Inhibition of nitric oxide synthase does not alter basal permeability of the blood-brain barrier

The goal of the present study was to determine the role of basal synthesis/release of nitric oxide on the basal permeability characteristics of the blood-brain barrier to various sized molecules in vivo. We examined the pial microcirculation in rats using intravital fluorescence microscopy. Permeability of the blood-brain barrier was quantitated by calculating the clearance of fluorescent-labeled albumin (mol.wt.=69,000 Da; FITC-albumin), fluorescent-labeled dextran (mol.wt.=10,000 Da; FITC-dextran-10K) or sodium fluorescein (mol.wt.=376; NaFl) in the absence and presence of an inhibitor of nitric oxide synthase (N(G)-monomethyl-L-arginine; L-NMMA; 10 and 100 microM). During superfusion with vehicle, clearance of FITC-albumin, FITC-dextran-10K and NaFl from pial vessels and diameter of pial arterioles remained constant. To determine whether basal synthesis/release of nitric oxide affected basal permeability of the blood-brain barrier, we examined the effects of L-NMMA (10 and 100 microM). In addition, we examined the adherence of leukocytes to cerebral venular endothelium using rhodamine 6G. Although topical application of L-NMMA produced constriction of pial arterioles, L-NMMA did not alter the permeability characteristics of the blood-brain barrier to FITC-albumin, FITC-dextran-10K or NaFl. Further, the adherence of leukocytes to the endothelium appeared to be similar while suffusing with vehicle and L-NMMA (100 microM). Thus, the findings of the present study suggest that while basal synthesis/release of nitric oxide may play an important role in regulation of basal tone of cerebral blood vessels, it does not appear that basal synthesis/release of nitric oxide plays an important role in maintaining the integrity of the blood-brain barrier to large or small molecules.     

Interleukin-2 does not cross the blood-brain barrier by a saturable transport system

Blood-borne interleukin-2 (IL-2), like other cytokines, is known to affect the central nervous system (CNS). One mechanism by which circulating substances can alter brain function is to directly cross the blood-brain barrier (BBB). We investigated the ability of IL-2 to cross the BBB, the interface between the periphery and the CNS. IL-2 labeled with ¹²⁵I (I-IL-2) was injected into mice intravenously and its rate of entry into the brain determined by multiple-time regression analysis. I-IL-2 was found to enter the brain about 10 times faster than albumin. Neither morphine nor antibodies to IL-2, IL-1α, or the IL-1 receptor affected the entry of I-IL-2. High performance liquid chromatography (HPLC) confirmed that the radioactivity entering the brain represented intact cytokine. However, excess unlabeled IL-2 was unable to impede the entry of I-IL-2, indicating that this transport is nonsaturable. This contrasts with saturable transport systems found for the cytokines IL-1α and TNF-α, but still may explain how IL-2 can exert central effects.     

Inhibition of nitric oxide synthase does not alter basal permeability of the blood–brain barrier

The goal of the present study was to determine the role of basal synthesis/release of nitric oxide on the basal permeability characteristics of the blood–brain barrier to various sized molecules in vivo. We examined the pial microcirculation in rats using intravital fluorescence microscopy. Permeability of the blood–brain barrier was quantitated by calculating the clearance of fluorescent-labeled albumin (mol.wt.=69,000 Da; FITC–albumin), fluorescent-labeled dextran (mol.wt.=10,000 Da; FITC–dextran-10K) or sodium fluorescein (mol.wt.=376; NaFl) in the absence and presence of an inhibitor of nitric oxide synthase (N^G-monomethyl- -arginine; -NMMA; 10 and 100 μM). During superfusion with vehicle, clearance of FITC–albumin, FITC–dextran-10K and NaFl from pial vessels and diameter of pial arterioles remained constant. To determine whether basal synthesis/release of nitric oxide affected basal permeability of the blood–brain barrier, we examined the effects of -NMMA (10 and 100 μM). In addition, we examined the adherence of leukocytes to cerebral venular endothelium using rhodamine 6G. Although topical application of -NMMA produced constriction of pial arterioles, -NMMA did not alter the permeability characteristics of the blood–brain barrier to FITC–albumin, FITC–dextran-10K or NaFl. Further, the adherence of leukocytes to the endothelium appeared to be similar while suffusing with vehicle and -NMMA (100 μM). Thus, the findings of the present study suggest that while basal synthesis/release of nitric oxide may play an important role in regulation of basal tone of cerebral blood vessels, it does not appear that basal synthesis/release of nitric oxide plays an important role in maintaining the integrity of the blood–brain barrier to large or small molecules.     

