Neuroprotective effect of lamotrigine and MK-801 on rat brain lesions induced by 3-nitropropionic acid: evaluation by magnetic resonance imaging and in vivo proton magnetic resonance spectroscopy

Magnetic resonance imaging and in vivo proton magnetic resonance spectroscopy were used to evaluate the therapeutic effect of lamotrigine and MK-801 on rat brain lesions induced by 3-nitropropionic acid. Systemic administration of 3-nitropropionic acid (15 mg/kg per day) to two-month-old Sprague-Dawley rats (n = 10 for each group) for five consecutive days induced selective striatal and hippocampal lesions and specific behavioral change. Pretreatment with lamotrigine (10 mg/kg or 20 mg/kg per day) or MK-801 (2 mg/kg per day) attenuated the lesions and behavioral change. There were no significant differences in T2 values of the striatum and hippocampus among rats pretreated with MK-801, lamotrigine (20 mg/kg) and sham controls. Significant elevations of succinate/creatine and lactate/creatine ratios and decreases of N-acetylaspartate/creatine and choline/creatine ratios were observed after 3-nitropropionic acid injections (P < 0.001). The changes were nearly prevented after pretreatment with lamotrigine (20 mg/kg). However, the N-acetylaspartate/creatine in rats pretreated with lamotrigine (10 mg/kg) (P < 0.01) and MK-801 (P < 0.05) still showed significant reduction as compared with sham controls. Thus we conclude that both lamotrigine and MK-801 are effective in attenuation of brain lesions induced by 3-nitropropionic acid. A higher dose of lamotrigine provides a better neuroprotective effect than MK-801. With a better therapeutic effect and fewer side effects, lamotrigine is more promising for potential clinical application.     

Magnetic resonance imaging and spectroscopy in assessing 3-nitropropionic acid-induced brain lesions: an animal model of Huntington's disease

Huntington's disease (HD) is an inherited neurodegenerative disease, in which there is progressive motor and cognitive deterioration, and for which the pathogenesis of neuronal death remains controversial. Mitochondrial toxins like 3-nitropropionic acid (3-NP) and malonate, functioning as the inhibitors of the complex II of mitochondrial respiratory chain, have been found to effectively induce specific behavioral changes and selective striatal lesions in rats and non-human primates mimicking those in HD. Furthermore, several kinds of transgenic mouse models of HD have been recently developed, and used in the development and assessment of novel treatments for HD. In the past, most studies evaluating the animal models for HD were based on histological changes or in vitro neuronal cultures. With the emergence of advanced magnetic resonance technologies, non-invasive magnetic resonance imaging (MRI) and spectroscopy provide more detail of cerebral alterations, including the changes of cerebral structure, function and metabolites. These studies support the hypothesis that mitochondrial dysfunction with increased excitation of N-methyl-D-aspartate (NMDA) receptors can replicate the neurobehavioral changes, selective brain injury and neurochemical alterations in HD. The present review focuses on our work as well as that of others regarding 3-NP-induced neurotoxicity and other animal models of HD. Using both conventional and advanced MRI and spectroscopy, we summarize the pathogenesis and possible therapeutic strategies in chemical and transgenic models of HD. The results show magnetic resonance techniques to be powerful techniques in the evaluation of pathogenesis and therapeutic intervention for both chemical and transgenic models of HD.     

MK-801和Nimodipine对感染性脑水肿的影响

目的和方法：观察百日咳菌液诱导的感染性脑水肿不同时间大鼠脑含水量和伊文思兰（ＥＢ）含量的变化,以及ＮＫ－８０１预处理和尼莫地平对感染性脑水肿脑含水量和ＥＢ含量的影响。结果：感染性脑水肿在注菌后３０ｍｉｎ,脑含水量和ＥＢ含量已明显升高,应用ＭＫ－８０１预处理或ｎｉｍｏｄｉｐｉｎｅ治疗后,脑组织含水量和ＥＢ含量显著降低,脑水肿明显减轻。     

