Christian Frisch

Long-term cognitive impairment, neuronal loss and reduced cortical cholinergic innervation after recovery from sepsis in a rodent model

Sepsis is a disease with a high and growing prevalence worldwide. Most studies on sepsis up to date have been focused on reduction of short-term mortality. This study investigates cognitive and neuroanatomical long-term consequences of sepsis in a rat model. Sepsis was induced in male Wistar rats weighing 250-300 g by an i.p. injection of bacterial lipopolysaccharide (LPS, 10 mg/kg). Three months after complete recovery from sepsis, animals showed memory deficits in the radial maze and changes in open field exploratory patterns but unaffected inhibitory avoidance learning. Behavioral findings were matched by sepsis-induced loss of neurons in the hippocampus and the prefrontal cortex on serial sections after NeuN-staining and reduced cholinergic innervation in the parietal cortex measured by immunoradiography of vesicular acetylcholine transporter (VAChT). Together these results suggest that sepsis can induce persistent behavioral and neuroanatomical changes and warrant studies of the neurological long-term consequences of sepsis in humans.

Volumetric Magnetic Resonance Imaging of Functionally Relevant Structural Alterations in Chronic Epilepsy after Pilocarpine-induced Status Epilepticus in Rats

Summary:  Purpose: After pilocarpine‐induced epilepsy in rats, volumetric magnetic resonance imaging (MRI) reveals significant morphologic changes in functionally relevant structures of the brain. To relate structural changes to functional alteration, we studied the correlation of regional brain atrophy (e.g., of the hippocampus) with lesion‐induced learning deficits in the Morris water maze.

Neuropsychological course of voltage-gated potassium channel and glutamic acid decarboxylase antibody related limbic encephalitis

Autoantibodies (abs) to glutamic acid decarboxylase (GAD) and to voltage‐gated potassium channels (VGKC) induce distinct courses of limbic encephalitis, related to MRI findings, seizure outcome and cognition.

Amelioration of water maze performance deficits by topiramate applied during pilocarpine-induced status epilepticus is negatively dose-dependent

Temporal lobe epilepsy is characterized by a progressive loss of memory capacities, due to sclerosis and functional impairment of mesiotemporal brain areas. We have shown recently that topiramate (TPM) dose-dependently protects hippocampal CA1 and CA3 neurons during initial status epilepticus in the rat pilocarpine model of temporal lobe epilepsy by inhibition of mitochondrial transition pore opening. In the present study, in order to evaluate possible positive effects of the treatment on learning and memory, we investigated water maze performance of rats receiving different dosages of TPM (20 and 100 mg/kg) after 40 min and 4 mg/kg diazepam after 160 min of pilocarpine-induced status epilepticus in relation to performance of animals receiving 4 mg/kg diazepam after 40 min of SE, and to performance of sham-treated control animals. Unexpectedly, 20 but not 100 mg/kg TPM significantly extenuated short-term memory deficits. While neuroprotective effects of TPM were observed in hippocampal CA subfields of animals treated with 100 mg/kg TPM, cell loss in rats treated with 20 mg/kg TPM was indistinguishable from animals receiving diazepam only. The present results indicate a negative dose-dependency of memory-saving effects of TPM applied during status epilepticus apparently dissociated from hippocampal neuroprotection.

Dose‐dependent memory effects and cerebral volume changes after in utero exposure to valproate in the rat

Purpose:  Recent clinical studies raised concern of a cognitive teratogenicity of the major antiepileptic drug valproate. To investigate possible cerebral correlates, we established a forced self‐application schedule by diluting valproate in the drinking water of pregnant Wistar rats.

Treatment of immune-mediated temporal lobe epilepsy with GAD antibodies

PURPOSE Temporal lobe epilepsy with antibodies (abs) against the glutamic acid decarboxylase 65 isoform (GAD-TLE) is known as an immune-mediated neurological syndrome. Here we evaluate the therapy response to various immunotherapies and epilepsy surgery in this syndrome. METHOD All patients with GAD-TLE and follow-up data and stored serum and CSF samples, identified and treated at the Bonn centre from 2002 to 2010, were studied retrospectively. Seizure freedom for ≥1 year and reduction of ≥50%, i.e. therapy response, were assessed. GAD-ab titres and neuropsychological performances were documented prior and after individual interventions. RESULTS Thirteen patients with GAD-TLE were identified with the following seizure responses: corticosteroids (5 responders out of 11 treated patients); i.v. immunoglobulins (1/5), apheresis therapy (1/8); and natalizumab (1/1), selective amygdala-hippocampectomy (2/3). None of the patients achieved sustained seizure freedom apart from one patient. This patient was on antiepileptic drug treatment after discontinuation of immunotherapy. CONCLUSION The seizure response to immunotherapies in patients with GAD-TLE was poor. Corticosteroids were the most effective regarding seizure response. Especially the poor effects of apheresis therapies support the idea that GAD-abs are not directly pathogenic. None of three patients was seizure-free after temporal lobe surgery suggesting that GAD-TLE patients respond worse than others to this type of intervention. Our results reflect the chronic course of the disease with low likelihood for patients with GAD-TLE to attain long-term seizure freedom.

