The risk for behavioural deficits is determined by the maternal immune response to prenatal immune challenge in a neurodevelopmental model.

BACKGROUND: Schizophrenia is a highly disabling psychiatric disorder with a proposed neurodevelopmental basis. One mechanism through which genetic and environmental risk factors might act is by triggering persistent brain inflammation, as evidenced by long-lasting neuro-immunological disturbances in patients. Our goal was to investigate whether microglia activation is a neurobiological correlate to the altered behaviour in the maternal immune activation (MIA) model, a well-validated animal model with relevance to schizophrenia. A recent observation in the MIA model is the differential maternal body weight response to the immune stimulus, correlated with a different behavioural outcome in the offspring. Although it is generally assumed that the differences in maternal weight response reflect differences in cytokine response, this has not been investigated so far. Our aim was to investigate whether (i) the maternal weight response to MIA reflects differences in the maternal cytokine response, (ii) the differential behavioural phenotype of the offspring extends to depressive symptoms such as anhedonia and (iii) there are changes in chronic microglia activation dependent on the behavioural phenotype. METHODS: Based on a dose-response study, MIA was induced in pregnant rats by injecting 4mg/kg Poly I:C at gestational day 15. Serum samples were collected to assess the amount of TNF-α in the maternal blood following MIA. MIA offspring were divided into weight loss (WL; n=14) and weight gain (WG; n=10) groups, depending on the maternal body weight response to Poly I:C. Adult offspring were behaviourally phenotyped for prepulse inhibition, locomotor activity with and without amphetamine and MK-801 challenge, and sucrose preference. Finally, microglia activation was scored on CD11b- and Iba1-immunohistochemically stained sections. RESULTS: Pregnant dams that lost weight following MIA showed increased levels of TNF-α compared to controls, unlike dams that gained weight following MIA. Poly I:C WL offspring showed the most severe behavioural outcome. Poly I:C WG offspring, on the other hand, did not show clear behavioural deficits. Most interestingly a reduced sucrose preference indicative of anhedonia was found in Poly I:C WL but not Poly I:C WG offspring compared to controls. Finally, there were no significant differences in microglia activation scores between any of the investigated groups. CONCLUSIONS: The individual maternal immune response to MIA is an important determinant of the behavioural outcome in offspring, including negative symptoms such as anhedonia. We failed to find any significant difference in the level of microglia activation between Poly I:C WL, Poly I:C WG and control offspring.

Manganese-enhanced MRI reflects seizure outcome in a model for mesial temporal lobe epilepsy.

The neurobiological processes resulting in epilepsy, known as epileptogenesis, are incompletely understood. Manganese-enhanced MRI (MEMRI) can potentially aide in this quest as it provides superior tissue contrast, particularly of the hippocampal subregions. This longitudinal study aims to characterise the changes in the hippocampus of the post kainic acid-induced status epilepticus (KASE) rat model of mesial temporal lobe epilepsy using MEMRI in vivo. Serial acquisition of T(1)-weighted MEMRI images were taken before, 2 days and 6 weeks after KASE (10-30 mg/kg, i.p.) in 14 rats and in 11 control rats, while a second cohort of control (N=6) and epileptic animals (N=10) was imaged at 2 months post KASE only. MnCl(2) (50 mM, 10 µl) was administered in the right lateral ventricle 1 day before scanning. Regions of interest were drawn around the hippocampus and several subregions of the hippocampus (CA1, CA3 and dentate gyrus). Markers of epilepsy such as spontaneous recurrent seizures, hippocampal neuronal loss and mossy fiber sprouting were quantified. A persistent increase in MEMRI signal intensity was found in the hippocampus, CA1 and dentate gyrus in the KASE group compared to the control group (ANOVA P<0.05). The intensity signal in the hippocampus and subregions correlated inversely with the frequency of spontaneous recurrent seizures in the chronic epileptic phase, however there was no relationship observed between histopathological changes such as cell loss and mossy fiber sprouting with seizures. This study demonstrates that MEMRI is able to detect imaging changes in the hippocampus during the course of epileptogenesis relevant for seizure expression. These data strongly indicate a relationship between manganese enhancement and spontaneous seizure outcome, suggesting that MEMRI could provide a preclinical biomarker for the severity of epileptogenesis in vivo in animal models.