Correlation between near-infrared spectroscopy and magnetic resonance imaging of rat brain oxygenation modulation

We measure the tissue oxygen and haemoglobin concentrations in the rat brain during modulation of inhaled oxygen concentration (FiO2), using non-invasive frequency domain near-infrared oximetry. The rise in oxygenated haemoglobin concentration and the decline in deoxygenated haemoglobin concentration are demonstrated in correspondence with the modulation of FiO2, which is changed from 20% to 100% in increments of 20%. Furthermore, the tissue oxygenation saturation also shows the corresponding trend and changes ranging from approximately 70% to 90%. The relative changes in deoxygenated haemoglobin concentration are compared to the blood-oxygenation-level-dependent (BOLD) MRI signal recorded during a similar FiO2 protocol. A linear relationship with high correlation coefficient between the relative changes in the BOLD MRI signal and the NIRS signal is observed.     

Temporal evolution of 3-nitropropionic acid-induced neurodegeneration in the rat brain by T2-weighted, diffusion-weighted, and perfusion magnetic resonance imaging.

An appropriate detecting technique is necessary for the early detection of neurodegenerative diseases. 3-Nitropropionic acid-intoxicated rats serve as the animal model for one neurodegenerative disease, Huntington's disease. Non-invasive diffusion- and T2-weighted magnetic resonance imaging were applied to study temporal evolution and spatial distribution of brain lesions which were produced by intravenous injection of 3-nitropropionic acid in rats. Lesions in the striatum, hippocampus, and corpus callosum but not in the cortex were observed 3 and 4.5 h after 3-nitropropionic acid injection (30 mg/kg) on the diffusion- and T2-weighted images, respectively (n = 6). The results demonstrated that the diffusion-weighted imaging is not only superior to T2-weighted imaging in detecting onset of 3-nitropropionic acid-induced excitotoxic brain damage but also differentiates lesion and non-lesion areas with better spatial resolution than T2-weighted imaging. Additionally, to correlate structural alterations with pathophysiological conditions, dynamic susceptibility contrast magnetic resonance imaging was performed before and 4 h after 3-nitropropionic acid administration (n = 8). The relative cerebral blood volume was significantly elevated in the striatum (P < 0.001) but not in the cortex after 3-nitropropionic acid administration. The changes in regional relative cerebral blood volume were well correlated to the changes in signal intensities in the corresponding areas on the diffusion- and T2-weighted images. The combined structural and functional information in this study may provide new insights and therapeutic strategies in treating neurodegenerative diseases.     

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

The purpose of this paper is to facilitate the comparison of magnetic resonance (MR) spectra acquired from unknown brain lesions with published spectra in order to help identify unknown lesions in clinical settings. The paper includes lists of references for published MR spectra of various brain diseases, including pyogenic abscesses, encephalitis (herpes simplex, Rasmussen's and subacute sclerosing panencephalitis), neurocysticercosis, tuberculoma, cysts (arachnoid, epidermoid and hydatid), acute disseminated encephalomyelitis (ADEM), adrenoleukodystrophy (ALD), Alexander disease, Canavan's disease, Krabbe disease (globoid cell leukodystrophy), Leigh's disease, megalencephalic leukoencephalopathy with cysts, metachromatic leukodystrophy (MLD), Pelizaeus-Merzbacher disease, Zellweger syndrome, HIV-associated lesions [cryptococcus, lymphoma, toxoplasmosis and progressive multifocal leukoencephalopathy (PML)], hydrocephalus and tuberous sclerosis. Each list includes information on the echo time(s) (TE) of the published spectra, whether a control spectrum is shown, whether the corresponding image and voxel position are shown and the patient ages if known. The references are listed in the approximate order of usefulness, based on spectral quality, number of spectra, range of echo times and whether the voxel positions are shown. Spectra of Zellweger syndrome, cryptococcal infection, toxoplasmosis and lymphoma are included, along with a spectrum showing propanediol (propylene glycol).     

