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Neuronal Firing Patterns and Models
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Neuronal firing patterns are fundamental for information coding in the brain. Some distinctive neuronal firing patterns have been observed in the mammalian brain and classified into a small number of classes that are referred to in the literature by special designations. It must be kept in mind, however, that these classifications are largely based on responses of neurons in vitro, that is, in an artificial environment outside the living body. Slices of neural tissue, generally ranging in thickness between 100 and 500 µm, are bathed in artificial cerebrospinal fluid, and intracellular or extracellular recordings are obtained from the neurons under investigation in response to applied current pulses of long duration and of various magnitudes. Using slices of neural tissue is very convenient because: (i) the slices can be rapidly prepared and are mechanically stable, in the absence of heart beat and respiratory pulsations, (ii) the extracellular environment can be readily altered, as may be desired, without the impediment of a blood-brain barrier, and (iii) neurons can be directly observed under a microscope, allowing accurate placement of recording and stimulating electrodes in the desired locations. In some cases, either neuron cultures are used instead of neural slices, or isolated, dissociated neurons having a cell body, a stump of axon and some of the proximal dendrites.
Natural Biopolymeric Nanoformulations for Brain Drug Delivery
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Nanocarriers for Brain Targeting, 2019
Josef Jampílek, Katarina Král’ová
Biocompatible starch-coated superparamagnetic iron oxide NPs (SPION) in buffered artificial cerebrospinal fluid injected into the brain parenchyma of anaesthetized rats were found to form a concentration gradient from the center of the injection site toward the periphery suggesting that they might be transported in the extracellular space as well as being internalized in nerve cells (Kim et al., 2003). PEG-modified, cross-linked starch-coated Fe2O3 NPs suitable for magnetic targeting showed improved plasma stability and enhanced tumor exposure of NPs in 9L-glioma rat model (Cole et al., 2011). The aminated, starch-coated, magnetic Fe2O3 NPs conjugated by β-glucosidase showed ca. 85% relative activity of the free enzyme but much better temperature stability and the application of an additional field on the surface of a tumor led to effective delivery of NPs into a subcutaneous tumor of a glioma-bearing mouse and the β-glucosidase activity in tumor lesions was about one order higher, with 2.14 of tumor/non-tumor enzyme activity (Zhou et al., 2013). Cationic protein protamine-loaded crosslinked and aminated starch-coated magnetic iron oxide NPs that were simultaneously PEGylated and heparinized were reported to be promising for simultaneous tumor targeting and imaging (Zhang et al., 2014b). They displayed 37-fold longer half-life (9.37 h) than heparin (0.15 h) and enabled extended exposure to tumor lesions in a flank 9L-glioma mouse model and reached 7-fold improvement of the tumor targeting ability over that of heparin (Zhang et al., 2013b).
Transcranial Magnetic and Electric Stimulation
Published in Ben Greenebaum, Frank Barnes, Biological and Medical Aspects of Electromagnetic Fields, 2018
Shoogo Ueno, Masaki Sekino, Tsukasa Shigemitsu
A tDCS-induced LTP in mouse motor cortex and a polarity-specific modulation of LTP induction in the rat hippocampus has been demonstrated. A link between DCS and synaptic plasticity has been established by experimental studies using an animal model. Ranieri et al. (2012) evaluated the effects of anodal and cathodal DCS on rat brain slice on long-term potentiation (LTP). To do this, they investigated the effects of anodal and cathodal DCS on Male Wistar rat coronal hippocampal slices on LTP and evaluated the mechanism underlying the observed effects of DCS on synaptic plasticity. And then, they explored the effect of DCS on the expression of two immediate early genes, c-fos and zif268. DCS was applied to the brain slice through two Ag-AgCl electrodes with 9 mm diameter submerged in artificial cerebrospinal fluid (aCSF) and connected to two poles of the DC stimulator. From this stimulator, a current 200–250 µA was delivered for 20 min. The expression of zif268 protein in the cornus ammonis (CA) region was increased in a subregion-specific manner after the application of both anodal and cathodal DCS. And in the CA and in dentate gyrus regions of hippocampal, the increase of c-fos protein expression was less pronounced. Brain-derived neurotrophic factor (BDNF) expression was found to be reduced in cathodal DCS stimulated slices. In conclusion, DCS modulates LTP induction in a polarity-specific manner and affects gene expression.