Changes in hippocampal GABAA/cBZR density during limbic epileptogenesis: relationship to cell loss and mossy fibre sprouting.

Reduced GABA(A)/central benzodiazepine receptor (GABA(A)/cBZR) density, mossy fibre sprouting (MFS) and hippocampal cell loss are well described pathological features of human temporal lobe epilepsy (TLE), and animal models thereof. However, the temporal relationship of their development, and their roles in the emergence of the epilepsy, are uncertain. This was investigated in the kainic acid (KA)-induced post-status epilepticus (SE) model of TLE. Male Wistar rats (7 weeks, n=53) were randomised into control and KA groups. At 24h, 2, 4 or 6 weeks sham and KA post-SE animals were euthanised, brains extracted and GABA(A)/cBZR density, neuronal loss and MFS measured in hippocampal sub-regions. GABA(A)/cBZR density (B(max)) was measured by saturation-binding analysis using [(3)H]-flumazenil. At 24h post-SE GABA(A)/cBZR density was increased in almost all hippocampal subregions, but was decreased at the later time points with the exception of the dentate gyrus. There was significant neuronal loss in the CA3 SPc region (-24 ± 9.3%, p<0.05) at 24h, which remained stable at the later time points associated with an elevated GABA(A)/cBZR density per surviving neuron at 24h post-SE (+56.4%; p<0.05) which returned to control levels by 6 weeks post-SE. MFS in the dentate gyrus progressively increased over the 6 weeks following SE (+70.6% at 6 weeks), at which time there was a significant inverse relationship with GABA(A)/cBZR binding (r(2)=0.87; p=0.02). The temporal evolution of GABA(A)/cBZR density changes post-KA-induced SE, and the relationship with decreases in hippocampal pyramidal cell numbers and MFS, may point to a key role for these changes in the pathogenesis of acquired limbic epileptogenesis.

Vagus nerve stimulation does not affect spatial memory in fast rats, but has both anti-convulsive and pro-convulsive effects on amygdala-kindled seizures.

Vagus nerve stimulation (VNS) is an adjunctive treatment for refractory epilepsy. Using a seizure-prone Fast-kindling rat strain with known comorbid behavioral features, we investigated the effects of VNS on spatial memory, epileptogenesis, kindled seizures and body weight. Electrodes were implanted in both amygdalae and around the left vagus nerve of 17 rats. Following recovery, rats were tested in the Morris water-maze utilizing a fixed platform paradigm. The VNS group received 2 h of stimulation prior to entering the Morris water-maze. Rats were then tested in the kindling paradigm wherein the VNS group received 2 h of stimulation prior to daily kindling stimulation. Finally, the abortive effects of acute VNS against kindling-induced seizures were determined in fully kindled rats by applying VNS immediately after the kindling pulse. Body weight, water consumption and food intake were measured throughout. Memory performance in the Morris water-maze was not different between control and vagus nerve stimulation rats. Similarly, kindling rate was unaffected by antecedent VNS. However, pro-convulsive effects (P<0.05) were noted, when VNS was administered prior to the kindling pulse in fully kindled rats. Yet, paradoxically, VNS showed anti-convulsant effects (P<0.01) in those rats when applied immediately after the kindling stimulus. Body weight was significantly lower throughout kindling (P<0.01) in VNS-treated rats compared with controls, which was associated with reduced food intake (P<0.05), but without difference in water consumption. VNS appears to be devoid of significant cognitive side effects in the Morris water-maze in Fast rats. Although VNS exhibited no prophylactic effect on epileptogenesis or seizure severity when applied prior to the kindling stimulus, it showed significant anti-convulsant effects in fully kindled rats when applied after seizure initiation. Lastly, VNS prevented the weight gain associated with kindling through reduced food intake.

The mechanism of action of vagus nerve stimulation for refractory epilepsy: the current status.