Monitoring cytotoxic tumour treatment response by diffusion magnetic resonance imaging and proton spectroscopy

Exposure of tumours to anti-cancer drugs, gene or radiation therapy consistently leads to an increase in water diffusion in the cases expressing favourable treatment response. The diffusion change coincides cytotoxic cell eradication and precedes volume reduction in drug or gene therapy-treated experimental tumours. Interestingly, the recent studies from human brain tumour patients undergoing chemotherapy show similar behaviour of diffusion, suggesting important application for MRI in patient management. In this review observations from diffusion MRI and MRS in the tumours during cytotoxic treatment are summarized and the cellular mechanisms affecting molecular mobility are discussed in the light of tissue microenvironmental and microdynamic changes.     

In vivo monitoring of age-related changes in rat brain using quantitative diffusion magnetic resonance imaging and magnetic resonance relaxometry

Ghrelin is a novel peptide that stimulates the release of growth hormone from the pituitary and is involved in hypothalamic feeding regulation. A pre-embedding immunostaining technique was used to study the ultrastructure and synaptic relationships of ghrelin-containing neurons in the rat arcuate nucleus (ARC). Ghrelin-like immunoreactive (ghrelin-LI) neurons were found in the ARC, and were especially abundant in its ventral part. At the electron microscopic level, ghrelin-LI neurons received afferent synapses from many unknown axon terminals. Ghrelin-LI products in the immunoreactive cell bodies, processes, and axon terminals were detected mainly in dense granular vesicles about 110 nm in diameter. Ghrelin-LI presynaptic axon terminals often made synapses with unknown immunonegative neurons. These results suggest that ghrelin acts to regulate food intake through synaptic connections in hypothalamic neuronal networks.     

In vivo chlorine‐35, sodium‐23 and proton magnetic resonance imaging of the rat brain

In this study we demonstrate the feasibility of combined chlorine‐35, sodium‐23 and proton magnetic resonance imaging (MRI) at 9.4 Tesla, and present the first in vivo chlorine‐35 images obtained by means of MRI. With the experimental setup used in this study all measurements could be done in one session without changing the setup or moving the subject. The multinuclear measurement requires a total measurement time of 2 h and provides morphological (protons) and physiological (sodium‐23, chlorine‐35) information in one scanning session. Chlorine‐35, sodium‐23 and high resolution proton images were acquired from a phantom, a healthy rat and from a rat displaying a focal cerebral infarction. Compared to the healthy tissue a signal enhancement of a factor of 2.2 ± 0.2 in the chlorine‐35 and a factor of 2.9 ± 0.6 in the sodium‐23 images is observed in the areas of infarction. Exemplary unlocalized measurement of the in vivo longitudinal and transversal relaxation time of chlorine‐35 in a healthy rat showed multi‐exponential behaviour. A biexponential fit revealed a fast and a slow relaxing component with T_1,a = (1.7 ± 0.4) ms, T_1,b = (25.1 ± 1.4) ms, amplitudes of A = 0.26 ± 0.02, (1–A) = 0.74 ± 0.02 and T_2,a = (1.3 ± 0.1) ms, T_2,b = (11.8 ± 1.1) ms, A = 0.64 ± 0.02, (1–A) = 0.36 ± 0.02. Combined proton, sodium‐23 and chlorine‐35 MRI may provide a new approach for non‐invasive studies of ionic regulatory processes under physiological and pathological conditions in vivo. Copyright © 2010 John Wiley & Sons, Ltd.     

