system (CNS), producing numerous physiological effects mediated by its receptor (VDR). Clinical and experimental studies have shown a link between VD dysfunction and epilepsy. Along these lines, the purpose of our work was to analyze the relative expression of VDR mRNA in the hippocampal formation of rats during the three periods of pilocarpine-induced epilepsy. Male Wistar rats were divided into five groups: (1) control group; rats that received saline 0.9%, i.p. and were killed 7 days after its administration (CTRL, n = 8), (2) SE group; rats that received pilocarpine and were killed 4 h after SE (SE, n = 8), (3) Silent group-7 days; rats that received pilocarpine and were killed 7 days after SE (SIL 7d, n = 8), (4) Silent group-14 days; rats that received pilocarpine and were killed 14 days after SE (SIL 14d, n = 8), (5) Chronic group; rats that received pilocarpine and were killed 60 days after the first spontaneous seizure, (chronic, n = 8). The relative expression of VDR mRNA was determined by real-time PCR. Our results showed an increase of the relative expression of VDR mRNA in the SIL 7 days, SIL 14 days and Chronic groups, respectively (0.060 +/- 0.024; 0.052 +/- 0.035; 0.085 +/- 0.055) when compared with the CTRL and SE groups (0.019 +/- 0.017; 0.019 +/- 0.025). These data suggest the VDR as a possible candidate participating in the epileptogenesis process of the pilocarpine model of epilepsy. (C) 2008 Elsevier Inc. All rights reserved.

From lateral to mesial: The quest for a surgical cure for temporal lobe epilepsy

Purpose: A gap of more than a hundred years occurred between the first accounts of mesial temporal sclerosis and recognition of its role in the pathogenesis of psychomotor seizures. This paper reviews how the understanding and surgical treatment of temporal lobe epilepsy developed, particularly from the work of Penfield, Jasper, and their associates at the Montreal Neurological Institute (MNI). Methods: Publications on EEG and surgery for temporal lobe seizures from 1935 to 1953 were reviewed and charts of selected patients operated on at the MNI in the same period were examined. Attention was focused on the evolution of surgical techniques for temporal lobe epilepsy. Results: In the late 1930s, some EEG findings suggested deep-lying disturbances originating in the temporal lobe. However, it took another two decades before the correlation of clinical, neurophysiological, and anatomical findings provided evidence for the involvement of the mesial structures in psychomotor or temporal lobe seizures. From 1949 and onward, Penfield and his associates applied this evidence to extend the surgical resections to include the uncus and the hippocampus. Conclusion: The collaborative work of a team led by Penfield and Jasper at the MNI helped to define the role of neurophysiological studies in epilepsy surgery. As a result, the importance of removing the mesial structures in order to obtain better seizure control in patients with temporal lobe epilepsy became firmly established.

(1)H magnetic resonance spectroscopy imaging of the hippocampus in patients with panic disorder

Recent theories of panic disorder propose an extensive involvement of limbic system structures, such as the hippocampus, in the pathophysiology of this condition. Despite this, no prior study has examined exclusively the hippocampal neurochemistry in this disorder. The current study used proton magnetic resonance spectroscopy imaging ((1)H-MRSI) to examine possible abnormalities in the hippocampus in panic disorder patients. Participants comprised 25 panic patients and 18 psychiatrically healthy controls. N-acetylaspartate (NAA, a putative marker of neuronal viability) and choline (Cho, involved in the synthesis and degradation of cell membranes) levels were quantified relative to creatine (Cr, which is thought to be relatively stable among individuals and in different metabolic condition) in both right and left hippocampi. Compared with controls, panic patients demonstrated significantly lower NAA/Cr in the left hippocampus. No other difference was detected. This result is consistent with previous neuroimaging findings of hippocampal alterations in panic and provides the first neurochemical evidence suggestive of involvement of this structure in the disorder. Moreover, lower left hippocampal NAA/Cr in panic disorder may possibly reflect neuronal loss and/or neuronal metabolic dysfunction, and could be related to a deficit in evaluating ambiguous cues. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Equivalent Neurogenic Potential of Wild-Type and GFP-Labeled Fetal-Derived Neural Progenitor Cells Before and After Transplantation Into the Rodent Hippocampus