Naloxone does not alter amphetamine-induced rotational behavior or striatal dopamine levels of nigrally-lesioned rats

Previous studies on rats have shown that the opioid antagonist naloxone attenuates amphetamine-induced stimulation of locomotor activity and increases in extracellular dopamine in the brain. However, in this study, naloxone did not attenuate amphetamine-induced rotational behavior or increases of extracellular dopamine in the intact striatum of nigrally-lesioned rats. These results suggest differences in the way in which endogenous opioids contribute to the behavioral and neurochemical effects of amphetamine in nigrally-lesioned compared to intact rats     

Chronic valproate or levetiracetam treatment does not influence cytokine levels in humans

PurposeThere is growing evidence that complex interactions between seizures and the immune system shape the course of epilepsy. However, systematic analyses of the effects of antiepileptic drugs (AED) on the immune system in humans are rare. We performed a prospective study on the influence of the widely used AED valproate and levetiracetam on interictal immunological parameters.Methods36 patients were prospectively included. 15 were started on valproate (5 female (33%), age 54 ± 27 years, 12 (80%) on monotherapy), 21 on levetiracetam (10 female (48%), age 45 ± 19 years, 17 (81%) on monotherapy). Before treatment and after 3 months, we performed a differential blood count and analyzed the distribution of CD3⁺CD4⁺-, CD3⁺CD8⁺- and CD4⁺CD25⁺-leukocyte subsets using flow cytometry. In addition, we determined the concentrations of IL-1β, IL-6, TNF-α and MCP-1 in the peripheral blood using ELISAs.ResultsValproate intake resulted in a significant decrease of the total white blood count (6.96 ± 1.23/nl vs. 6.13 ± 1.57/nl, p = 0.026) and of absolute count and percentage of neutrophils (4.60 ± 1.05/nl vs. 3.69 ± 1.30/nl, p = 0.01; 65.4 ± 7.9% vs. 59.5 ± 11.5%, p = 0.01, respectively). The percentage of CD3⁺CD4⁺-lymphocytes dropped significantly (50.4 ± 10.9% vs. 45.3 ± 12.3%, p = 0.002). Levetiracetam treatment resulted in a decrease of the percentage of CD4⁺CD25⁺-lymphocytes (26.1 ± 8.0% vs. 21.5 ± 9.2%, p = 0.01) but did not significantly alter absolute counts. Neither valproate nor levetiracetam were associated with significant changes in cytokines.ConclusionValproate intake results in profound changes of white blood cell count and subset distribution. Cytokine levels were not influenced by valproate or levetiracetam.     

Recombinant human interferon-alpha does not alter reward behavior, or neuroimmune and neuroendocrine activation in rats

Recombinant human interferon-alpha (IFN-alpha) induces depression, and neuroendocrine and neuroimmune activation, in a significant number of patients undergoing treatment for viral illnesses (e.g., hepatitis C), yet these effects have not been consistently reproduced in rodents. As such, we sought to determine the effects of acute or chronic IFN-alpha treatment on basic reward and immobility in the forced swim test (FST), neuroendocrine and neuroimmune activation, and monoamine turnover in brain. In the first experiment, male Wistar rats (N = 7/group) treated with human recombinant IFN-alpha (100,000 IU/kg, i.p.), as compared to saline, did not exhibit alterations to rate of sucrose pellet self-administration or total reinforcers obtained, corticosterone release, plasma IL-6 release, IL-1beta or IL-6 mRNA expression in hippocampus, or monoamine turnover in prefrontal cortex, striatum, nucleus accumbens, or amygdala. However, acute IFN-alpha decreased body weight and produced a trend toward reduced food consumption in the home cage 2 h after injection. In the second experiment, Wistar rats (N=4/group) were subjected to a chronic treatment regimen of saline or IFN-alpha (100,000 IU/kg, i.p.) once daily for 14 consecutive days. The data reveal that animals exposed to chronic IFN-alpha exhibited similar amounts of time immobile and similar latencies to primary immobility in the FST as compared to saline-treated controls. Chronic IFN-alpha did not induce corticosterone release, plasma TNF-alpha, or IL-6 release. Tissue monoamine analysis revealed that chronic IFN-alpha reduced DA levels in prefrontal cortex, and decreased 5-HT levels and increased 5-HT turnover in amygdala. In the third experiment, Wistar rats (N = 4/group) were exposed to either acute or chronic pegylated IFN-alpha (pegIFN-alpha: 3.25, 10 or 75 mg/kg, i.p.) at one of several time points from 1 h to 23 days. The data reveal that neither acute nor chronic pegIFN-alpha induced corticosterone release. Overall, the current report demonstrates that neither acute nor chronic IFN-alpha induced depressive-like behavior and neither IFN-alpha nor peg-IFN-alpha was capable of inducing neuroendocrine or neuroimmune activation. Despite the neurochemical alterations observed in the chronic treatment regimen, the data indicate that recombinant human IFN-alpha does not produce a robust model of depressive-like behavior in rodents.     