Dose-dependent effect of MK-801 on the levels of neuropeptides processing enzymes in rat brain regions

The appropriate levels of neuropeptides and their processing enzyme activities are required to continue a normal cell life, and the dysfunction of these peptides and enzymes are responsible for many neuronal abnormalities. Systemic administration of (+) MK-801 (dizocilpine maleate), a noncompetitive N-methyl-[D]-aspartate (NMDA) receptor antagonist, causes both neuroprotective and neurotoxic activities depending on doses and conditions. In the present study, we investigated the dose dependent effect of (+) MK-801 on prolyl endopeptidase (PEP), endopeptidase EC 24.15 (EP 24.15) and beta-D-glucuronidase activities as well as the protein levels of EP 24.15 and neuron specific enolase (NSE) in the posterior cingulate/retrosplenial cortices (PC/RSC), hippocampus, frontal cortex and striatum of female rats 3 days after the treatment. The activity of PEP was significantly increased compared with controls (saline) in the PC/RSC at 1.0 and 5.0 mg/kg doses, and in the frontal cortex at 5.0 mg/kg dose. beta-D-Glucuronidase activity was dose-dependently increased in all brain regions examined. The activity of EP 24.15 was unchanged in all regions after the treatment, whereas the Western blot analysis for EP 24.15 showed the increased protein level in the PC/RSC. These results suggest that a low dose treatment with MK-801 causes neurotoxicity in the PC/RSC and hippocampus, and the high dose treatment causes neurotoxicity in all the brain regions examined.     

MK-801 prevents brain lesions and delayed-nonmatching-to-sample deficits produced by pyrithiamine-induced encephalopathy in rats.

Rats were trained on a spatial delayed-nonmatching-to-sample (DNMTS) task and assigned by block randomization to one of four treatments: pyrithiamine-induced thiamine deficiency (PTD), PTD with administration of MK-801 after 12 days, control with MK-801 treatment, and control without MK-801. After 15 days of treatment followed by 21 days of recovery, the PTD rats showed significant deficits for DNMTS accuracy at retention intervals (RI) that ranged from 3.0 s to 15.0 s, the RIs that produced 75% accuracy on DNMTS in staircase training, and the rate at which a novel radial arm maze task was learned. The PTD-treated rats had consistent lesions in the thalamus and the mammillary bodies. MK-801 protected rats from both behavioral deficits and brain lesions (assessed quantitatively and qualitatively) that were produced by the PTD treatment.     

Effect of transcranial magnetic stimulation on oxidative stress induced by 3-nitropropionic acid in cortical synaptosomes

This study evaluates the effect of transcranial magnetic stimulation (TMS; 60 Hz and 0.7 mT) treatment on 3-nitropropionic acid (20 mg/kg i.p./day for 4 days)-induced oxidative stress in cortical synaptosomes of Wistar rats. The oxidative derangement was confirmed by a high level of lipid peroxidation products and protein carbonyls, together with a decreased in reduced glutathione (GSH) content, catalase and GSH-peroxidase (GSH-Px) activities. Additionally, it was observed a reduction in succinate dehydrogenase (SDH) activity. All changes were partially prevented or reversed by administration of TMS. These results show that TMS reduces oxidative stress in cortical synaptosomes, and suggest that TMS may protect neuronal and maintain synaptic integrity.     

Wavelet compression on detection of brain lesions with magnetic resonance imaging

The purpose of this report is to assess clinically acceptable compression ratios on the detection of brain lesions at magnetic resonance imaging (MRI). Four consecutive T2-weighted and the corresponding T1-weighted images obtained in 20 patients were studied for 109 anatomic sites including 50 with lesions and 59 without lesions. The images were obtained on a 1.5-T MR unit with a pixel size of 0.9 to 1.2 x 0.47 mm and a section thickness of 5 mm. The image data were compressed by wavelet-based algorithm at ratios of 20:1, 40:1, and 60:1. Three radiologists reviewed these images on an interactive workstation and rated the presence or absence of a lesion with a 50 point scale for each anatomic site. The authors also evaluated the influence of pixel size on the quality of image compression. At receiver operating characteristic (ROC) analysis, no statistically significant difference was detected at a compression ratio of 20:1. A significant difference was observed with 40:1 compressed images for one reader (P = .023), and with 60:1 for all readers (P = .001 to .012). A root mean squared error (RMSE) was higher in 0.94- x 0.94-mm pixel size images than in 0.94- x 0.47-mm pixel size images at any compression ratio, indicating compression tolerance is lower for the larger pixel size images. The RMSE, subjective image quality, and error images of 10:1 compressed 0.94- x 0.94-mm pixel size images were comparable with those of 20:1 compressed 0.94- x 0.47-mm pixel size images. Wavelet compression can be acceptable clinically at ratios as high as 20:1 for brain MR images when a pixel size at image acquisition is around 1.0 x 0.5 mm, and as high as 10:1 for those with a pixel size around 1.0 x 1.0 mm.     

