New rat model of spinal cord infarction with long-lasting functional disabilities generated by intraspinal injection of endothelin-1.

BACKGROUND: The current method for generating an animal model of spinal cord (SC) infarction is highly invasive and permits only short-term observation, typically limited to 28 days. OBJECTIVE: We aimed to establish a rat model characterised by long-term survival and enduring SC dysfunction by inducing selective ischaemic SC damage. METHODS: In 8-week-old male Wistar rats, a convection-enhanced delivery technique was applied to selectively deliver endothelin-1 (ET-1) to the anterior horn of the SC at the Th13 level, leading to SC infarction. The Basso, Beattie and Bresnahan (BBB) locomotor score was assessed for 56 days. The SC was examined by a laser tissue blood flowmeter, MRI, immunohistochemistry, triphenyl tetrazolium chloride (TTC) staining, Western blots and TUNEL staining. RESULTS: The puncture method was used to bilaterally inject 0.7 µL ET-1 (2.5 mg/mL) from the lateral SC into the anterior horns (40° angle, 1.5 mm depth) near the posterior root origin. Animals survived until day 56 and the BBB score was stably maintained (5.5±1.0 at day 14 and 6.2±1.0 at day 56). Rats with BBB scores ≤1 on day 1 showed stable scores of 5-6 after day 14 until day 56 while rats with BBB scores >1 on day 1 exhibited only minor dysfunction with BBB scores >12 after day 14. TTC staining, immunostaining and TUNEL staining revealed selective ischaemia and neuronal cell death in the anterior horn. T2-weighted MR images showed increasing signal intensity at the SC infarction site over time. Western blots revealed apoptosis and subsequent inflammation in SC tissue after ET-1 administration. CONCLUSIONS: Selective delivery of ET-1 into the SC allows for more precise localisation of the infarcted area at the targeted site and generates a rat SC infarction model with stable neurological dysfunction lasting 56 days.

Structural alterations in the amygdala and impaired social incentive learning in a mouse model of a genetic variant associated with neurodevelopmental disorders.

Copy number variants (CNVs) are robustly associated with psychiatric disorders and their dimensions and changes in brain structures and behavior. However, as CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how the genes in the 22q11.2 region individually contribute to structural alterations and associated mental illnesses and their dimensions. Our previous studies have identified Tbx1, a T-box family transcription factor encoded in 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes in congenic Tbx1 heterozygous mice. Our data show that the volumes of anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were reduced in Tbx1 heterozygous mice. Moreover, we examined the behavioral consequences of an altered volume of the amygdala. Tbx1 heterozygous mice were impaired for their ability to detect the incentive value of a social partner in a task that depends on the amygdala. Our findings identify the structural basis for a specific social dimension associated with loss-of-function variants of TBX1 and 22q11.2 CNV.

Structural alterations in the amygdala and impaired social incentive learning in a mouse model of a genetic variant associated with neurodevelopmental disorders.

Copy number variants (CNVs) are robustly associated with psychiatric disorders and their dimensions and changes in brain structures and behavior. However, as CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how the genes in the 22q11.2 region individually contribute to structural alterations and associated mental illnesses and their dimensions. Our previous studies have identified Tbx1, a T-box family transcription factor encoded in 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes in congenic Tbx1 heterozygous mice. Our data show that the volumes of anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were reduced in Tbx1 heterozygous mice. Moreover, we examined the behavioral consequences of an altered volume of the amygdala. Tbx1 heterozygous mice were impaired for their ability to detect the incentive value of a social partner in a task that depends on the amygdala. Our findings identify the structural basis for a specific social dimension associated with loss-of-function variants of TBX1 and 22q11.2 CNV.

Tbx1, a gene encoded in 22q11.2 copy number variant, is a link between alterations in fimbria myelination and cognitive speed in mice.