Expression of the multidrug transporter MRP2 in the blood-brain barrier after pilocarpine-induced seizures in rats

Multidrug resistance proteins (MRPs; symbol ABCC) are membrane glycoproteins that mediate the ATP-dependent export of a wide range of substrates from cells and thereby affect the bioavailability and disposition of many drugs. MRP2 (ABCC2) is expressed on the apical domain of hepatocytes, enterocytes of the proximal small intestine, and proximal renal tubular cells, but its location in the brain is a matter of debate. Most previous studies failed to determine MRP2 mRNA or protein in the brain or cell preparations from the brain of different species including humans. Based on our previous experience with the drug efflux transporter P-glycoprotein, we evaluated whether the immunohistochemical determination of MRP2 expression is sensitive to fixation and staining variables. Furthermore, we examined whether the MRP2 protein is overexpressed after experimentally induced seizures in rats, using the pilocarpine model of temporal lobe epilepsy. The MRP2 expression in the liver was used as positive control. MRP2 deficient TR- rats were used as negative controls. Despite various modifications in tissue fixation and immunohistochemical staining as well as use of different commercially available MRP2 antibodies, we never observed any unequivocal MRP2 staining in the brain of normal rats. However, after a pilocarpine-induced convulsive status epilepticus, clear MRP2 staining became visible in brain capillary endothelial cells and, less frequently, perivascular astroglia and neurons in various brain regions. In view of our recent data on brain access of antiepileptic drugs in MRP2 deficient TR- rats, seizure-induced over-expression of MRP2 in the blood-brain barrier is likely to impair drug penetration into the brain, thereby contributing to drug resistance in epilepsy.     

Muscarinic mobilization of choline in rat cerebral cortex does not involve alterations of blood-brain barrier

Efflux of choline from the rat cerebral cortex in vivo was investigated using the cup technique. After removal of the dura mater, the cup was placed on the cortex. Transmission and scanning electron microscopy revealed that the cortex was separated from the cup solution (100-300 microliter) by basal lamina, pia mater, arachnoid (with discrete defects) and remainders of the subdural neurothelium. Two kinds of experiments were carried out to determine: efflux of unlabelled choline into the cup solution; and translocation of radioactivity from the plasma into the cup solution (via blood-brain barrier and leptomeningeal layers) during i.v. infusion of [3H]choline or [14C]inulin. The former process was highly temperature-sensitive in contrast to the latter. Penicillin-G-sodium, which is known to damage the blood-brain barrier, was added to the cup solution, enhanced efflux of unlabelled choline, and caused a 5-fold increase in the rates of translocation of radioactivity during infusion of either labelled choline or inulin. In contrast, physostigmine (3 X 10(-4) M, added to cup solution) failed to enhance 3H-translocation, but markedly facilitated the efflux of unlabelled choline; this effect was highly temperature-sensitive and was blocked by atropine. It is concluded that activation of muscarinic receptors enhanced the choline efflux from cortical tissue. This effect was caused by cellular mobilization of choline presumably through an action on the metabolism of phosphatidylcholine. The effect was not due to alterations in the translocation of choline from the plasma to the cup solution, i.e. through permeability changes in the blood-brain barrier and in the leptomeningeal 'barrier'.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of integrin alphavbeta3 reduces blood-brain barrier breakdown in focal ischemia in rats