Positive correlation between the density of neuropeptide y positive neurons in the amygdala and parameters of self-reported anxiety and depression in mesiotemporal lobe epilepsy patients.

BACKGROUND Neuropeptide Y (NPY) has been implicated in depression, anxiety, and memory. Expression of human NPY and the number of NPY-positive neurons in the rodent amygdala correlate with anxiety and stress-related behavior. Increased NPY expression in the epileptic brain is supposed to represent an adaptive mechanism counteracting epilepsy-related hyperexcitability. We attempted to investigate whether NPY-positive neurons in the human amygdala are involved in these processes. METHODS In 34 adult epileptic patients undergoing temporal lobe surgery for seizure control, the density of NPY-positive neurons was assessed in the basal, lateral, and accessory-basal amygdala nuclei. Cell counts were related to self-reported depression, anxiety, quality of life, clinical parameters (onset and duration of epilepsy, seizure frequency), antiepileptic medication, and amygdala and hippocampal magnetic resonance imaging volumetric measures. RESULTS Densities of NPY-positive basolateral amygdala neurons showed significant positive correlations with depression and anxiety scores, and they were negatively correlated with lamotrigine dosage. In contrast, NPY cell counts showed no relation to clinical factors or amygdalar and hippocampal volumes. CONCLUSIONS The results point to a role of amygdalar NPY in negative emotion and might reflect state processes at least in patients with temporal lobe epilepsy. Correlations with common clinical parameters of epilepsy were not found. The question of a disease-related reduction of the density of NPY-positive amygdalar neurons in temporal lobe epilepsy requires further investigation.

Intrauterine valproate exposure is associated with alterations in hippocampal cell numbers and folate metabolism in a rat model of valproate teratogenicity

PURPOSE Valproate is one of the most commonly used anticonvulsive drugs. Despite its significant benefits, the teratogenicity of valproate is a relevant problem in the treatment of women of childbearing age. In addition to major congenital malformations, such as neural tube defects, reduced intelligence and attention after intrauterine valproate exposure are reported. Until now the mechanisms of teratogenicity of VPA are poorly understood and concepts how to reduce valproate teratogenicity are lacking. METHODS In a rat model of valproate teratogenicity we examined hippocampal cell structure in 4 week old animals with a stereological approach. As potential mechanisms of VPA teratogenicity we examined histone acetylation by western blotting and metabolites of the folate metabolism as well as global DNA methylation by tandem mass spectrometry in the brain and liver tissue of newborn pups (p0). RESULTS We found an increase in the number of neurons in the hippocampal areas CA1/2 (p=0.018) and CA3 (p=0.022), as well as a decreased number of astrocytes in CA1/2 (p=0.004) and CA3 (p=0.003) after intrauterine VPA exposure, as a possible indication of altered cell differentiation during intrauterine VPA exposure. Valproate exposure was also associated with an increase in 5-methyl-tetrahydrofolate (THF) (p=0.002) and a decrease in 5-10-methenyl-THF in the brain of newborn pups, as well as a reduced homocysteine plasma level (p<0.001). The described changes in hippocampal cell numbers and folate metabolism were only significant after high-dose intrauterine VPA exposure indicating a dose-dependent effect. VPA exposure was not associated with changes in histone acetylation or global DNA methylation in brain tissue in newborn pups. CONCLUSION This study shows that intrauterine VPA exposure is associated with changes in hippocampal cell numbers in the CA1/2 and CA3 region and in folate metabolism.

An efficient method for fractionated whole rodent brain radiation

Abstract Objective: In order to test for mechanisms of whole brain radio therapy side effects and possible neuroprotective measures, a rodent model is desirable. In many models, a high single dose of 8–20 Gray (Gy) of whole brain irradiation is used. These experimental radiation protocols do not closely reflect the clinical situation, where the cumulative dosage is applied in smaller fractions. We describe an efficient method to perform repetitive, fractionated whole brain radio therapy to the rat brain. Methods: Fifteen-week-old rats were irradiated with a dose of 5 or 10 Gy on four consecutive days, resulting in a cumulative dose in opposing fields of 20 Gy (n = 15) and 40 Gy (n = 17), respectively. Sham-irradiated rats (n = 14) received the same procedure but without application of cranial irradiation. Four collimators with a diameter of 3 cm each were used to place four rats and an ionization chamber simultaneously in the dose field for monitoring. Results: Fourteen days after the procedure, irradiated animals showed decreased open-field activity (two-tailed t-test, sham versus 20 Gy, P<0·001; sham versus 40 Gy, P = 0·002), but no cognitive deficit as indicated by latencies in the Morris water maze test. Six weeks after the irradiation, no group showed alterations of histopathology such as vascular changes, demyelination, or white matter necrosis. Discussion: The proposed model represents an efficient and safe method to perform fractioned high-dose irradiation of the rodent brain. Speculatively, it is possible to increase the cumulative dosage and dose per fraction used in this model to achieve a higher degree of radiation-induced toxicity.