Copy number variants (CNVs) have provided a reliable entry point to identify the structural correlates of atypical cognitive development. Hemizygous deletion of human chromosome 22q11.2 is associated with impaired cognitive function; however, the mechanisms by which the CNVs contribute to cognitive deficits via diverse structural alterations in the brain remain unclear. This study aimed to determine the cellular basis of the link between alterations in brain structure and cognitive functions in mice with a heterozygous deletion of Tbx1, one of the 22q11.2-encoded genes. Ex vivo whole-brain diffusion-tensor imaging (DTI)-magnetic resonance imaging (MRI) in Tbx1 heterozygous mice indicated that the fimbria was the only region with significant myelin alteration. Electron microscopic and histological analyses showed that Tbx1 heterozygous mice exhibited an apparent absence of large myelinated axons and thicker myelin in medium axons in the fimbria, resulting in an overall decrease in myelin. The fimbria of Tbx1 heterozygous mice showed reduced mRNA levels of Ng2, a gene required to produce oligodendrocyte precursor cells. Moreover, postnatal progenitor cells derived from the subventricular zone, a source of oligodendrocytes in the fimbria, produced fewer oligodendrocytes in vitro. Behavioral analyses of these mice showed selectively slower acquisition of spatial memory and cognitive flexibility with no effects on their accuracy or sensory or motor capacities. Our findings provide a genetic and cellular basis for the compromised cognitive speed in patients with 22q11.2 hemizygous deletion.

Theanine, the Main Amino Acid in Tea, Prevents Stress-Induced Brain Atrophy by Modifying Early Stress Responses.

Chronic stress can impair the health of human brains. An important strategy that may prevent the accumulation of stress may be the consumption of functional foods. When senescence-accelerated mice prone 10 (SAMP10), a stress-sensitive strain, were loaded with stress using imposed male mouse territoriality, brain volume decreased. However, in mice that ingested theanine (6 mg/kg), the main amino acid in tea leaves, brain atrophy was suppressed, even under stress. On the other hand, brain atrophy was not clearly observed in a mouse strain that aged normally (Slc:ddY). The expression level of the transcription factor Npas4 (neuronal PAS domain protein 4), which regulates the formation and maintenance of inhibitory synapses in response to excitatory synaptic activity, decreased in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but increased in mice that ingested theanine. Lipocalin 2 (Lcn2), the expression of which increased in response to stress, was significantly high in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but not in mice that ingested theanine. These data suggest that Npas4 and Lcn2 are involved in the brain atrophy and stress vulnerability of SAMP10 mice, which are prevented by the consumption of theanine, causing changes in the expression of these genes.

Convection-enhanced delivery of a hydrophilic nitrosourea ameliorates deficits and suppresses tumor growth in experimental spinal cord glioma models.

BACKGROUND: Convection-enhanced delivery (CED) is a technique allowing local infusion of therapeutic agents into the central nervous system, circumventing the blood-brain or spinal cord barrier. OBJECTIVE: To evaluate the utility of nimustine hydrochloride (ACNU) CED in controlling tumor progression in an experimental spinal cord glioma model. METHODS: Toxicity studies were performed in 42 rats following the administration of 4 µl of ACNU CED into the mid-thoracic spinal cord at concentrations ranging from 0.1 to 10 mg/ml. Behavioral analyses and histological evaluations were performed to assess ACNU toxicity in the spinal cord. A survival study was performed in 32 rats following the implantation of 9 L cells into the T8 spinal cord. Seven days after the implantation, rats were assigned to four groups: ACNU CED (0.25 mg/ml; n = 8); ACNU intravenous (i.v.) (0.4 mg; n = 8); saline CED (n = 8); saline i.v. (n = 8). Hind limb movements were evaluated daily in all rats for 21 days. Tumor sizes were measured histologically. RESULTS: The maximum tolerated ACNU concentration was 0.25 mg/ml. Preservation of hind limb motor function and tumor growth suppression was observed in the ACNU CED (0.25 mg/ml) and ACNU i.v. groups. Antitumor effects were more prominent in the ACNU CED group especially in behavioral analyses (P < 0.05; log-rank test). CONCLUSIONS: ACNU CED had efficacy in controlling tumor growth and preserving neurological function in an experimental spinal cord tumor model. ACNU CED can be a viable treatment option for spinal cord high-grade glioma.

Sexual differentiation of the adolescent rat brain: A longitudinal voxel-based morphometry study.