Ischemic stroke is a major cause of morbidity and mortality in industrialized nations. We tested the effect of postischemic treatment of cyclo-RGDfV (cRGDfV), a selective inhibitor of integrin alphavbeta3, in the middle cerebral artery occlusion (MCAO) model of ischemic stroke in rats. Rats were randomly divided into three groups: sham operation (n = 13), MCAO with no treatment (n = 18), and MCAO with cRGDfV treatment (n = 28). Focal ischemia was induced with the suture occlusion method for 2 hr, and treatment was given 1 hr after reperfusion (3 hr after ischemia). All animals were sacrificed 24 hr after reperfusion. Assessment included neurological scores, infarction volumes, brain water content, Evans blue exudation, IgG exudation, histology, immunohistochemistry, and Western blotting. Treatment with cRGDfV ameliorated neurological deficits, reduced brain edema, and reduced exudation of Evans blue dye and IgG, but failed to reduce infarction volumes. Western blotting showed a reduction in phosphorylation of one subset of vascular endothelial growth factor (VEGF) receptors in the cRGDfV treatment group. Western blotting also demonstrated a significant reduction of fibrinogen in the cRGDfV treatment group. We conclude that poststroke treatment with cRGDfV reduces blood-brain barrier breakdown in focal ischemia, possibly through inhibition of VEGF-mediated vascular breakdown.     

The antiepileptic drug mephobarbital is not transported by P-glycoprotein or multidrug resistance protein 1 at the blood-brain barrier: a positron emission tomography study

Aim of this study was to determine whether the carbon-11-labeled antiepileptic drug [(11)C]mephobarbital is a substrate of P-glycoprotein (Pgp) and can be used to assess Pgp function at the blood-brain barrier (BBB) with positron emission tomography (PET). We performed paired PET scans in rats, wild-type (FVB) and Mdr1a/b((-/-)) mice, before and after intravenous administration of the Pgp inhibitor tariquidar (15mg/kg). Brain-to-blood AUC(0-60) ratios in rats and brain AUC(0-60) values of [(11)C]mephobarbital in wild-type and Mdr1a/b((-/-)) mice were similar in scans 1 and 2, respectively, suggesting that in vivo brain distribution of [(11)C]mephobarbital is not influenced by Pgp efflux. Absence of Pgp transport was confirmed in vitro by performing concentration equilibrium transport assay in cell lines transfected with MDR1 or Mdr1a. PET experiments in wild-type mice, with and without pretreatment with the multidrug resistance protein (MRP) inhibitor MK571 (20mg/kg), and in Mrp1((-/-)) mice suggested that [(11)C]mephobarbital is also not transported by MRPs at the murine BBB, which was also supported by in vitro transport experiments using human MRP1-transfected cells. Our results are surprising, as phenobarbital, the N-desmethyl derivative of mephobarbital, has been shown to be a substrate of Pgp, which suggests that N-methylation abolishes Pgp affinity of barbiturates.     

Excessive oxygen or glucose supply does not alter the blood flow response to somatosensory stimulation or spreading depression in rats

We investigated the influence of hyperoxia (arterial pO₂ 446 ± 43 mmHg) and hyperglycemia (blood glucose 19.4 mmol/l) on somatosensory stimulation (whisker deflection) employing laser Doppler flowmetry (LDF). Our aim was to test the hypothesis that a possible substrate-sensing mechanism for glucose and oxygen contributes to the coupling between cortical activity and regional cerebral blood flow (rCBF) in order to match increased demand with substrates. In addition, we looked at the influence of hyperglycemia (blood glucose 17.9 mmol/l) and hypercapnia (arterial pCO₂ 62 mmHg) on rCBF (LDF) and regional cerebral blood oxygenation changes (rCBO) in the even stronger metabolic stimulus of cortical spreading depression (CSD). For the latter we employed the new non-invasive technique of near infrared spectroscopy (NIRS). All experiments were done using chloralose/urethane-anesthetized rats. Somatosensory stimulation increased rCBF by about 20% of baseline, in the case of both norm- and hyperoxia as well as both normo- and hyperglycemia. The blood-flow response to CSD consisted of a temporary sharp increase in rCBF to more than 400%. At the same time, the concentration of oxyhemoglobin [HbO₂] increased, while deoxyhemoglobin [Hb] decreased, indicating excessive oxygenation. Hyperglycemia altered neither the rCBF nor the rCBO response. Preexisting hypercapnia, however, produced reductions in both hyperperfusion (rCBF) and hyperoxygenation (rCBO) during CSD. We found that, for experimental hyperglycemia, i.v. may be superior to i.p. application of glucose because of the latter's side effects in connection with blood flow. Our findings cannot support the hypothesis of a substrate sensing mechanism in coupling.     

