A polymer/enzyme composite biosensor for monitoring neurochemical glutamate was performance optimised in vitro for sensitivity, selectivity and stability. This first generation Pt/glutamate ...oxidase-based sensor displayed appropriate sensitivity (90.4 ± 2.0 nA cm−2 μM−1). It also has ideal stability/biocompatibility with no significant decrease in response observed for repeated calibrations, exposure to electron beam sterilisation, or following storage at 4 °C either dry (28 days) or in ex-vivo rodent brain tissue (14 days). Potential non-glutamate contributing signals, generated by extracellular levels of the principal endogenous electroactive interferents, were typically <5% of the basal (10 μM) glutamate response. Changes in molecular oxygen (the natural enzyme mediator) over the normal brain tissue range of 40–80 μM had minimal effect on the glutamate signal for concentrations of 10 and 100 μM (Mean KMO2 = 1.86 ± 0.74 μM, O290% = ca. 15 μM). Additionally, a low μM calculated limit of detection (0.44 ± 0.05) and rapid response time (ca. 1.67 ± 0.06 s), combined with no effect of pH and temperature changes over physiologically relevant ranges (7.2–7.6 and 34–40 °C respectively), collectively suggest that this composite biosensor should reliably detect l-glutamate when used for neurochemical monitoring. Preliminary experiments involving implantation in the striatum of freely moving rats demonstrated stable recording over several weeks, and reliable detection of physiological changes in glutamate in response to behavioural/neuronal activation (locomotor activity and restraint stress).
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•In vitro performance optimisation of a composite biosensor for neurochemical glutamate.•Reduced manufacturing time, low μM limit of detection and rapid response time.•No effect of interferent, pH and temperature changes over physiologically relevant ranges.•No loss of sensitivity following sterilisation and stable recording over several weeks in vivo.•Reliable detection of physiological changes in response to behavioural/neuronal activation.
•GABAAα1, GABAB1, and mGlu2 receptors expression levels in the primary visual cortex increased with age during the first two weeks of postnatal period in male neonates born to normal, diabetic and ...insulin-treated diabetic mothers.•The expression of all three receptors was significantly decreased in all layers of the primary visual cortex at all three postnatal days (Po, P7, and P14) in male neonates born to diabetic rats.•Insulin treatment had a modulatory effect on receptor expression.
This study examines the impact of maternal diabetes on the expression of GABAB1, GABAAα1, and mGlu2 receptors in the primary visual cortex layers of male rat newborns.
Main Methods: In diabetic group (Dia), diabetes was induced in adult female rats using an intraperitoneal dose of Streptozotocin (STZ) 65 (mg/kg). Diabetes was managed by daily subcutaneous injection of NPH insulin in insulin-treated diabetic group (Ins). Control group (Con) received normal saline intraperitoneally rather than STZ. Male offspring born to each group of female rats were euthanized via CO2 inhalation at P0, P7, and P14 days after delivery and the expression of GABAB1, GABAAα1, and mGlu2 receptors in their primary visual cortex was determined using immunohistochemistry (IHC).
Key Findings: The expression of GABAB1, GABAAα1, and mGlu2 receptors increased gradually with age in the male offspring born to Con group while the highest expression was detected in layer IV of the primary visual cortex. In Dia group newborns, the expression of these receptors was significantly reduced in all layers of the primary visual cortex at every three days. Insulin treatment in diabetic mothers restored the expression of these receptors to normal levels in their newborns.
The study indicates that diabetes reduces the expression of GABAB1, GABAAα1, and mGlu2 receptors in the primary visual cortex of male offspring born to diabetic rats at P0, P7, and P14. However, insulin treatment can counteract these effects.
•Finite element methods provide an exceptional tool to model current dynamics in the sleeping brain, to better understand the physiological mechanisms of the transcranial electrical stimulation. It ...also fosters the refinement of techniques, and the potential replacement of animals.•The stimulation of the current frequency is crucial in some studies in the field of neuroscience and concretely in sleep research; however, this parameter is hardly accounted in computational models using FEM to assess the behavior of the electrical current in the brain.•Stimulation frequency has comparative less impact on electric field than electrode configurations.•Subcranial screw anodes affect deeper brain areas and display higher current density and electric field across stimulation frequencies. Nevertheless, both modeled electrode setups (screw and plate) impose electric current to a wide portion of the brain.•The use of FEM to model and simulate current behavior in the brain is very relevant for neuroscience and concretely for sleep research. It not only allows for sophistication of the mechanistic explanations of the effect of electrical stimulation in the brain.
