Impact of hippocampal subfield histopathology in episodic memory impairment in mesial temporal lobe epilepsy and hippocampal sclerosis.

OBJECTIVE: The objective of the study was to analyze preoperative visual and verbal episodic memories in a homogeneous series of patients with mesial temporal lobe epilepsy (MTLE) and unilateral hippocampal sclerosis (HS) submitted to corticoamygdalohippocampectomy and its association with neuronal cell density of each hippocampal subfield. METHODS: The hippocampi of 72 right-handed patients were collected and prepared for histopathological examination. Hippocampal sclerosis patterns were determined, and neuronal cell density was calculated. Preoperatively, two verbal and two visual memory tests (immediate and delayed recalls) were applied, and patients were divided into two groups, left and right MTLE (36/36). RESULTS: There were no statistical differences between groups regarding demographic and clinical data. Cornu Ammonis 4 (CA4) neuronal density was significantly lower in the right hippocampus compared with the left (p=0.048). The groups with HS presented different memory performance - the right HS were worse in visual memory test [Complex Rey Figure, immediate (p=0.001) and delayed (p=0.009)], but better in one verbal task [RAVLT delayed (p=0.005)]. Multiple regression analysis suggested that the verbal memory performance of the group with left HS was explained by CA1 neuronal density since both tasks were significantly influenced by CA1 [Logical Memory immediate recall (p=0.050) and Logical Memory and RAVLT delayed recalls (p=0.004 and p=0.001, respectively)]. For patients with right HS, both CA1 subfield integrity (p=0.006) and epilepsy duration (p=0.012) explained Complex Rey Figure immediate recall performance. Ultimately, epilepsy duration also explained the performance in the Complex Rey Figure delayed recall (p<0.001). SIGNIFICANCE: Cornu Ammonis 1 (CA1) hippocampal subfield was related to immediate and delayed recalls of verbal memory tests in left HS, while CA1 and epilepsy duration were associated with visual memory performance in patients with right HS.

Differential effects of exercise on brain opioid receptor binding and activation in rats.

Physical exercise stimulates the release of endogenous opioid peptides supposed to be responsible for changes in mood, anxiety, and performance. Exercise alters sensitivity to these effects that modify the efficacy at the opioid receptor. Although there is evidence that relates exercise to neuropeptide expression in the brain, the effects of exercise on opioid receptor binding and signal transduction mechanisms downstream of these receptors have not been explored. Here, we characterized the binding and G protein activation of mu opioid receptor, kappa opioid receptor or delta opioid receptor in several brain regions following acute (7 days) and chronic (30 days) exercise. As regards short- (acute) or long-term effects (chronic) of exercise, overall, higher opioid receptor binding was observed in acute-exercise animals and the opposite was found in the chronic-exercise animals. The binding of [(35) S]GTPγS under basal conditions (absence of agonists) was elevated in sensorimotor cortex and hippocampus, an effect more evident after chronic exercise. Divergence of findings was observed for mu opioid receptor, kappa opioid receptor, and delta opioid receptor receptor activation in our study. Our results support existing evidence of opioid receptor binding and G protein activation occurring differentially in brain regions in response to diverse exercise stimuli. We characterized the binding and G protein activation of mu, kappa, and delta opioid receptors in several brain regions following acute (7 days) and chronic (30 days) exercise. Higher opioid receptor binding was observed in the acute exercise animal group and opposite findings in the chronic exercise group. Higher G protein activation under basal conditions was noted in rats submitted to chronic exercise, as visible in the depicted pseudo-color autoradiograms.

Parvalbumin expression and distribution in the hippocampal formation of Cebus apella.

New World primates play an important role in biomedical research. However, the literature still lacks information on many structural features of the brain in these species, particularly structures of the hippocampal formation that are related to long-term memory storage. This study was designed to provide information, for the first time, about the distribution and number of neurons expressing parvalbumin-immunoreactivity (PV-I) in the subregions of the hippocampal formation in Cebus apella, a New World primate species commonly used in biomedical research. Our results revealed that for several morphometric variables, PV-I cells differ significantly among the subregions CA1, CA2, CA3, and the hilus. Based upon our findings and those of other studies, we hypothesize that the proportional increase from monkeys to humans in PV-I cell density within CA1 is a factor contributing to the evolution of increased memory formation and storage.