Repeated administration of the novel antiepileptic agent levetiracetam does not alter digoxin pharmacokinetics and pharmacodynamics in healthy volunteers.

OBJECTIVE: This study was undertaken to determine whether levetiracetam (Keppra) affected the pharmacokinetic or pharmacodynamic profile of digoxin in healthy adults. METHODS: Seven men and four women (19-48 years old) completed this double-blind, placebo-controlled study. Each received digoxin 0.25 mg once daily (0.5 mg on day 1) during the 1-week run-in period, followed by two 1-week periods of coadministration of digoxin with levetiracetam (2000 mg/day) or placebo in a two-way crossover design. The pharmacokinetics of digoxin and levetiracetam were assessed by analysis of blood samples. ECG recordings were taken to monitor effects of levetiracetam on digoxin pharmacodynamics. RESULTS: The ratios of geometric means, using a 90% confidence interval, between coadministration of digoxin with levetiracetam or placebo were 103.96% (99.18%, 108.95%) for AUC(ss), 100.87% (89.52%, 113.66%) for C(max), 97.67% (82.76%, 115.26%) for PTF, and 99.04% (90.98%, 109.00%) for C(min). Although digoxin produced predictable changes in ECG, its pharmacodynamic parameters did not differ significantly between levetiracetam and placebo administration. Furthermore, the pharmacokinetics of levetiracetam were not altered in the presence of digoxin. Co-administration of levetiracetam and digoxin was well tolerated. CONCLUSION: At the doses administered, there was no pharmacokinetic interaction and no evidence of a pharmacodynamic interaction between digoxin and levetiracetam.     

Sleep-related brain activation does not increase the permeability of the blood-brain barrier to glucose.

We compared blood-brain barrier (BBB) permeability to glucose between quiet wakefulness and rapid-eye-movement (REM) sleep to assess whether changes in BBB permeability play a role in coupling glucose supply to the physiologic metabolic needs of the brain. Male Sprague-Dawley rats were prepared with electrodes for wake-sleep state scoring and with arterial and venous catheters. Using the single-pass, dual-label indicator method, unidirectional glucose extraction by the brain and cerebral blood flow (CBF) were simultaneously measured during states of quiet wakefulness (n=12) or REM sleep (n=7). The product of BBB surface area and permeability to glucose (PS product) was computed in each state. During REM sleep, CBF significantly exceeded that during quiet wakefulness in all regions but the cerebellum, whereas the difference in the PS product between quiet wakefulness and REM sleep was not statistically significant in any brain region. In the brain as a whole, CBF significantly increased 29% from quiet wakefulness to REM sleep, while a nonsignificant 0.8% increase occurred in the PS product. During REM sleep, the increase in CBF indicates a higher rate of brain glucose consumption than in quiet wakefulness, given the tight flow-metabolism coupling in the brain. Therefore, these data show that modulation of BBB permeability to glucose is not a mechanism that provides 'energy on demand' during the physiologic brain activation characterising REM sleep.     