A realistic rat brain model was used to simulate current density and electric field distributions under frequencies characteristic of sleeping states (0.8, 5, and 12 Hz). Two anode-electrode setups were simulated: plate vs. screws-anode, both with a cephalic cathode. Our simulations showed that these frequencies have limited impact on electric field and current density; however, the highest frequency evidenced higher values for both variables. The type of electrode setup had a greater effect on current distribution and induced fields. In that sense, the screws setup resulted in higher values of the modeled variables. The numeric results obtained are within the range of available data for rodent models using the finite elements method. These modeled effects should be analyzed regarding anatomical consequences (depth of penetration of the currents) and purpose of the experiment (i.e., entrainment of brain oscillations) in the context of sleep research.
In this study, a novel of magnetic molecularly imprinted polymers (Fe3O4/GO/DMIPs) with multi-targets recognizing function were prepared by surface molecular imprinting technique adopting ...isoprenaline as the dummy-template molecule and graphene oxide (GO) as the carrier. The morphology, structures and magnetic properties of nanosorbents were characterized and assessed in detail and the results indicated that the 3D recognition cavities and matching functional groups with catecholamine neurotransmitters (CNs) were successfully fabricated on Fe3O4/GO surface. Moreover, the kinetic, isothermal and selective adsorption experiments were conducted to further reveal the adsorption behavior of adsorbent toward CNs and the results showed that the Fe3O4/GO/DMIPs possessed high adsorption capacity, rapid binding rate and excellent selectivity for CNs. On this basis, the Fe3O4/GO/DMIPs were further applied as adsorbent of magnetic solid-phase extraction (MSPE) for selective recognition and separation of CNs (dopamine, epinephrine, norepinephrine) followed by UPLC-MS/MS detection. The crucial parameters affecting the extraction efficiency were systematically optimized by Box-Behnken statistical design. Under the optimum conditions, satisfactory linearity (r > 0.99) was obtained with the lower limit of quantification from 0.53 to 1.93 ng mL−1. The accuracy (RE) ranged from −7.6% to 6.4% and the intra- and inter-day precisions were not more than 8.7% and 10.2%, respectively. Hence, the strategy proposed in this study might be used for high selectivity recognition and determination of CNs in complex biological matrices, which would provide a basis and reference for its application in the fields of separation and clinical monitoring.
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•The 3D recognition cavities and matching functional groups with CNs were fabricated on Fe3O4/GO surface at first time.•The prepared Fe3O4/GO/DMIPs can be employed to simultaneous selective recognition of three CNs.•The Fe3O4/GO/DMIPs not only have high selectivity for CNs but can be quickly separated from solutions with a magnet.•A simple and reliable strategy for MSPE-UPLC-MS/MS was established for analysis of CNs in rat brain tissues.
Abstract
Network analyses of structural connectivity in the brain have highlighted a set of highly connected hubs that are densely interconnected, forming a "rich-club" substrate in diverse species. ...Here, we demonstrate the existence of rich-club organization in functional brain networks of rats. Densely interconnected rich-club regions are found to be distributed in multiple brain modules, with the majority located within the putative default mode network. Rich-club members exhibit high wiring cost (as measured by connection distance) and high metabolic running cost (as surrogated by cerebral blood flow), which may have evolved to achieve high network communications to support efficient brain functions. Furthermore, by adopting a forepaw electrical stimulation paradigm, we find that the rich-club organization of the rat functional network remains almost the same as in the resting state, whereas path motif analysis reveals significant differences, suggesting the rat brain reorganizes its topological routes by increasing locally oriented shortcuts but reducing rich-club member-involved paths to conserve metabolic running cost during unimodal stimulation. Together, our results suggest that the neuronal system is organized and dynamically operated in an economic way to balance between cost minimization and topological/functional efficiency.