Neurophysiological and molecular approaches to understanding the mechanisms of learning and memory
Published in Journal of the Royal Society of New Zealand, 2021
Shruthi Sateesh, Wickliffe C. Abraham
The in vitro approach has been an invaluable tool for virtually every field of neuroscience. This technique allows the experimenter to record the monosynaptic field potentials using extracellular electrodes, as described above, or else make single cell recordings using patch clamp or intracellular recording techniques. These methods allow for detailed pharmacological, molecular and electrophysiological studies under highly controlled conditions. For this purpose, the brain is rapidly removed from anaesthetised animals and the hippocampus is dissected out and cut into thick transverse slices (300–400 µm). These slices are placed in a recording chamber where they are kept viable by continuous perfusion with oxygenated media (95% O2 and 5% CO2) containing appropriate ions including Na+, K+, Mg2+, Cl– and Ca2+, as well as glucose for energy, mimicking the endogenous cerebrospinal fluid. This bathing medium is thus termed artificial cerebrospinal fluid (ASCF) (Skrede and Westgaard 1971).
High-sensitivity and spatial resolution transient magnetic and electric field probes for transcranial magnetic stimulator characterizations
Published in Instrumentation Science & Technology, 2018
Qinglei Meng, Michael Daugherty, Prashil Patel, Sudhir Trivedi, Xiaoming Du, Elliot Hong, Fow-Sen Choa
To demonstrate this, we compared both types of probes (including electric field probe and cylindrical inductor probe) to measure the field at one certain position in the air and artificial cerebrospinal fluid (ACSF-Ecocyte Bioscience, salinity ∼0.9%) using the animal TMS as shown in Figure 3. The voltage that charged the capacitor C1 was set to 500 V. As Figure 10 illustrates, by comparing signals detected in each case, no significant difference between the measurements in the air and cerebrospinal fluid (CSF) liquid was observed for neither type of probe. The electric field probe detected a peak of 1200 mV in the air and 1240 mV in CSF liquid, only a 3.3% increase; and for the cylindrical inductor probe, the reading is 10.2 V in the air and 11.1 V in CSF. The 8.8% increase of peak voltage reading is attributed from the induced current in CSF. Comparison of three types of probes for electric field measurement is listed in Table 1, and it may require more detailed dynamic analysis including the driving current source generated from the capacitor bank, through the TMS coil, CSF conductance, and probe inductance, which will be done in future research.
Mechanical behavior and constitutive equations of porcine brain tissue considering both solution environment effect and strain rate effect
Published in Mechanics of Advanced Materials and Structures, 2022
Jingyu Wang, Yongrou Zhang, Zhenyu Jiang, Licheng Zhou, Zejia Liu, Yiping Liu, Bao Yang, Liqun Tang
The brain tissue was tested in four environments: artificial cerebrospinal fluid (ACF), normal saline (NS), deionized water (DW) and air environment (Air). The ACF was bought from Xin Fan Bio-technology Co., Ltd (Shanghai, China). At least 5 specimens were tested in each environment. All experiments were carried out at room temperature (25 °C), and we strictly controlled the external temperature. This is because the external temperature will largely affect the swelling ratio of the hydrogel materials [34], thereby affecting the mechanical behavior. The height of the brain tissue specimens was approximately between 11 and 13 mm. To ensure the strain rate of each specimen was lower than 0.001/s, the loading rate was set as 0.01 mm/s.