The sexual differentiation of the rat brain during the adolescent period has been well documented in post-mortem histological studies. However, to further understand the morphological changes occurring in the entire brain, a noninvasive neuroimaging method allowing an unbiased, comprehensive, and longitudinal investigation of brain morphology should be used. In this study, we investigated the sexual differentiation of the rat brain during the adolescent period using longitudinal voxel-based morphometry (VBM) analysis. Male and female Wistar rats (n=12 of each) were scanned in a 7.0-T MRI scanner at five time points from 6 to 10 weeks of age. The T2-weighted MRI images were segmented using the rat brain tissue priors that have been published by our laboratory. At the global level, the results of the VBM analysis showed greater increases in total gray matter volume in the males during the adolescent period, although we did not find significant differences in total white matter volume. At the voxel level, we found significant increases in the regional gray matter volume of the occipital cortex, amygdala, hippocampal formation, and cerebellum. At the regional level, only the occipital cortex in the females exhibited decreases during the adolescent period. These results were, at least in part, consistent with those of previous longitudinal VBM studies in humans, thus providing translational evidence of the sexual differentiation of the developing brain between rodents and humans.

Regional Volume Decreases in the Brain of Pax6 Heterozygous Mutant Rats: MRI Deformation-Based Morphometry.

Pax6 is a transcription factor that pleiotropically regulates various developmental processes in the central nervous system. In a previous study, we revealed that Pax6 heterozygous mutant (rSey2/+) adult rats exhibit abnormalities in social interaction. However, the brain malformations underlying the behavioral abnormality are unknown. To elucidate the brain malformations in rSey2/+ rats, we morphometrically analyzed brains of rSey2/+ and wild type rats using small-animal magnetic resonance imaging (MRI). Sixty 10-week-old rats underwent brain MRI (29 rSey2/+ rats and 31 wild type rats). SPM8 software was used for image preprocessing and statistical image analysis. Normalized maps of the Jacobian determinant, a parameter for the expansion and/or contraction of brain regions, were obtained for each rat. rSey2/+ rats showed significant volume decreases in various brain regions including the neocortex, corpus callosum, olfactory structures, hippocampal formation, diencephalon, and midbrain compared to wild type rats. Among brain regions, the anterior commissure showed significant interaction between genotype and sex, indicating the effect of genotype difference on the anterior commissure volume was more robust in females than in males. The rSey2/+ rats exhibited decreased volume in various gray and white matter regions of the brain, which may contribute to manifestation of abnormal social behaviors.

Intraparenchymal ultrasound application and improved distribution of infusate with convection-enhanced delivery in rodent and nonhuman primate brain.

OBJECT Convection-enhanced delivery (CED) is an effective drug delivery method that delivers high concentrations of drugs directly into the targeted lesion beyond the blood-brain barrier. However, the drug distribution attained using CED has not satisfactorily covered the entire targeted lesion in tumors such as glioma. Recently, the efficacy of ultrasound assistance was reported for various drug delivery applications. The authors developed a new ultrasound-facilitated drug delivery (UFD) system that enables the application of ultrasound at the infusion site. The purpose of this study was to demonstrate the efficacy of the UFD system and to examine effective ultrasound profiles. METHODS The authors fabricated a steel bar-based device that generates ultrasound and enables infusion of the aqueous drug from one end of the bar. The volume of distribution (Vd) after infusion of 10 ml of 2% Evans blue dye (EBD) into rodent brain was tested with different frequencies and applied voltages: 252 kHz/30 V; 252 kHz/60 V; 524 kHz/13 V; 524 kHz/30 V; and 524 kHz/60 V. In addition, infusion of 5 mM gadopentetate dimeglumine (Gd-DTPA) was tested with 260 kHz/60 V, the distribution of which was evaluated using a 7-T MRI unit. In a nonhuman primate (Macaca fascicularis) study, 300 µl of 1 mM Gd-DTPA/EBD was infused. The final distribution was evaluated using MRI. Two-sample comparisons were made by Student t-test, and 1-way ANOVA was used for multiple comparisons. Significance was set at p < 0.05. RESULTS After infusion of 10 µl of EBD into the rat brain using the UFD system, the Vds of EBD in the UFD groups were significantly larger than those of the control group. When a frequency of 252 kHz was applied, the Vd of the group in which 60 V was applied was significantly larger than that of the group in which 30 V was used. When a frequency of 524 kHz was applied, the Vd tended to increase with application of a higher voltage; however, the differences were not significant (1-way ANOVA). The Vd of Gd-DTPA was also significantly larger in the UFD group than in the control group (p < 0.05, Student t-test). The volume of Gd-DTPA in the nonhuman primate used in this study was 1209.8 ± 193.6 mm(3). This volume was much larger than that achieved by conventional CED (568.6 ± 141.0 mm(3)). CONCLUSIONS The UFD system facilitated the distribution of EBD and Gd-DTPA more effectively than conventional CED. Lower frequency and higher applied voltage using resonance frequencies might be more effective to enlarge the Vd. The UFD system may provide a new treatment approach for CNS disorders.