Vagus nerve stimulation (VNS) is a neurophysiologic treatment for patients with medically or surgically refractory epilepsy. Since the first human implant in 1989, more than 10,000 patients have been treated with VNS. The precise mechanism of action remains to be elucidated. Animal experiments with VNS were initially performed to demonstrate efficacy and safety preceding the clinical trials in human patients. Mechanism of action research involving animal experiments can provide essential clues. Animal experiments are often labor-intensive even in the hands of experienced researchers, however, and the results remain only a reflection of the complicated pathophysiologic systems of the human brain. Mechanism of action research in human patients treated with VNS is particularly challenging because of safety concerns, the large number of patients required, and the heterogeneous nature of various small patient series. This study provides an overview of the progress that has been made in the past 10 years through neurophysiologic, neuroanatomic, neurochemical, and cerebral blood flow studies in animals and patients treated with VNS. Further elucidation of the mechanism of action of VNS may increase its clinical efficacy. It may also provide inspiration for the development of new therapeutic modalities for refractory epilepsy.

Detection of spike and wave discharges in the cortical EEG of genetic absence epilepsy rats from Strasbourg.

Genetic absence epilepsy rats from Strasbourg (GAERS) are a strain of Wistar rats in which all animals present spontaneous occurrence of spike and wave discharges (SWD) in the cortical electroencephalogram (EEG). In this paper, we present a method for the detection of SWD, based on the key observation that SWD are quasi-periodic signals. A spectral-comb based analysis method is used to extract the fundamental frequency and the percentage of energy explained by the harmonic spectral components is subsequently used as a detection parameter. It is shown that a maximum sensitivity and specificity of up to 96 per cent can be achieved. We also compared the performance of this method with the methods presented in the literature and conclude that the surplus value of the novel detection method lies in the higher specificity that can be obtained in the analysis of long-term EEG fragments, which are contaminated by artefacts and contain large portions of slow-wave sleep.

Anti-epileptogenesis research: the clinical relevance.

In recent years, different research lines have examined the epileptogenic process in order to understand the different stages in this process, and with the hope that early recognition and intervention could prevent chronic epilepsy in patients with epileptic seizures. In animals, acquired epilepsy is studied most commonly with kindling models, status epilepticus models and traumatic brain injury models. Molecular genetic studies substantially help to understand age-specific channel and receptor abnormalities. Major progress has been made in recent years and we are now waiting for the first large scale multi-center clinical trials that test the possible anti-epileptogenic properties of anti-epileptic drugs or other compounds in well defined patient groups. In clinical practice, a structured diagnostic work-up in all patients with recurrent seizures is a first and necessary step in the recognition of patients at risk for developing chronic and refractory epilepsy.

Imaging brain inflammation in epilepsy.

Epilepsy is a highly common chronic neurological disorder. Although symptomatic treatment is available, 30-40% of epilepsy patients still remain resistant to anti-epileptic drugs. The primary identification and extensive characterization of the pathological substrates underlying epilepsy would facilitate the development of novel treatments, including disease-modifying and anti-epileptogenic therapies. A plethora of evidence points toward an undeniable role of brain inflammation in epileptogenesis. However, the exact role of this process remains unfortunately not clear. Non-invasive imaging of brain inflammation can promote our fundamental knowledge, which may lead to better insights into the role of brain inflammation in disease ontogenesis. Moreover, it will allow us to investigate whether the visualization of this process can serve as a validated biomarker for epilepsy. In turn, such can lead to major perspectives regarding the development and evaluation of anti-inflammatory treatments, and screening possibilities for patients at risk. Here, we first discuss the applications for imaging of the different brain inflammation constituents. Secondly, we review the available approaches for molecular imaging of brain inflammation in general and finally present the current research on the imaging of brain inflammation in patients and experimental models of epilepsy. The current imaging toolbox is limited by the range of neuroinflammatory targets, which can be visualized at present, and in addition, the often indirect approaches used. We believe that research in this field will further advance as highly specific ligands, and producible and practical imaging approaches will become available.

Subchronic memantine induced concurrent functional disconnectivity and altered ultra-structural tissue integrity in the rodent brain: revealed by multimodal MRI.