Expression and activity of thimet oligopeptidase (TOP) are modified in the hippocampus of subjects with temporal lobe epilepsy (TLE).

OBJECTIVE: Thimet oligopeptidase (TOP) is a metalloprotease that has been associated with peptide processing in several nervous system structures, and its substrates include several peptides such as bradykinin, amyloid beta (Aß), and major histocompatibility complex (MHC) class I molecules. As shown previously by our research group, patients with temporal lobe epilepsy (TLE) have a high level of kinin receptors as well as kallikrein, a kinin-releasing enzyme, in the hippocampus. METHODS: In this study, we evaluated the expression, distribution, and activity of TOP in the hippocampus of patients with TLE and autopsy-control tissues, through reverse-transcription polymerase chain reaction (RT-PCR), enzymatic activity, Western blot, and immunohistochemistry. In addition, hippocampi of rats were analyzed using the pilocarpine-induced epilepsy model. Animals were grouped according to the epilepsy phases defined in the model as acute, silent, and chronic. RESULTS: Increased TOP mRNA expression, decreased protein levels and enzymatic activity were observed in tissues of patients, compared to control samples. In addition, decreased TOP distribution was also visualized by immunohistochemistry. Similar results were observed in tissues of rats during the acute phase of epilepsy model. However, increased TOP mRNA expression and no changes in immunoreactivity were found in the silent phase, whereas increased TOP mRNA expression and increased enzymatic activity were observed in the chronic phase. SIGNIFICANCE: The results show that these alterations could be related to a failure in the mechanisms involved in clearance of inflammatory peptides in the hippocampus, suggesting an accumulation of potentially harmful substances in nervous tissue such as Aß, bradykinin, and antigenic peptides. These accumulations could be related to hippocampal inflammation observed in TLE subjects.

Exercise-induced hippocampal anti-inflammatory response in aged rats.

Aging is often accompanied by cognitive decline, memory impairment and an increased susceptibility to neurodegenerative disorders. Most of these age-related alterations have been associated with deleterious processes such as changes in the expression of inflammatory cytokines. Indeed, higher levels of pro-inflammatory cytokines and lower levels of anti-inflammatory cytokines are found in the aged brain. This perturbation in pro- and anti-inflammatory balance can represent one of the mechanisms that contribute to age-associated neuronal dysfunction and brain vulnerability. We conducted an experimental study to investigate whether an aerobic exercise program could promote changes in inflammatory response in the brains of aged rats. To do so, we evaluated the levels of tumor necrosis factor alpha (TNFα), interleukin 1 beta (IL1ß), interleukin 6 (IL6) and interleukin 10 (IL10) in the hippocampal formation of 18 month old rats that underwent treadmill training over 10 consecutive days. Quantitative immunoassay analyses showed that the physical exercise increased anti-inflammatory cytokine levels IL10 in the hippocampal formation of aged rats, when compared to the control group. The hippocampal levels of pro-inflammatory cytokines IL1ß, IL6 and TNFα were not statistically different between the groups. However, a significant reduction in IL1ß/IL10, IL6/IL10 and TNFα/IL10 ratio was observed in the exercised group in relation to the control group. These findings indicate a favorable effect of physical exercise in the balance between hippocampal pro- and anti-inflammatory during aging, as well as reinforce the potential therapeutic of exercise in reducing the risk of neuroinflammation-linked disorders.

Effect of co-transporter blockers on non-synaptic epileptiform activity-computational simulation.