The aim of the current study was to establish a controlled and reproducible model to study metabolic changes during oxygen–glucose deprivation (OGD) in rat brain using a nuclear magnetic resonance ...(NMR)‐compatible perfusion system. Rat brains were cut into 400‐μm thick slices and perfused with artificial cerebrospinal fluid (aCSF) in a 10‐mm NMR tube inside a 600‐MHz NMR spectrometer. Four experimental conditions were tested: (1) continuous perfusion with aCSF with glucose and normoxia, and (2) 30‐, (3) 60‐, or (4) 120‐min periods of OGD followed by reperfusion of aCSF containing glucose and normoxia. The energetic state of perfused brain slices was measured using phosphorus (31P) NMR and metabolite changes were measured using proton (1H) NMR. aCSF samples were collected every 30 min and analyzed using 1H NMR. The sample temperature was maintained at 36.7 ± 0.1°C and was checked periodically throughout the experiments. Brain slice histology was compared before and after OGD in the perfusion system using hematoxylin–eosin–saffron staining. NMR data clearly distinguished three severity groups (mild, moderate, and severe) after 30, 60, and 120 min of OGD, respectively, compared with the control group. 31P NMR spectra obtained from controls showed that phosphocreatine levels were stable for 5 h inside the perfusion system. Control 1H NMR spectra showed that lactate, N‐acetylaspartic acid, glutamate, γ‐aminobutyric acid, and creatine metabolite levels were stable over time, with lactate levels having a tendency to gradually increase due to the recirculation of the aCSF in the perfusion system. A controlled and reproducible perfusion system was established to study the energetic and metabolic changes in rat brain slices during and after OGD of varying severity.
A controlled and reproducible model to study metabolic changes during oxygen–glucose deprivation (OGD) was established in rat brain using an NMR‐compatible perfusion system. The viability of brain slices was maintained for more than 5 h under controlled conditions designed to ensure adequate oxygen and nutrient supply, as well as a physiological temperature of 37°C. NMR data clearly distinguished three severity groups (mild, moderate, and severe) after 30, 60, and 120 min of OGD, respectively, compared with the control group.
Type C hepatic encephalopathy (HE) is a complex neuropsychiatric disorder occurring as a consequence of chronic liver disease. Alterations in energy metabolism have been suggested in type C HE, but ...in vivo studies on this matter remain sparse and have reported conflicting results. Here, we propose a novel preclinical 18F-FDG PET methodology to compute quantitative 3D maps of the regional cerebral metabolic rate of glucose (CMRglc) from a labelling steady-state PET image of the brain and an image-derived input function. This quantitative approach shows its strength when comparing groups of animals with divergent physiology, such as HE animals. PET CMRglc maps were registered to an atlas and the mean CMRglc from the hippocampus and the cerebellum were associated to the corresponding localized 1H MR spectroscopy acquisitions. This study provides for the first time local and quantitative information on both brain glucose uptake and neurometabolic profile alterations in a rat model of type C HE. A 2-fold lower brain glucose uptake, concomitant with an increase in brain glutamine and a decrease in the main osmolytes, was observed in the hippocampus and in the cerebellum. These novel findings are an important step towards new insights into energy metabolism in the pathophysiology of HE.
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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.
•Neurotransmitter changes found in rat maternal depression long time after paradigma.•Neurotransmitters modulated by mirtazapine.
Three-dimensional digital brain atlases represent an important new generation of neuroinformatics tools for understanding complex brain anatomy, assigning location to experimental data, and planning ...of experiments. We have acquired a microscopic resolution isotropic MRI and DTI atlasing template for the Sprague Dawley rat brain with 39μm isotropic voxels for the MRI volume and 78μm isotropic voxels for the DTI. Building on this template, we have delineated 76 major anatomical structures in the brain. Delineation criteria are provided for each structure. We have applied a spatial reference system based on internal brain landmarks according to the Waxholm Space standard, previously developed for the mouse brain, and furthermore connected this spatial reference system to the widely used stereotaxic coordinate system by identifying cranial sutures and related stereotaxic landmarks in the template using contrast given by the active staining technique applied to the tissue. With the release of the present atlasing template and anatomical delineations, we provide a new tool for spatial orientationanalysis of neuroanatomical location, and planning and guidance of experimental procedures in the rat brain. The use of Waxholm Space and related infrastructures will connect the atlas to interoperable resources and services for multi-level data integration and analysis across reference spaces.
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•High-resolution MRI and DTI template for the Sprague Dawley rat brain•Atlas of major anatomical structures with detailed delineation criteria•Internal landmarks for implementing ‘Waxholm Space’ spatial reference system•Cranial landmarks for translation to stereotaxic coordinate system•The template and atlas form a new tool for spatial orientation in the rat brain.
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