Mirtazapine modulates Glutamate and GABA levels in the animal model of maternal depression. MRI and 1H MRS study in female rats.

We aimed to determine, using in vivo magnetic resonance, whether maternal depression induced by chronic unpredictable stress (CUS) in the pre-gestational period in female rats would be evidenced by structural or neurometabolic changes in the hippocampal region of the brain. At the same time, appropriate behavioral tests were also administered after a relatively long two-month period of a stress paradigm. The objective of the study was not only to study an animal model of CUS using magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (1H MRS) focused on the hippocampus, but also to use this technique to verify the effectiveness of mirtazapine antidepressant treatment. In the group with CUS, we found a significant decrease in the relative concentration of γ-aminobutyric acid (GABA/tCr) and glutamate+glutamine (Glx/tCr) compared to the control group, while we did not observe any statistically significant change in hippocampal volumes. Moreover, the forced swim test revealed an increase in depression-like behavior. The most important finding was the return of GABA/tCr and Glx/tCr levels to control levels during mirtazapine treatment; however, behavioral tests did not demonstrate any effects from mirtazapine treatment. In vivo1H MRS confirmed mirtazapine modulation of CUS in an animal model more robustly than behavioral tests.

Huperzine aggravated neurochemical and volumetric changes induced by D-galactose in the model of neurodegeneration in rats.

The multimodal MRI and 1H MRS study was designed to provide a structural and neurochemical view of D-galactose induced rat brain degeneration and its treatment with huperzine A. The volume changes were captured using MRI focused on the hippocampal region and a neurochemical profile was obtained from the same area using in vivo localized 1H MRS, which was compared with in vitro1H MRS hippocampal spectra at the high field after the animals were culled. At the four week point, we observed a small decrease in N-acetylaspartate/creatine (NAA/tCr), myo-inositol/creatine (mIns/tCr) and glutamine/creatine (Gln/tCr) in the group in which neurodegeneration was induced. At the eight week point, we found only slight but statistically significant decreases in NAA/tCr, mIns/tCr and glutamate/creatine (Glu/tCr) in this group in vivo. However, in the treated group, the decrease in NAA/tCr and Glu/tCr was much more pronounced compared to the D-gal group. In vitro1H MRS analysis from rat hippocampal samples showed very similar changes in metabolites, which were also much more pronounced in the treated group. Neurodegeneration was also confirmed by a significant decrease in γ-aminobutyrate/creatine (GABA/tCr) observed only in the treated group, but not in the D-gal group. MRI image data and subsequent volumetric quantification showed mild hippocampal degeneration at the four week point in D-gal group. At the eight week point, we observed a decrease in hippocampal volume in both experimental groups, with a more pronounced decrease in the huperzine-treated group. In conclusion, in our experimental design huperzine A treatment worsened the neurodegeneration of the rat brain, which was supported by all of the used MRI and 1H MRS methods.

D-galactose-induced aging in rats - The effect of metformin on bioenergetics of brain, skeletal muscle and liver.

Chronic D-galactose administration induces accelerated aging in rodents. The aim of the study was to find by in vivo31P MRS suitable markers of early stages of brain degeneration on this metabolic model in rats. Additionally, we studied the therapeutic effect of antidiabetic drug metformin. The study has been extended by in vitro determination of mitochondrial function in brain, skeletal muscle and liver mitochondria, oxidative stress parameter thiobarbituric acid reactive substances (TBARS), and lipophilic antioxidants levels. In vivo31P MRS revealed lower intracellular pH (pHi) and lower inorganic phosphate to ATP ratio (Pi/ATP), with higher index of oxidative phosphorylation - phosphocreatine (PCr) to Pi ratio - in brain of rats chronically administered with D-galactose. The function of brain mitochondria was not affected. Administration of metformin diminished changes in brain pHi and plasma TBARS. The function of skeletal muscle mitochondria and their coenzyme Q (CoQ) content were considerably reduced after D-galactose administration. Metformin administered simultaneously with D-galactose did not prevent these changes. The results of in vivo31P MRS revealed evidence of early stage of neurodegeneration that may indicate pre-inflammation. Our data show different susceptibility of brain, skeletal muscle, and liver to the chronic exposure to D-galactose and metformin. The D-galactose model presented in the literature as a model for "age-related dementia" had much more devastating effects on skeletal muscle than on the brain.

Imaging of striatal injury in a songbird brain.