The important role of cation-chloride co-transporters in epilepsy is being supported by an increasing number of investigations. However, enormous complexity is involved since the action of these co-transporters has effects on the ionic homeostasis influencing directly the neuronal excitability and the tissue propensity to sustain seizure. To unravel the complex mechanisms involving the co-transporters action during seizure, this paper shows simulations of non-synaptic epileptiform activity and the effect of the blockage of the two different types of cation-chloride co-transporters present in the brain: Na, K and 2Cl co-transporter (NKCC) and K and Cl co-transporter (KCC). The simulations were performed with an electrochemical model representing the non-synaptic structure of the granule cell layer of the dentate gyrus (DG) of the rat hippocampus. The simulations suggest: (i) the potassium clearance is based on the systemic interplay between the Na/K pump and the NKCC co-transporters; (ii) the simultaneous blockage of the NKCC of the neurons and KCC of glial cells acts efficiently suppressing the epileptiform activities; and (iii) the simulations show that depending on the combined blockage of the co-transporters, the epileptiform activities may be suppressed or enhanced.

Experimental and clinical findings from physical exercise as complementary therapy for epilepsy.

Complementary therapies for preventing or treating epilepsy have been extensively used. This review focuses on the positive effects of physical exercise programs observed in clinical studies and experimental models of epilepsy and their significance as a complementary therapy for epilepsy. Information about the antiepileptogenic and neuroprotective effects of exercise is highlighted. Considering that exercise can exert beneficial actions such as reduction of seizure susceptibility, reduction of anxiety and depression, and consequently, improvement of quality of life of individuals with epilepsy, exercise can be a potential candidate as non-pharmacological treatment of epilepsy.

Activation and involvement of the lateral-posterior nucleus of the thalamus after a single generalized tonic-clonic seizure.

The lateral-posterior thalamic nuclei (LP) have been shown to play an important role in controlling epileptic activity. In addition, thalamic atrophy and neuronal loss have been observed in epilepsy. The objective of this study was to investigate whether lateral-posterior neuronal activation may be observed shortly after a single generalized seizure in rats submitted to the pilocarpine model of epilepsy. The results showed an increased lateral-posterior activation as soon as the seizure occurred, suggesting that neuronal loss in the thalamus is not only the consequence of chronic epilepsy.

Granule cell dispersion is not a predictor of surgical outcome in temporal lobe epilepsy with mesial temporal sclerosis.

The aim of this retrospective study of a series of patients with mesial temporal lobe epilepsy (MTLE) and mesial temporal sclerosis (MTS) was to analyze the association of granule cell dispersion (GCD) with surgical prognosis, patterns of MTS and clinical data. Hippocampal specimens from 66 patients with MTLE and unilateral MTS and from 13 controls were studied. Quantitative neuropathological evaluation was performed on NeuN-stained hippocampal sections. Patients' clinical data, types of MTS and surgical outcome were reviewed. GCD occurred in 45.5% of cases and was not correlated with clinical variable. More severe neuronal loss was observed in patients with GCD. Except for MTS Type 2 - observed only in four no- GCD patients - groups did not differ with respect to the types of MTS. Surgical outcome was similar in both groups. In conclusion, GCD was associated with the degree of hippocampal cell loss, but was not a predictor of surgical outcome.

Reduction of vascular reactivity in rat aortas following pilocarpine-induced status epilepticus.

OBJECTIVE: The authors investigated changes in vascular reactivity in rats following pilocarpine-induced status epilepticus. METHOD: Male Wistar rats weighing between 250g and 300g were used. Status epilepticus was induced using 385 mg/kg i.p. pilocarpine. After 40 days the thoracic aorta was dissected and divided into 4 mm rings and the vascular smooth muscle reactivity to phenylephrine was evaluated. RESULTS: Epilepsy decreased the contractile responses of the aortic rings to phenylephrine (0.1 nM-300 mM). To investigate if this reduction was induced by increasing NO production with/or hydrogen peroxide L-NAME and Catalase were used. L-NAME (N-nitro-L arginine methyl ester) increased vascular reactivity but the contractile response to phenylephrine increased in the epileptic group. Catalase administration decreased the contractile responses only in the rings of rats with epilepsy. CONCLUSIONS: Our findings demonstrated for the first time that epilepsy is capable of causing a reduction of vascular reactivity in rat aortas. These results suggest that vascular reactivity reduction is associated with increased production of Nitric Oxide (NO) as an organic attempt to avoid hypertension produced by excessive sympathetic activation.