Neuroprotective effect of L-carnitine in the 3-nitropropionic acid (3-NPA)-evoked neurotoxicity in rats

A plant and fungal toxin, 3-NPA, acts as an inhibitor of mitochondrial function via irreversible inactivation of the mitochondrial inner membrane enzyme, succinate dehydrogenase (SDH). Inhibition of SDH disturbs electron transport and leads to cellular energy deficits and neuronal injury. We have shown that pretreatment with l-carnitine, while not significantly attenuating SDH inhibition, prevented hypothermia and oxidative stress-associated increased activity of free radical-scavenging enzymes. Here, a neurohistological method was applied to examine the effect of carnitine pretreatment against 3-NPA-induced neurotoxicity. Twenty adult male Sprague-Dawley rats were randomly divided into two groups (n = 10/group). Rats in the first group were injected twice with 3-NPA at 30 mg/kg s.c., 2 days apart, and the second group of animals received l-carnitine pretreatment at 100 mg/kg 30-40 min before 3-NPA administration. Rats in both groups were perfused 7 days later and their brains harvested. Degenerating neurons were identified and localized via the fluorescent marker Fluoro-Jade B. In the three animals that survived 3-NPA dosing, one exhibited no pathology, one exhibited moderate unilateral damage to the striatum, and the third exhibited extensive bilateral neuronal degeneration in multiple forebrain regions. In the seven surviving animals that received l-carnitine prior to 3-NPA insult, six exhibited no lesions, while one exhibited a modest unilateral lesion in the striatum. It appears that l-carnitine is protective against 3-NPA-induced toxicity, as reflected by both reduced mortality and significantly reduced neuronal degeneration.     

Improving the reproducibility of proton magnetic resonance spectroscopy brain thermometry: Theoretical and empirical approaches

In proton magnetic resonance spectroscopy (¹H MRS)-based thermometry of brain, averaging temperatures measured from more than one reference peak offers several advantages, including improving the reproducibility (i.e., precision) of the measurement. This paper proposes theoretically and empirically optimal weighting factors to improve the weighted average of temperatures measured from three references. We first proposed concepts of equivalent noise and equivalent signal-to-noise ratio in terms of frequency measurement and a concept of relative frequency that allows the combination of different peaks in a spectrum for improving the precision of frequency measurement. Based on these, we then derived a theoretically optimal weighting factor and proposed an empirical weighting factor, both involving equivalent noise levels, for a weighted average of temperatures measured from three references (i.e., the singlets of NAA, Cr, and Ch in the ¹H MR spectrum). We assessed these two weighting factors by comparing their errors in measurement of temperatures with the errors of temperatures measured from individual references; we also compared these two new weighting factors with two previously proposed weighting factors. These errors were defined as the standard deviations in repeated measurements or in Monte Carlo studies. Both the proposed theoretical and empirical weighting factors outperformed the two previously proposed weighting factors as well as the three individual references in all phantom and in vivo experiments. In phantom experiments with 4- or 10-Hz line broadening, the theoretical weighting factor outperformed the empirical one, but the latter was superior in all other repeated and Monte Carlo tests performed on phantom and in vivo data. The proposed weighting factors are superior to the two previously proposed weighting factors and can improve the reproducibility of temperature measurement using ¹H MRS-based thermometry.     