Specific regions display altered grey matter volume in µ-opioid receptor knockout mice: MRI voxel-based morphometry.

BACKGROUND AND PURPOSE: µ Opioid receptor knockout (MOP-KO) mice display several behavioural differences from wild-type (WT) littermates including differential responses to nociceptive stimuli. Brain structural changes have been tied to behavioural alterations noted in transgenic mice with targeting of different genes. Hence, we assess the brain structure of MOP-KO mice. EXPERIMENTAL APPROACH: Magnetic resonance imaging (MRI) voxel-based morphometry (VBM) and histological methods were used to identify structural differences between extensively backcrossed MOP-KO mice and WT mice. KEY RESULTS: MOP-KO mice displayed robust increases in regional grey matter volume in olfactory bulb, several hypothalamic nuclei, periaqueductal grey (PAG) and several cerebellar areas, most confirmed by VBM analysis. The largest increases in grey matter volume were detected in the glomerular layer of the olfactory bulb, arcuate nucleus of hypothalamus, ventrolateral PAG (VLPAG) and cerebellar regions including paramedian and cerebellar lobules. Histological analyses confirm several of these results, with increased VLPAG cell numbers and increased thickness of the olfactory bulb granule cell layer and cerebellar molecular and granular cell layers. CONCLUSIONS AND IMPLICATIONS: MOP deletion causes previously undescribed structural changes in specific brain regions, but not in all regions with high MOP receptor densities (e.g. thalamus, nucleus accumbens) or that exhibit adult neurogenesis (e.g. hippocampus). Volume differences in hypothalamus and PAG may reflect behavioural changes including hyperalgesia. Although the precise relationship between volume change and MOP receptor deletion was not determined from this study alone, these findings suggest that levels of MOP receptor expression may influence a broader range of neural structure and function in humans than previously supposed. LINKED ARTICLES: This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

Prevention of cancer recurrence in tumor margins by stopping microcirculation in the tumor and tumor-host interface.

Combretastatins interrupt blood flow of solid tumor vascular networks and lead to necrosis by blocking nutrients. However, tumors recover from tumor blood flow interruption-induced damage and develop viable rims. To investigate why cancer recurs and its prevention, we used a combretastatin derivative, Cderiv (=AC7700), and analyzed changes in tumor-host interface (T-HI) vessels, which were closest to cancer cells in the tumor margin after tumor vessel disruption, and the microenvironment surrounding them. Treatment with Cderiv (10 mg/kg) interrupted tumor blood flow in all regions of LY80 (a variant of Yoshida sarcoma) tumor, but not T-HI vessel blood flow. The same Cderiv dose given 72 h after 5 Gy irradiation stopped T-HI vessel blood flow and prevented cancer recurrence. Treatment in the reverse order, however, did not affect T-HI vessel blood flow. The greatest difference between the two treatments was the occurrence of gradual T-HI edema with the former. Severe T-HI edema compressed T-HI blood vessels, so that circulation stopped. Thus, the distance between a tumor margin and its nearest functioning host vessel became much larger, and the tumor marginal region became a microenvironment that lacked a nutritional supply. Cancer cells in tumor margins received nutrients through two circulation routes: tumor vessels and T-HI vessels. Our starvation methods, which involved treatment with Cderiv 72 h after 5 Gy irradiation, blocked both circulation routes and may have great potential as a clinical strategy to prevent cancer recurrence.

Regional gray matter volume increases following 7days of voluntary wheel running exercise: a longitudinal VBM study in rats.