Early exercise promotes positive hippocampal plasticity and improves spatial memory in the adult life of rats.

There is a great deal of evidence showing the capacity of physical exercise to enhance cognitive function, reduce anxiety and depression, and protect the brain against neurodegenerative disorders. Although the effects of exercise are well documented in the mature brain, the influence of exercise in the developing brain has been poorly explored. Therefore, we investigated the morphological and functional hippocampal changes in adult rats submitted to daily treadmill exercise during the adolescent period. Male Wistar rats aged 21 postnatal days old (P21) were divided into two groups: exercise and control. Animals in the exercise group were submitted to daily exercise on the treadmill between P21 and P60. Running time and speed gradually increased over this period, reaching a maximum of 18 m/min for 60 min. After the aerobic exercise program (P60), histological and behavioral (water maze) analyses were performed. The results show that early-life exercise increased mossy fibers density and hippocampal expression of brain-derived neurotrophic factor and its receptor tropomyosin-related kinase B, improved spatial learning and memory, and enhanced capacity to evoke spatial memories in later stages (when measured at P96). It is important to point out that while physical exercise induces hippocampal plasticity, degenerative effects could appear in undue conditions of physical or psychological stress. In this regard, we also showed that the exercise protocol used here did not induce inflammatory response and degenerating neurons in the hippocampal formation of developing rats. Our findings demonstrate that physical exercise during postnatal development results in positive changes for the hippocampal formation, both in structure and function.

A strength exercise program in rats with epilepsy is protective against seizures.

The beneficial effects of physical exercise on epilepsy, such as a decreased seizure frequency, have been observed following aerobic exercise programs in both clinical and experimental studies. However, it is not well clarified whether other types of exercise, including strength exercise, can provide similar benefits for epilepsy. Forty four animals with epilepsy were continuously monitored 24 h a day for 60 days and divided into two periods of 30 days. The first period was used to determine the number of seizures before beginning the physical exercise program, and the second period was utilized to determine the number of seizures during the strength training. The mean frequency of seizures in the control and SHAM groups increased significantly from period 1 to period 2. Although the frequency of seizures did not change significantly between the two periods of 30 days of observation in the strength exercise group, a significant reduction in the seizure frequency was observed compared with the control and SHAM groups in period 2. Our study demonstrated that a strength exercise program exerted a significant influence on the seizure frequency in animals with epilepsy and strengthens the observed beneficial effect of exercise on epilepsy that has been demonstrated in animal studies. The finding of this nonclinical study can open a new window to verify the beneficial contribution of strength exercise in epilepsy. Further experimental and clinical investigations are necessary to explore the extent to which strength exercise interferes with the epileptic condition.

Embodiment of a virtual prosthesis through training using an EMG-based human-machine interface: Case series.

Therapeutic strategies capable of inducing and enhancing prosthesis embodiment are a key point for better adaptation to and acceptance of prosthetic limbs. In this study, we developed a training protocol using an EMG-based human-machine interface (HMI) that was applied in the preprosthetic rehabilitation phase of people with amputation. This is a case series with the objective of evaluating the induction and enhancement of the embodiment of a virtual prosthesis. Six men and a woman with unilateral transfemoral traumatic amputation without previous use of prostheses participated in the study. Participants performed a training protocol with the EMG-based HMI, composed of six sessions held twice a week, each lasting 30 mins. This system consisted of myoelectric control of the movements of a virtual prosthesis immersed in a 3D virtual environment. Additionally, vibrotactile stimuli were provided on the participant's back corresponding to the movements performed. Embodiment was investigated from the following set of measurements: skin conductance response (affective measurement), crossmodal congruency effect (spatial perception measurement), ability to control the virtual prosthesis (motor measurement), and reports before and after the training. The increase in the skin conductance response in conditions where the virtual prosthesis was threatened, recalibration of the peripersonal space perception identified by the crossmodal congruency effect, ability to control the virtual prosthesis, and participant reports consistently showed the induction and enhancement of virtual prosthesis embodiment. Therefore, this protocol using EMG-based HMI was shown to be a viable option to achieve and enhance the embodiment of a virtual prosthetic limb.