BACKGROUND: An effective NMDA antagonist imaging model may find key utility in advancing schizophrenia drug discovery research. We investigated effects of subchronic treatment with the NMDA antagonist memantine by using behavioural observation and multimodal MRI. METHODS: Pharmacological MRI (phMRI) was used to map the neuroanatomical binding sites of memantine after acute and subchronic treatment. Resting state fMRI (rs-fMRI) and diffusion MRI were used to study the changes in functional connectivity (FC) and ultra-structural tissue integrity before and after subchronic memantine treatment. Further corroborating behavioural evidences were documented. RESULTS: Dose-dependent phMRI activation was observed in the prelimbic cortex following acute doses of memantine. Subchronic treatment revealed significant effects in the hippocampus, cingulate, prelimbic and retrosplenial cortices. Decreases in FC amongst the hippocampal and frontal cortical structures (prelimbic, cingulate) were apparent through rs-fMRI investigation, indicating a loss of connectivity. Diffusion kurtosis MRI showed decreases in fractional anisotropy and mean diffusivity changes, suggesting ultra-structural changes in the hippocampus and cingulate cortex. Limited behavioural assessment suggested that memantine induced behavioural effects comparable to other NMDA antagonists as measured by locomotor hyperactivity and that the effects could be reversed by antipsychotic drugs. CONCLUSION: Our findings substantiate the hypothesis that repeated NMDA receptor blockade with nonspecific, noncompetitive NMDA antagonists may lead to functional and ultra-structural alterations, particularly in the hippocampus and cingulate cortex. These changes may underlie the behavioural effects. Furthermore, the present findings underscore the utility and the translational potential of multimodal MR imaging and acute/subchronic memantine model in the search for novel disease-modifying treatments for schizophrenia.

Fluctuating and constant valproate administration gives equivalent seizure control in rats with genetic and acquired epilepsy.

PURPOSE: Controlled-release formulations of Valproate (VPA) reduce side effects by minimizing peak plasma VPA concentrations in patients with epilepsy. However, the impact of this on anti-seizure efficacy has not been thoroughly explored. Here the pharmacokinetics and pharmacodynamics of chronic intermittent (consequently, peak VPA concentrations) and continuous VPA administration were directly compared in two rat models of epilepsy. METHODS: Genetic Absence Epilepsy Rats from Strasbourg (GAERS) received a single acute bolus of VPA (100 mg/kg intravenously) combined with electroencephalography (EEG) and/or blood sampling for 180 min post-injection. GAERS and epileptic rats post-kainic acid-induced status epilepticus were chronically infused intravenously (3-5 days, respectively) with (i) saline followed by in random order (ii) intermittent and (iii) continuous VPA (42 mg/kg/h), separated by two days of wash-out. Seizures were quantified using video-EEG monitoring and VPA levels measured in brain, cerebrospinal fluid and plasma. RESULTS: Following acute VPA administration seizure suppression in GAERS persisted after plasma VPA levels became very low. Chronic intermittent and continuous VPA significantly suppressed seizures in both models (p<0.01) with no difference between administration regimens. In GAERS, the pattern of seizure suppression during intermittent treatment was constant, in contrast to the fluctuating VPA plasma and brain levels. There was discordance between the temporal pattern of plasma, brain VPA levels and seizure suppression efficacy in GAERS. CONCLUSION: Administration regimes that result in fluctuating VPA blood levels achieve equivalent sustained seizure suppression as those that maintain steady mid-range concentrations.

Ectopic gastric mucosa presenting as a polypoid mass within a Meckel's diverticulum.

A 32-year-old man presented with severe abdominal pain located in the mesogastrium and right hemi-abdomen. A barium transit study showed a tubular structure of 6 cm arising from a bowel loop in the distal ileum, with an intraluminal polypoid mass near the bottom. Diagnosis of a benign lesion within a Meckel's diverticulum was made. Anatomopathology confirmed a Meckel's diverticulum and demonstrated that the polypoid mass was caused by an unusual great ectopic island of gastric mucosa.