Introduction. The hippocampal formation is a specific structure in the brain where neurogenesis occurs throughout adulthood and in which the neuronal cell loss causes various demential states. The main goal of this study was to verify whether fetal neural progenitor cells (NPCs) from transgenic rats expressing green fluorescent protein (GFP) retain the ability to differentiate into neuronal cells and to integrate into the hippocampal circuitry after transplantation. Methods. NPCs were isolated from E14 (gestational age: 14 days postconception) transgenic-Lewis and wild-type Sprague-Dawley rat embryos. Wild-type and transgenic cells were expanded and induced to differentiate into a neuronal lineage in vitro. Immunocytochemical and electrophysiological analysis were performed in both groups. GFP-expressing cells were implanted into the hippocampus and recorded electrophysiologically 3 months thereafter. Immunohistochemical analysis confirmed neuronal differentiation, and the yield of neuronal cells was determined stereologically. Results. NPCs derived from wild-type and transgenic animals are similar regarding their ability to generate neuronal cells in vitro. Neuronal maturity was confirmed by immunocytochemistry and electrophysiology, with demonstration of voltage-gated ionic currents, firing activity, and spontaneous synaptic currents. GFP-NPCs were also able to differentiate into mature neurons after implantation into the hippocampus, where they formed functional synaptic contacts. Conclusions. GFP-transgenic cells represent an important tool in transplantation studies. Herein, we demonstrate their ability to generate functional neurons both in vitro and in vivo conditions. Neurons derived from fetal NPCs were able to integrate into the normal hippocampal circuitry. The high yield of mature neurons generated render these cells important candidates for restorative approaches based on cell therapy.

Personality traits in patients with juvenile myoclonic epilepsy

There is evidence of personality disorders in patients with juvenile myoclonic epilepsy (JME). To date, there have been no published quantitative studies on personality traits in JME. The aim of the work described here was to study a group of patients with JME and quantitatively measure personality traits. We evaluated 42 patients (mean age: 26.57 years, SD: 8.38) and 42 controls (mean age: 26.96, SD: 8.48) using a validated personality inventory, the Temperament and Character Inventory (TCI). We applied two scores, one for the Beck Depression Inventory and one for the State-Trait-Anxiety Inventory, as depression and anxiety may impact the performance of these patients on the TCI. We compared both groups on TCI scales using analysis of covariance with Beck Depression Inventory and State-Trait-Anxiety Inventory scores as covariates. Patients with JME obtained significantly higher scores on Novelty Seeking (P=0.001) and Harm Avoidance (P=0.002) and significantly lower scores on Self-Directedness (P=0.001). Patients with JME have a higher expression of impulsive personality traits that demand early recognition to avoid further consequences and facilitate social insertion, consequently avoiding future stigma. (C) 2011 Elsevier Inc. All rights reserved.

Inhibition of the renin-angiotensin system prevents seizures in a rat model of epilepsy

The RAS (renin angiotensin system) is classically involved in BP (blood pressure) regulation and water electrolyte balance, and in the central nervous system it has been mostly associated with homoeostatic processes, such as thirst, hormone secretion and thermoregulation. Epilepsies are chronic neurological disorders characterized by recurrent epileptic seizures that affect 1-3% of the world`s population, and the most commonly used anticonvulsants are described to be effective in approx. 70% of the population with this neurological alteration. Using a rat model of epilepsy, we found that components of the RAS, namely ACE (angiotensin-converting enzyme) and the AT(1) receptor (angiotensin II type I receptor) are up-regulated in the brain (2.6- and 8.2-fold respectively) following repetitive seizures. Subsequently, epileptic animals were treated with clinically used doses of enalapril, an ACE inhibitor, and losartan, an AT(1) receptor blocker, leading to a significant decrease in seizure severities. These results suggest that centrally acting drugs that target the RAS deserve further investigation as possible anticonvulsant agents and may represent an additional strategy in the management of epileptic patients.

Do psychiatric comorbidities predict postoperative seizure outcome in temporal lobe epilepsy surgery?

Clinical and demographic presurgical variables may be associated with unfavorable postsurgical neurological outcome in patients with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). However, few reports include preoperative psychiatric disorders as a factor predictive of long-term post-surgical MTLE-HS neurological Outcome. We used Engel`s criteria to follow 186 postsurgical patients with MTLE-HS for an average of 6 years. DSM-IV criteria and psychiatric comorbidity criteria specific to epilepsy (interictal dysphoric disorder, postictal and interictal psychosis) were used to assess presurgical psychiatric disorders. Kaplan-Meier event-free Survival and adjusted hazard ratios were estimated with unconditional logistic regression. Seventy-seven (41.4%) patients had a preoperative Axis I psychiatric diagnosis. Thirty-six patients had depression, I I interictal dysphoric disorder, 14 interictal psychosis, 6 postictal psychosis, and 10 anxiety disorders. Twenty-three (12.4%) patients had Axis 11 personality disorders. Regarding seizure outcome, preoperative anxiety disorders (P = 0.009) and personality disorders (P = 0.003) were positively Correlated with Engel class I B (remaining auras) or higher. These findings emphasize the importance of presurgical psychiatric evaluation, counseling, and Postsurgical follow-up of patients with epilepsy and psychiatric disorders. (C) 2009 Elsevier Inc. All rights reserved.