The effects of physical exercise on brain morphology in rodents have been well documented in histological studies. However, to further understand when and where morphological changes occur in the whole brain, a noninvasive neuroimaging method allowing an unbiased, comprehensive, and longitudinal investigation of brain morphology should be used. In this study, we investigated the effects of 7days of voluntary wheel running exercise on regional gray matter volume (rGMV) using longitudinal voxel-based morphometry (VBM) in rats. Eighteen pairs of adult male naïve Wistar rats were randomized to the exercise or control condition (one rat for each condition from each pair). Each rat was scanned in a 7.0-T MRI scanner at three time points: before exercise, after 7days of exercise, and after 7days of follow-up. The T2-weighted MRI images were segmented using the rat brain tissue priors that were recently published by our laboratory, and the intra- and inter-subject template creation steps were followed. Longitudinal VBM analysis revealed significant increases in rGMV in the motor, somatosensory, association, and visual cortices in the exercise group. Among these brain regions, rGMV changes in the motor cortex were positively correlated with the total distance that was run during the 7days of exercise. In addition, the effects of 7days of exercise on rGMV persisted after 7days of follow-up. These results support the utility of a longitudinal VBM study in rats and provide new insights into experience-dependent structural brain plasticity in naïve adult animals.

Pitfalls in the dipolar model for the neocortical EEG sources.

For about six decades, primary current sources of the electroencephalogram (EEG) have been assumed dipolar in nature. In this study, we used electrophysiological recordings from anesthetized Wistar rats undergoing repeated whisker deflections to revise the biophysical foundations of the EEG dipolar model. In a first experiment, we performed three-dimensional recordings of extracellular potentials from a large portion of the barrel field to estimate intracortical multipolar moments generated either by single spiking neurons (i.e., pyramidal cells, PC; spiny stellate cells, SS) or by populations of them while experiencing synchronized postsynaptic potentials. As expected, backpropagating spikes along PC dendrites caused dipolar field components larger in the direction perpendicular to the cortical surface (49.7 ± 22.0 nA·mm). In agreement with the fact that SS cells have "close-field" configurations, their dipolar moment at any direction was negligible. Surprisingly, monopolar field components were detectable both at the level of single units (i.e., -11.7 ± 3.4 nA for PC) and at the mesoscopic level of mixed neuronal populations receiving extended synaptic inputs within either a cortical column (-0.44 ± 0.20 µA) or a 2.5-m(3)-voxel volume (-3.32 ± 1.20 µA). To evaluate the relationship between the macroscopically defined EEG equivalent dipole and the mesoscopic intracortical multipolar moments, we performed concurrent recordings of high-resolution skull EEG and laminar local field potentials. From this second experiment, we estimated the time-varying EEG equivalent dipole for the entire barrel field using either a multiple dipole fitting or a distributed type of EEG inverse solution. We demonstrated that mesoscopic multipolar components are altogether absorbed by any equivalent dipole in both types of inverse solutions. We conclude that the primary current sources of the EEG in the neocortex of rodents are not precisely represented by a single equivalent dipole and that the existence of monopolar components must be also considered at the mesoscopic level.

Large-scale heterogeneous representation of sound attributes in rat primary auditory cortex: from unit activity to population dynamics.

Recent evidence indicates the existence of pyramidal cells (PCs) and interneurons with nontrivial tuning characteristics for sound attributes in the primary auditory cortex (A1) of mammals. These neurons are functionally distributed into layers and sparsely organized at a small scale. However, their topological locations at a large scale in A1 have not yet been investigated. Furthermore, these neurons are usually classified from fine maps of attribute-dependent spiking activity, and not much attention is paid to population postsynaptic potentials related to their activity. We used extracellular recordings obtained from multiple sites in A1 of adult rats to determine neuronal codifiers for sound attributes defined by coarse representations of the population dose-response curves. We demonstrated that these codifiers, majorly involving PCs, are heterogeneously distributed along A1. Spiking activity in these neurons during stimulation was correlated to ß (12-25 Hz) and low γ (25-70 Hz) postsynaptic oscillations in the infragranular layer, whereas in the supragranular layer, better correlations were found with high γ (70-170 Hz) oscillations. The time-frequency analysis of the postsynaptic potentials showed a transient broadband power increase in all layers after the stimulus onset that was followed by a sustained high γ oscillation in the supragranular layer, fluctuations in the laminar content of the low-frequency oscillations, and a global attenuation in the low-frequency powers after the stimulus offset that happened together with a long-lasting strengthening of the ß oscillations. We concluded that, for rats, sounds are codified in A1 by segregated networks of specialized PCs whose postsynaptic activity impinges on the emergence of sparse/dense spiking patterns.