Neurological insults affect both, brain structure and behavior. The injury-induced brain plasticity and associated changes in behavior are difficult to study using classical histological methods. The magnetic resonance imaging (MRI), however, enables repeated inspection of the brain in the same individual. Here we took advantage of the songbird model with discrete brain circuitry controlling song learning and production and assessed if a conventional MRI is suitable to detect even relatively small brain changes. Our aim was to monitor injury and the following regeneration in the striatal vocal nucleus Area X that controls vocal learning in juveniles and affects song in adult songbird zebra finch (Taeniopygia guttata). The regeneration process was detected using T2-weighted images and validated by immunohistochemical (IHC) staining up to 6 months after the injury. Despite the small volume of the zebra finch brain, a satisfactory signal-to-noise ratio was achieved with reasonably short measurement times. No significant difference was found between the measurements of the lesion size obtained by MRI and IHC staining. Our data show that the non-invasive MRI technique can reliably measure and quantify the regeneration process even in a relatively small part of the brain and that the avian striatum progressively regenerates after its neurotoxic injury.

Neuronal marker recovery after Simvastatin treatment in dementia in the rat brain: in vivo magnetic resonance study.

The aim of study was to search for new biomarkers with a magnetic resonance technique to identify the early stages of dementia, induced by D-galactose, and evaluate Simvastatin therapy. Localized proton magnetic resonance spectroscopy measurements showed a significant decrease in the concentration of N-acetylaspartate+N-acetylaspartylglutamate and myo-inositol in the D-galactose group compared to the control group, and, conversely, an increase of N-acetylaspartate+N-acetylaspartylglutamate in the D-galactose/Simvastatin group. Using a saturation transfer experiment, with phosphorus magnetic resonance spectroscopy, we observed a significant elevation of the forward rate constant of the creatine kinase reaction in the brains of the D-galactose group compared to controls, and subsequently, a significant reduction of this reaction in the D-galactose/Simvastatin group. Spatial learning and memory were evaluated using the modified Morris water maze test. The dynamics of the learning process represented by the learning index revealed a significant reduction in learning in the D-galactose group, but the deficits as a consequence of the D-galactose effects were recovered in the D-galactose/Simvastatin group, in which the learning dynamics resembled those of the control group. By determining the thiobarbituric acid reactive substances and total coenzyme Q9 in plasma, we have shown that long-term administration of D-galactose created conditions for oxidative stress, and that the administration of Simvastatin decreased oxidative stress in plasma. Volumetry analyses from the hippocampal area show a reduction in the segmented area in the D-galactose group, compared with the control group, and an enlarged area in the hippocampus in the d-galactose/Simvastatin group.

Pathophysiological rat model of vascular dementia: magnetic resonance spectroscopy, microimaging and behavioral study.

Chronic cerebral hypoperfusion and aging can be related to vascular dementia manifested by the decline in cognitive abilities and memory impairment. The identification of specific biomarkers of vascular disorder in early stages is important for the development of neuroprotective agents. In the present study, a three-vessel occlusion (3-VO) rat model of vascular dementia in the middle-aged rat brain was used to investigate the effect of global cerebral hypoperfusion. A multimodal study was performed using magnetic resonance spectroscopy, MR-microimaging, histology and behavioral tests. Our measurements showed a signal alteration in T2-weighted MR images, the elevation of T2 relaxation times and histologically proven neural cell death in the hippocampal area, as well as mild changes in concentration of proton and phosphorus metabolites. These changes were accompanied by mild behavioral alterations in the open field and slightly decreased habituation. The analysis of the effects of vascular pathology on cognitive functions and neurodegeneration can contribute to the development of new treatment strategies for early stages of neurodegeneration.

In vivo and in vitro assessment of brain bioenergetics in aging rats.

Brain energy disorders can be present in aged men and animals. To this respect, the mitochondrial and free radical theory of aging postulates that age-associated brain energy disorders are caused by an imbalance between pro- and anti-oxidants that can result in oxidative stress. Our study was designed to investigate brain energy metabolism and the activity of endogenous antioxidants during their lifespan in male Wistar rats. In vivo brain bioenergetics were measured using ³¹P nuclear magnetic resonance (NMR) spectroscopy and in vitro by polarographic analysis of mitochondrial oxidative phosphorylation. When compared to the young controls, a significant decrease of age-dependent mitochondrial respiration and adenosine-3-phosphate (ATP) production measured in vitro correlated with significant reduction of forward creatine kinase reaction (kfor) and with an increase in phosphocreatine (PCr)/ATP, PCr/Pi and PME/ATP ratio measured in vivo. The levels of enzymatic antioxidants catalase, GPx and GST significantly decreased in the brain tissue as well as in the peripheral blood of aged rats. We suppose that mitochondrial dysfunction and oxidative inactivation of endogenous enzymes may participate in age-related disorders of brain energy metabolism.

Effect of coenzyme Q10 and vitamin E on brain energy metabolism in the animal model of Huntington's disease.