Central effects of Tityus serrulatus and Tityus bahiensis scorpion venoms after intraperitoneal injection in rats

A great number of studies on scorpion venoms associate their effects to the autonomic nervous system, and few data are available about their action on the central nervous system (CNS). The aim of this work was to evaluate some central effects after intraperitoneal injection of Tityus serrulatus or T. bahiensis scorpion venoms. The hippocampal concentration of some neurotransmitters and their metabolites were determined. Electroencephalographic and behavioral observations were performed, and all brains were removed for histopathological analysis of hippocampal areas. Both venoms induced electrographic and behavioral alterations despite T bahiensis venom affects less the electrographic activity than T. serrulatus venom. Neurochemical analysis demonstrated no alteration in the extracellular levels of almost all the neurotransmitters evaluated, at least in the hippocampus, and no neuronal loss in this area was observed. Meanwhile, extracellular concentration of HVA increased up to 10 times in approximately 1/3 of the animals of both groups. Scorpion venoms seem to exert a small but important central effect. More studies in this field are necessary because they may be useful in developing new strategies to reduce the damage caused by scorpion stings. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Temporal lobe epilepsy and social behavior: An animal model

Social behavior depends on the integrity of social brain circuitry. The temporal lobe is an important part of the social brain, and manifests morphological and functional alterations in autism spectrum disorders (ASD). Rats with temporal lobe epilepsy (TLE), induced with pilocarpine, were subjected to a social discrimination test that has been used to investigate potential animal models of ASD, and the results were compared with those for the control group. Rats with TLE exhibited fewer social behaviors than controls. No differences were observed in nonsocial behavior between groups. The results suggest an important role for the temporal lobe in regulating social behaviors. This animal model might be used to explore some questions about ASD pathophysiology. (c) 2008 Elsevier Inc. All rights reserved.

The non-coding RNA BC1 is down-regulated in the hippocampus of Wistar Audiogenic Rat (WAR) strain after audiogenic kindling

The aim of this study was to identify molecular pathways involved in audiogenic seizures in the epilepsy-prone Wistar Audiogenic Rat (WAR). For this, we used a suppression-subtractive hybridization (SSH) library from the hippocampus of WARs coupled to microarray comparative gene expression analysis, followed by Northern blot validation of individual genes. We discovered that the levels of the non-protein coding (npc) RNA BC1 were significantly reduced in the hippocampus of WARs submitted to repeated audiogenic seizures (audiogenic kindling) when compared to Wistar resistant rats and to both naive WARs and Wistars. By quantitative in situ hybridization, we verified lower levels of BC1 RNA in the GD-hilus and significant signal ratio reduction in the stratum radiatum and stratum pyramidale of hippocampal CA3 subfield of audiogenic kindled animals. Functional results recently obtained in a BC1-/- mouse model and our current data are supportive of a potential disruption in signaling pathways, upstream of BC1, associated with the seizure susceptibility of WARs. (C) 2010 Elsevier B.V. All rights reserved.

Increased Expression of GluR2-flip in the Hippocampus of the Wistar Audiogenic Rat Strain After Acute and Kindled Seizures

The Wistar Audiogenic Rat (WAR) is an epileptic-prone strain developed by genetic selection from a Wistar progenitor based on the pattern of behavioral response to sound stimulation. Chronic acoustic stimulation protocols of WARs (audiogenic kindling) generate limbic epileptogenesis, confirmed by ictal semiology, amygdale, and hippocampal EEG, accompanied by hippocampal and amygdala cell loss, as well as neurogenesis in the dentate gyrus (DG). In an effort to identify genes involved in molecular mechanisms underlying epileptic process, we used suppression-subtractive hybridization to construct normalized cDNA library enriched for transcripts expressed in the hippocampus of WARs. The most represented gene among the 133 clones sequenced was the ionotropic glutamate receptor subunit II (GluR2), a member of the a-amino-3-hydroxy-5-methyl-4-isoxazoleopropionic acid (AMPA) receptor. Although semiquantitative RT-PCR analysis shows that the hippocampal levels of the GluR2 subunits do not differ between naive WARs and their Wistar counterparts, we observed that the expression of the transcript encoding the splice-variant GluR2-flip is increased in the hippocampus of WARs submitted to both acute and kindled audiogenic seizures. Moreover, using in situ hybridization, we verified upregulation of GluR2-flip mainly in the CA1 region, among the hippocampal subfields of audiogenic kindled WARs. Our findings on differential upregulation of GluR2-flip isoform in the hippocampus of WARs displaying audiogenic seizures is original and agree with and extend previous immunohistochemical for GluR2 data obtained in the Chinese P77PMC audiogenic rat strain, reinforcing the association of limbic AMPA alterations with epileptic seizures. (C) 2009 Wiley-Liss, Inc.