Lovastatin decreases the synthesis of inflammatory mediators in the hippocampus and blocks the hyperthermia of rats submitted to long-lasting status epilepticus.

Statins may act on inflammatory responses, decreasing oxidative stress and also reducing temperature after a brain ischemic insult. Previous data have indicated that statins protect neurons from death during long-lasting status epilepticus (SE) and attenuate seizure behaviors in animals treated with kainic acid. In this context, the study described here aimed to investigate the effect of lovastatin on body temperature and on mRNA expression levels of hippocampal cytokines such as interleukin-1ß, interleukin-6, tumor necrosis factor α, and kinin B1 and B2 receptors of rats submitted to pilocarpine-induced SE. Quantitative real-time polymerase chain reaction showed a significant decrease in mRNA expression of interleukin-1ß, interleukin-6, tumor necrosis factor α, and kinin B1 receptor in animals with SE treated with lovastatin, compared with untreated animals with SE (P<0.001). Lovastatin also reduced SE-induced hyperthermia, indicating that mechanisms related to brain protection are triggered by this drug under conditions associated with acute excitotoxicity or long-lasting SE.

Spontaneous periodic hypothermia and hyperhidrosis: a possibly novel cerebral neurotransmitter disorder.

Spontaneous periodic episodes of hypothermia still defy medical knowledge. In 1969, Shapiro et al. described the first two cases of spontaneous periodic hypothermia associated with agenesis of the corpus callosum. Recently, Dundar et al. reported a case of spontaneous periodic hypothermia and hyperhidrosis without corpus callosum agenesis, suggesting that the periodic episodes of hypothermia might be of epileptiform origin. Here we describe two paediatric patients with spontaneous periodic hypothermia without corpus callosum agenesis and demonstrate, to our knowledge for the first time, altered levels of neurotransmitter metabolites within the cerebrospinal fluid.

Hippocampal plasticity in rats submitted to a gastric restrictive procedure.

Bariatric surgery has been the most effective therapeutic intervention for morbidly obese patients. However, recent evidence has shown that this procedure may cause serious neurological complications such as Wernicke encephalopathy, depression, and memory impairment. With this in mind, we conducted an experimental study to investigate whether weight-reduction surgery would promote morphological changes in the hippocampal formation, a brain region linked to cognitive and emotional processes. To do so, the present study evaluated the hippocampal expression of parvalbumin interneurons in rats submitted to a gastric restrictive procedure (experimental phytobezoar). Our results demonstrated that rats with gastric-reduced capacity presented a significant increase in the expression of the parvalbumin interneurons in the hippocampal CA1 and CA3 subfields. These data are the first experimental evidence that restrictive bariatric surgery may alter hippocampal cytoarchitecture.

Granule cell dispersion is associated with hippocampal neuronal cell loss, initial precipitating injury, and other clinical features in mesial temporal lobe epilepsy and hippocampal sclerosis.