Stereoselective blood-brain barrier transport of histidine in rats

The transport characteristics of - and -histidine through the blood-brain barrier (BBB) were studied using cultured rat brain microvascular endothelial cells (BMEC). -Histidine uptake was a saturable process. A decrease in incubation temperature from 37 to 0°C or the addition of metabolic inhibitors (DNP and rotenone) reduced the uptake rate of -histidine. Ouabain, an inhibitor of (Na⁺, K⁺)-ATPase, also reduced uptake of -histidine. Moreover, the substitution of Na⁺ with choline chloride and choline bicarbonate in the incubation buffer decreased the initial - and -histidine uptake rates. These results suggested that -histidine is actively uptaken by a carrier-mediated mechanism into the BMEC, with energy supplied by Na⁺. However, -histidine uptake at 0°C was not completely inhibited, and it was reduced in the presence of an Na⁺-independent System-L substrate, BCH, suggesting facilitated diffusion (the Na⁺-independent process) by a carrier-mediated mechanism into the BMEC. -histidine uptake in rat BMEC also appeared to be System-N mediated since uptake was inhibited by glutamine, aspargine and -glutamic acid γ-monohydroxamate. System-N mediated transport was not pH sensitive. -histidine transport was also studied in rat BMEC. -histidine transport by rat BMEC has similar characteristics to -histidine. However, System-N transport did not play a role in -histidine uptake. The uptake of -histidine was also greater than that of the -isomer, indicating the stereoselective uptake of histidine in rat BMEC.     

Proteasome or calpain inhibition does not alter cellular tau levels in neuroblastoma cells or primary neurons

Impaired tau catabolism may contribute to tau accumulation and aggregation in Alzheimer's disease and neurofibrillary tangle formation. This study examined the effects of proteasome and calpain inhibition on tau levels and turnover in primary rat hippocampal neurons and differentiated SH-SY5Y human neuroblastoma cells. Administration of proteasome (MG-115, lactacystin) or calpain (MDL28170) inhibitors for up to 24 hours did not alter tau levels in differentiated SH-SY5Y cells or rat hippocampal neurons. Addition of 1 microM and 10 microM MG-115 did not change total tau levels, but did result in increased reactivity of phosphorylation-dependent tau antibodies (PHF-1, CP-13) and decreased Tau-1 immunoreactivity. Administration of cycloheximide to inhibit de novo protein synthesis also did not alter tau levels in the presence or absence of lactacystin. These results demonstrate that although the proteasome and calpain protease systems are capable of degrading tau in cell-free assays, their inhibition does not alter cellular tau levels in primary neurons or differentiated neuroblastoma cells.     

Substance P does not alter interleukin-1 expression by splenic or granuloma macrophages in murine schistosomiasis.

Substance P (SP) is an undecapeptide with neurotransmitter and immunoregulatory properties. In murine schistosomiasis, ova naturally induce liver and intestinal granulomas. These granulomas contain macrophages, and eosinophils that produce SP. A report showed that human blood monocytes isolated by adherence release interleukin-1 (IL-1) in response to SP (Lotz et al. (1989) Science 241, 1218). IL-1 is important for initiation of hypersensitivity granulomas. Therefore, it was determined whether SP modulates granuloma macrophage IL-1 production in murine schistosomiasis. Macrophages were obtained from lung and liver granulomas, and from spleens of infected mice. A thymocyte proliferation assay measured IL-1 activity in culture supernatants. Total RNA, extracted from macrophages, was assayed for IL-1 alpha and beta mRNA by Northern blotting using cDNA probes. In response to lipopolysaccharide (LPS), splenic macrophages and macrophages from young lung granulomas released appreciable IL-1. Macrophages from liver granulomas, that were lesions older than the lung granulomas, were unresponsive to LPS with regard to IL-1 secretion. Yet, granuloma macrophages spontaneously expressed IL-1 alpha and beta mRNA. LPS enhanced IL-1 mRNA expression in both splenic and granuloma macrophages. Exposure of macrophages from all sources to SP did not alter IL-1 secretion or gene expression. Similarly, the responsiveness of macrophages to LPS was not affected by concomitant exposure to SP. It is concluded that, in the murine system, SP does not directly influence splenic or granuloma macrophage IL-1 secretion or gene expression. Also, it appears that macrophage secretion of IL-1 is rapidly down-regulated following granuloma elicitation.     