An in vivo MRI Template Set for Morphometry, Tissue Segmentation, and fMRI Localization in Rats.

Over the last decade, several papers have focused on the construction of highly detailed mouse high field magnetic resonance image (MRI) templates via non-linear registration to unbiased reference spaces, allowing for a variety of neuroimaging applications such as robust morphometric analyses. However, work in rats has only provided medium field MRI averages based on linear registration to biased spaces with the sole purpose of approximate functional MRI (fMRI) localization. This precludes any morphometric analysis in spite of the need of exploring in detail the neuroanatomical substrates of diseases in a recent advent of rat models. In this paper we present a new in vivo rat T2 MRI template set, comprising average images of both intensity and shape, obtained via non-linear registration. Also, unlike previous rat template sets, we include white and gray matter probabilistic segmentations, expanding its use to those applications demanding prior-based tissue segmentation, e.g., statistical parametric mapping (SPM) voxel-based morphometry. We also provide a preliminary digitalization of latest Paxinos and Watson atlas for anatomical and functional interpretations within the cerebral cortex. We confirmed that, like with previous templates, forepaw and hindpaw fMRI activations can be correctly localized in the expected atlas structure. To exemplify the use of our new MRI template set, were reported the volumes of brain tissues and cortical structures and probed their relationships with ontogenetic development. Other in vivo applications in the near future can be tensor-, deformation-, or voxel-based morphometry, morphological connectivity, and diffusion tensor-based anatomical connectivity. Our template set, freely available through the SPM extension website, could be an important tool for future longitudinal and/or functional extensive preclinical studies.

A case of adult-onset type II citrullinemia with comorbid epilepsy even after liver transplantation.

The current study using single case voxel-based morphometry (VBM) of magnetic resonance imaging (MRI) and ¹H-MR-spectroscopy (¹H-MRS) explores the neural background of unexplained seizure attacks and electroencephalography (EEG) abnormalities persisting even after liver transplantation in a patient with adult-onset type II citrullinemia (CTLN2). Although the MRI had shown no gross abnormality, the VBM revealed significantly smaller-than-normal regional volume in the left hippocampus of the patient as compared with 111 age-matched controls. ¹H-MRS further indicated reduction of all metabolite concentrations in the left hippocampus compared with those in the right homolog region, with the single exception of elevated glutamate concentration. These results are similar to those of patients with mesial temporal lobe epilepsy (TLE), although CTLN2-complicated mesial TLE has rarely been reported. In contrast to TLE, periictal asterixis and interictal slow activities on EEG support another possibility that the patient might have slight metabolic encephalopathy even after the liver transplantation.

Specific metabolites in the medial prefrontal cortex are associated with the neurocognitive deficits in schizophrenia: a preliminary study.

We measured brain metabolites in the medial prefrontal cortex of 19 schizophrenic patients and 18 healthy controls by 3 T proton magnetic resonance spectroscopy ((1)H MRS), and examined the relationship between prefrontal cortex-related neurocognitive functions and brain metabolites in the medial prefrontal cortex. The patients with schizophrenia exhibited deficits on the verbal fluency, Wisconsin card sorting test (WCST), trail making test, Stroop test and digit span distraction test (DSDT), but not on the Iowa gambling test. The patients showed statistical significant changes in the ratio of glutamine/glutamate, the ratio of N-acetyl-l-aspartate (NAA)/glycerophosphorylcholine plus phosphorylcholine (GPC+PC) and the levels of taurine in the medial prefrontal cortex compared with normal controls. Furthermore, we found significant correlations of the ratio of glutamine/glutamate with WCST and DSDT scores, the ratio of NAA/(GPC+PC) with verbal fluency and WCST scores, and the levels of taurine with scores on the Stroop test and Trail making test A among the participants. The ratios of NAA/(GPC+PC) and (GPC+PC)/(Cr+PCr) had significant relationships with the duration of untreated psychosis of the schizophrenic patients. The glutamine/glutamate ratio and levels of taurine were significantly related to the duration of illness of the patients. These data suggest that specific metabolites of the medial prefrontal cortex are associated with the neurocognitive deficits in schizophrenia.