The neuropathological and clinical symptoms of Huntington's disease (HD) can be simulated in animal model with systemic administration of 3-nitropropionic acid (3-NP). Energy defects in HD could be ameliorated by administration of coenzyme Q(10) (CoQ(10)), creatine, or nicotinamid. We studied the activity of creatine kinase (CK) and the function of mitochondrial respiratory chain in the brain of aged rats administered with 3-NP with and without previous application of antioxidants CoQ(10)+vitamin E. We used dynamic and steady-state methods of in vivo phosphorus magnetic resonance spectroscopy ((31)P MRS) for determination of the pseudo-first order rate constant (k(for)) of the forward CK reaction, the phosphocreatine (PCr) to adenosinetriphosphate (ATP) ratio, intracellular pH(i) and Mg(i)(2+) content in the brain. The respiratory chain function of isolated mitochondria was assessed polarographically; the concentration of CoQ(10) and alpha-tocopherol by HPLC. We found significant elevation of k(for) in brains of 3-NP rats, reflecting increased rate of CK reaction in cytosol. The function of respiratory chain in the presence of succinate was severely diminished. The activity of cytochromeoxidase and mitochondrial concentration of CoQ(10) was unaltered; tissue content of CoQ(10) was decreased in 3-NP rats. Antioxidants CoQ(10)+vitamin E prevented increase of k(for) and the decrease of CoQ(10) content in brain tissue, but were ineffective to prevent the decline of respiratory chain function. We suppose that increased activity of CK system could be compensatory to decreased mitochondrial ATP production, and CoQ(10)+vitamin E could prevent the increase of k(for) after 3-NP treatment likely by activity of CoQ(10) outside the mitochondria. Results of our experiments contributed to elucidation of mechanism of beneficial effect of CoQ(10) administration in HD and showed that the rate constant of CK is a sensitive indicator of brain energy disorder reflecting therapeutic effect of drugs that could be used as a new in vivo biomarker of neurodegenerative diseases.

Study of the oxidative stress in a rat model of chronic brain hypoperfusion.

A multiple analysis of the cerebral oxidative stress was performed on a physiological model of dementia accomplished by three-vessel occlusion in aged rats. The forward rate constant of creatine kinase, k(for), was studied by saturation transfer (31)P magnetic resonance spectroscopy in adult and aged rat brain during chronic hypoperfusion. In addition, free radicals in aging rat brain homogenates before and/or after occlusion were investigated by spin-trapping electron paramagnetic resonance spectroscopy (EPR). Finally, biochemical measurements of oxidative phosphorylation parameters in the above physiological model were performed. The significant reduction of k(for) in rat brain compared to controls 2 and 10 weeks after occlusion indicates a disorder in brain energy metabolism. This result is consistent with the decrease of the coefficient of oxidative phosphorylation (ADP:O), and the oxidative phosphorylation rate measured in vitro on brain mitochondria. The EPR study showed a significant increase of the ascorbyl free radical concentration in this animal model. Application of alpha-phenyl-N-tert-butylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin traps revealed formation of highly reactive hydroxyl radical (.OH) trapped in DMSO as the .CH(3) adduct. It was concluded that the ascorbate as a major antioxidant in brain seems to be useful in monitoring chronic cerebral hypoperfusion.

New magnetic resonance spectroscopy biomarker for monitoring neurodegenerative diseases: animal models.

Creatine kinase (CK) plays a central role in energy transfer in cells with high-energy demands, and the enzyme is rather susceptible to oxidative inactivation. The aim of the present study was to investigate whether the rate constant of forward CK reaction (k(for)) is a suitable indicator of alterations in cerebral energy metabolism. We monitored k(for) in the rat brain non-invasively by in vivo phosphorus ((31)P) magnetic resonance spectroscopy (MRS). To alter energy metabolism, we applied following experimental models: Huntington's disease, diabetes mellitus, chronic alcohol intoxication and chronic cerebral hypoperfusion (vascular dementia model). Results of our (31)P MRS experiment confirm importance of creatine kinase/phosphocreatinine (CK/PCr) system in the regulation of brain energy metabolism in vivo because a kinetic parameter k(for) was significantly changed in all above animal models that simulate neurodegenerative diseases or commonly during oxidative stress. Using this method we distinguished vascular dementia (VD) and Huntington disease (HD), because in VD model a kinetic parameter k(for) decreased and in the case HD increased. Considering the importance of CK for the maintenance of energy homeostasis in the brain, it is conceivable that an alteration of this enzyme activity in the brain may be one of the mechanisms by which various neurodegenerative diseases might be monitored just by means saturation transfer method (31)P MRS.