Investigation of human brain hemodynamics by simultaneous near-infrared spectroscopy and functional magnetic resonance imaging

The aim of this study was to compare functional cerebral hemodynamic signals obtained simultaneously by near infrared spectroscopy (NIRS) and by functional magnetic resonance imaging (fMRI). The contribution of superficial layers (skin and skull) to the NIRS signal was also assessed. Both methods were used to generate functional maps of the motor cortex area during a periodic sequence of stimulation by finger motion and rest. In all subjects we found a good collocation of the brain activity centers revealed by both methods. We also found a high temporal correlation between the BOLD signal (fMRI) and the deoxy-hemoglobin concentration (NIRS) in the subjects who exhibited low fluctuations in superficial head tissues.     

MK-801 induces c-fos protein in thalamic and neocortical neurons of rat brain

MK-801, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, leads to a dramatic induction of c-fos-like protein in neurons in deep layers of the neocortex, in dorsal and ventral midline thalamic nuclei and in neurons in the central grey of rat brain. This induction of c-fos by MK-801 is dose-and time-dependent occurring within 2 h and dissipating by 24 h after injection (0.5-8.0 mg/kg, i.p.). The mechanism of this paradoxical induction of c-fos by MK-801 is unclear; however, the pattern of induction appears to follow the distribution of the antagonist-preferring NMDA receptor site.     

Utility of in vitro proton magnetic resonance spectroscopy in aetiological characterisation of brain abscesses

Purpose: Brain abscesses often present an aetiological dilemma. Microscopy is insensitive and culture techniques are time consuming. Hence, a new rapid technique in vitro Proton Magnetic Resonance Spectroscopy (¹HMRS) was evaluated for its usefulness in the identification of aetiology of brain abscesses. Materials and Methods: A total of 39 pus specimens from brain abscesses were subjected to in vitro ¹HMRS. These pus specimens were also processed by conventional culture methods. The spectral patterns generated by in vitro ¹HMRS were further correlated with culture results. Results: Pus specimens which showed the presence of anaerobes on culture revealed the presence of multiplet at 0.9 ppm (100%), lactate-lipid at 1.3 ppm (100%), acetate at 1.92 ppm (100%) and succinate at 2.4 ppm (75%). Pus specimens that revealed the presence of facultative anaerobes on culture showed a pattern B, i.e., the presence of lactate-lipid at 1.3 ppm (100%), acetate at 1.92 ppm (88.88%) along with the multiplet at 0.9 ppm (100%). Pattern C was seen in aerobic infection which showed the presence of lactate-lipid at 1.3 ppm (100%) along with the multiplet at 0.9 ppm. Pus from two tuberculous abscesses showed the complete absence of multiplet at 0.9 ppm. Conclusions: We observed in this study that it was possible to differentiate bacterial and tuberculous brain abscesses using in vitro ¹HMRS. Further, it was also possible to distinguish between aerobic and anaerobic brain abscesses on the basis of spectral patterns. In vitro ¹HMRS of fungal and actinomycotic brain abscess are also presented for its unusual spectra.     

Localized proton NMR spectroscopy of experimental gliomas in rat brain in vivo.

Experimental brain tumors produced in rats (n = 10) by stereotactic implantation of cells from the F98 anaplastic glioma clone into the right caudate nucleus were studied in vivo using localized proton NMR and in vitro using high-resolution proton NMR, bioluminescent imaging of lactate, ATP and glucose distributions, and fluorescent imaging of regional pH. In vivo spectra from normal brain contralateral to the tumor regions showed resonances assignable to N-acetyl aspartate (NAA), creatines, choline-containing compounds, myo-inositol, glutamate and glucose in a pattern similar to those obtained from normal anaesthetized rats. In vivo tumor spectra were characterized by the almost complete absence of NAA, a substantial reduction of total creatine and glucose, and an increase of cholines. Based on the in vitro spectra the increase of the myo-inositol signal observed in vivo was mainly attributed to glycine. Histological examination as well as bioluminescent and fluorescent imaging indicated two stages of tumor development, i.e., solid vital tumors and tumors with necrosis. However, there was no consistent relationship between proton NMR observations and tumor development.