Monitoring of liver glycogen synthesis in diabetic patients using carbon-13 MR spectroscopy.

To investigate the relationship between liver glucose, glycogen, and plasma glucose in diabetic patients, in vivo liver carbon-13 magnetic resonance spectroscopy ((13)C MRS) with a clinical 3.0T MR system was performed. Subjects were healthy male volunteers (n=5) and male type-2 diabetic patients (n=5). Pre- and during oral glucose tolerance tests (OGTT), (13)C MR spectra without proton decoupling were acquired in a monitoring period of over 6h, and in total seven spectra were obtained from each subject. For OGTT, 75g of glucose, including 5g of [1-(13)C]glucose, was administered. The MR signals of liver [1-(13)C]glucose and glycogen were detected and their time-course changes were assessed in comparison with the plasma data obtained at screening. The correlations between the fasting plasma glucose level and liver glycogen/glucose rate (Spearman: rho=-0.68, p<0.05, n=10) and the fasting plasma glucose level and liver glycogen peak/fasting rate (Spearman: rho=-0.67, p<0.05, n=10) indicated that (13)C MRS can perform noninvasive measurement of glycogen storage/degradation ability in the liver individually and can assist in tailor-made therapy for diabetes. In conclusion, (13)C MRS has a potential to become a powerful tool in diagnosing diabetes multilaterally.

A multi-compartmental SE-BOLD interpretation for stimulus-related signal changes in diffusion-weighted functional MRI.

A new interpretation is proposed for stimulus-induced signal changes in diffusion-weighted functional MRI. T(2)-weighted spin-echo echo-planar images were acquired at different diffusion-weightings while visual stimulation was presented to human volunteers. The amplitudes of the positive stimulus-correlated response and post-stimulus undershoot (PSU) in the functional time-courses were found to follow different trends as a function of b-value. Data were analysed using a three-compartment signal model, with one compartment being purely vascular and the other two dominated by fast- and slow-diffusing molecules in the brain tissue. The diffusion coefficients of the tissue were assumed to be constant throughout the experiments. It is shown that the stimulus-induced signal changes can be decomposed into independent contributions originating from each of the three compartments. After decomposition, the fast-diffusion phase displays a substantial PSU, while the slow-diffusion phase demonstrates a highly reproducible and stimulus-correlated time-course with minimal undershoot. The decomposed responses are interpreted in terms of the spin-echo blood oxygenation level dependent (SE-BOLD) effect, and it is proposed that the signal produced by fast- and slow-diffusing molecules reflect a sensitivity to susceptibility changes in arteriole/venule- and capillary-sized vessels, respectively. This interpretation suggests that diffusion-weighted SE-BOLD imaging may provide subtle information about the haemodynamic and neuronal responses.

Analgesic effect of milnacipran is associated with c-Fos expression in the anterior cingulate cortex in the rat neuropathic pain model.

The objective of the present study was to examine whether milnacipran, a serotonin-noradrenaline reuptake inhibitor, has an analgesic effect in rats with neuropathic pain. In addition, the c-Fos expression was investigated in the supraspinal sites of the brain and in the spinal dorsal horn in association with the nociceptive processing in rats with neuropathic pain produced by chronic constriction injury (CCI) in the sciatic nerve. In the CCI-induced neuropathic rats, behavioral testing for determining the change in the withdrawal threshold to mechanical stimulation and immunohistochemical detection of c-Fos were both performed. The anti-allodynic effect derived from milnacipran gradually increased over the observation period, indicating that the delayed-onset analgesia might be elicited by the continuous administration of milnacipran. The increased level of c-Fos expression in the anterior cingulate cortex (ACC) induced by noxious mechanical stimulation was significantly inhibited by the continuous administration of milnacipran, indicating that milnacipran might cause a functional modification in the nociceptive processing in the ACC.