Inhibition of mammalian target of rapamycin reduces epileptogenesis and blood-brain barrier leakage but not microglia activation

Purpose: Previous studies have shown that inhibition of the mammalian target of rapamycin (mTOR) pathway with rapamycin prevents epileptogenesis after pharmacologically induced status epilepticus (SE) in rat models of temporal lobe epilepsy. Because rapamycin is also known for its immunosuppressant properties we hypothesized that one of the mechanisms by which it exerts this effect could be via suppression of brain inflammation, a process that has been suggested to play a major role in the development and progression of epilepsy. Methods: Rats were treated with rapamycin or vehicle once daily for 7 days (6 mg/kg/day, i.p.) starting 4 h after the induction of SE, which was evoked by electrical stimulation of the angular bundle. Hereafter rapamycin was administered every other day until rats were sacrificed, 6 weeks after SE. Video‐electroencephalography was used to monitor the occurrence of seizures. Neuronal death, synaptic reorganization, and microglia and astrocyte activation were assessed by immunohistologic staining. Fluorescein was administered to quantify blood–brain barrier leakage. Key Findings: Rapamycin treatment did not alter SE severity and duration compared to vehicle treatment rats. Rapamycin‐treated rats developed hardly (n = 9) or no (n = 3) seizures during the 6‐week treatment, whereas vehicle‐treated rats showed a progressive increase of seizures starting 1 week after SE (mean 8 ± 2 seizures per day during the sixth week). Cell loss and sprouting that normally occur after SE were prominent but on average significantly less in rapamycin‐treated rats versus vehicle‐treated rats. Nevertheless, various inflammation markers (CD11b/c and CD68) were dramatically upregulated and not significantly different between post‐SE groups. Of interest, blood–brain barrier leakage was barely detected in the rapamycin‐treated group, whereas it was prominent in the vehicle‐treated group. Significance: mTOR inhibition led to strong reduction of seizure development despite the presence of microglia activation, suggesting that effects of rapamycin on seizure development are not due to a control of inflammation. Whether the effects on blood–brain barrier leakage in rapamycin‐treated rats are a consequence of seizure suppressing properties of the drug, or contribute to a real antiepileptogenic effect still needs to be determined.     

Sub-chronic antipsychotic drug treatment does not alter brain phospholipid fatty acid composition in rats

Altered membrane phospholipid fatty acid composition is reported in schizophrenia and appears to be reduced by antipsychotic drug treatment. To determine whether antipsychotic drugs have a direct effect on brain phospholipid fatty acid composition, the effects of sub-chronic treatment with a "typical" and an "atypical" antipsychotic drug were determined in adult male Sprague-Dawley rats. Rats were treated with haloperidol (1 mg/kg), clozapine (20 mg/kg) or vehicle daily for 21 days. Whole brain total phospholipid composition was determined by gas chromatography. No alterations in brain phospholipid composition were produced by either drug. This suggests that the apparent normalization of membrane phospholipids observed in drug-treated schizophrenic patients is not due to a direct pharmacological effect of these drugs nor can the pharmacological effects of these drugs occurring in this time frame be attributed to alterations in neuronal membrane fatty acid composition.     

Whole-body exposure to 2.45 GHz electromagnetic fields does not alter radial-maze performance in rats

Mobile communication is based on utilization of electromagnetic fields (EMFs) in the frequency range of 0.3-300 GHz. Human and animal studies suggest that EMFs, which are in the 0.1 MHz-300 GHz range, might interfere with cognitive processes. In 1994, a report by Lai et al. [Bioelectromagnetics 15 (1994) 95-104] showed that whole-body exposure of rats to pulsed 2.45 GHz microwaves (2 micros pulse width, 500 pps, and specific absorption rate [SAR] 0.6 W/kg) for 45 min resulted in altered spatial working memory assessed in a 12-arm radial-maze task. Surprisingly, there has been only one attempt to replicate this experiment so far [Bioelectromagnetics 25 (2004) 49-57]; confirmation of the Lai et al. experiment failed. In the present study, rats were tested in a 12-arm radial-maze subsequently to a daily exposure to 2.45 GHz microwaves (2 micros pulse width, 500 pps, and SAR 0.6 W/kg) for 45 min. The performance of exposed rats was comparable to that found in sham-exposed or in naive rats (no contact with the exposure system). Regarding the methodological details provided by Lai et al. on their testing protocol, our results might suggest that the microwave-induced behavioral alterations measured by these authors might have had more to do with factors liable to performance bias than with spatial working memory per se.