PURPOSE: To characterize a 10-year series of patients with mesial temporal lobe epilepsy (MTLE) and unilateral hippocampal sclerosis (HS) and determine the histopathological characteristic of the association between granule cell dispersion (GCD) and hippocampal neuronal loss. METHODS: The study included 108 MTLE/HS patients. Histopathological analyses were performed in NeuN-stained hippocampal sections for HS pattern, neuronal density, dentate gyrus (DG) pathology, and granule cell layer width. Statistical tests investigated the association between DG pathologies and HS patterns, as well as the correlation of DG width with total hippocampal and subfield-specific neuronal densities. RESULTS: Fifty-six patients (51.9%) presented right HS. All the four ILAE HS patterns were represented (90 Type 1, 11 Type 2, 2 Type 3, and 5 no-HS). Sixty-seven patients (62.0%) presented GCD, 39 (36.1%) normal DG, and 2 (1.9%) narrow DG. GCD was associated with initial precipitating injury, higher numbers of monthly focal seizures and lifetime bilateral tonic-clonic seizures, longer epilepsy duration, and older age at surgery. GCD was prevalent in all HS patterns, except for Type 2 (81.8% normal versus 18.2% GCD, p = 0.005). GCD was associated with total hippocampal and subfield-specific neuronal loss, except for CA1. DG width correlated with total hippocampal (r = -0.201, p = 0.037) and CA4 neuronal densities (r = -0.299, p = 0.002). Patients with HS Type 1 had better surgical outcomes, with 51 (61.4%) seizure-free in the first year post-surgery. CONCLUSIONS: This study confirmed that seizure control in MTLE/HS patients submitted to surgical treatment is comparable worldwide. Moreover, histopathological analyses showed an association between GCD and hippocampal neuronal loss, especially in the CA4 subfield.

Do Hippocampal Neurons Really Count for Comorbid Depression in Patients With Mesial Temporal Lobe Epilepsy and Hippocampal Sclerosis? A Histopathological Study.

Depression is the most frequent psychiatric comorbidity seen in mesial temporal lobe epilepsy (MTLE) patients with hippocampal sclerosis (HS). Moreover, the HS is the most frequent pathological hallmark in MTLE-HS. Although there is a well-documented hippocampal volumetric reduction in imaging studies of patients with major depressive disorder, in epilepsy with comorbid depression, the true role of the hippocampus is not entirely understood. This study aimed to verify if patients with unilateral MTLE-HS and the co-occurrence of depression have differences in neuronal density of the hippocampal sectors CA1-CA4. For this purpose, we used a histopathological approach. This was a pioneering study with patients having both clinical disorders. However, we found no difference in hippocampal neuronal density when depression co-occurs in patients with epilepsy. In this series, CA1 had the lowest counting in both groups, and HS ILAE Type 1 was the most prevalent. More studies using histological assessments are needed to clarify the physiopathology of depression in MTLE-HS.

Favorable effects of physical activity for recovery in temporal lobe epilepsy.

Strategies that are efficacious for preventing or treating of epilepsy have been extensively used. This review discusses the positive effects of physical exercise program in experimental models of epilepsy, and considerations of the potential application of physical exercise strategy for preventing or treating temporal lobe epilepsy (TLE) are highlighted. Findings from animal studies indicate that exercise can modulate neuronal vulnerability to epileptic insults. Exercise treatment before a precipitating brain insult demonstrates a reduced brain susceptibility in the kindling or the pilocarpine model of epilepsy. In view of the beneficial effect of exercise during the epileptogenesis process, studies analyzed the influence of exercise after the development of chronic epilepsy. Behavioral analysis showed a reduced frequency of seizures during physical exercise program. Metabolic, electrophysiologic, and immunohistochemical studies have confirmed the positive influence of exercise on epilepsy. Taken into account that exercise can exert beneficial actions such as reduction of seizure susceptibility as observed in animal studies, and improvement of quality of life and reduction of anxiety and depression of individuals with epilepsy, physical exercise can be a potential candidate to be integrated with conventional therapy for epilepsy.

Social play impairment following status epilepticus during early development.

Neonatal status epilepticus (SE) disrupts prefrontal cortex and thalamus, brain regions related to social play. Juvenile play was evaluated using the "intruder-resident" paradigm following SE in 9-day-old Wistar pups of both genders. Quite interestingly, we demonstrated for the first time that neonatal SE produces social impairment in male rats, reduces locomotor activity in both genders and enhances self-grooming in female. Additional studies are necessary to clarify if these effects can impair social behavior across the life span.