Journal of neuroscience methods
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J. Neurosci. Methods · Mar 2007
Monitoring synaptic transmission in primary neuronal cultures using local extracellular stimulation.
Various techniques have been applied for the functional analysis of synaptic transmission in cultured neurons. Here, we describe a method of studying synaptic transmission in neurons cultured at high-density from different brain regions such as the cortex, striatum and spinal cord. We use postsynaptic whole-cell recordings to monitor synaptic currents triggered by presynaptic action potentials that are induced by brief stimulations with a nearby extracellular bipolar electrode. ⋯ We show that the size and kinetics of pharmacologically isolated inhibitory postsynaptic currents triggered by single action potentials or stimulus trains depend on the Ca2+ concentration, temperature and stimulation frequency. This method can be applied to study synaptic transmission in wildtype neurons infected with lentiviruses encoding various components of presynaptic release machinery, or in neurons from genetically modified mice, for example neurons carrying floxed genes in which gene expression can be acutely ablated by expression of Cre recombinase. The preparation described in this paper should be useful for analysis of synaptic transmission in inter-neuronal synapses formed by different types of neurons.
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J. Neurosci. Methods · Mar 2007
High-field diffusion tensor imaging of mouse brain in vivo using single-shot STEAM MRI.
Information about the microstructural organization of cerebral white matter that is accessible by magnetic resonance diffusion tensor imaging (DTI) gains increasing importance for studies of animal brain. Particular challenges occur for in vivo conditions as well as at high magnetic fields. ⋯ When compared to studies at 2.35 T, half Fourier DW STEAM MRI at 7 T yielded a substantial gain in signal-to-noise ratio (SNR) that could be invested either in a reduction of the measurement time or an increase of the spatial resolution. Thus, for a measurement time of 3h, DTI with a voxel size of 117 microm x 117 microm x 720 microm not only resulted in high-quality maps of the fractional anisotropy and main diffusion direction (MDD), but also allowed for fiber tracking of major mouse brain structures in vivo.
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J. Neurosci. Methods · Mar 2007
Low-density neuronal networks cultured using patterned poly-l-lysine on microelectrode arrays.
Synaptic activity recorded from low-density networks of cultured rat hippocampal neurons was monitored using microelectrode arrays (MEAs). Neuronal networks were patterned with poly-l-lysine (PLL) using microcontact printing (microCP). Polydimethysiloxane (PDMS) stamps were fabricated with relief structures resulting in patterns of 2 microm-wide lines for directing process growth and 20 microm-diameter circles for cell soma attachment. ⋯ Evoked responses of selected portions of the networks were produced by stimulation of specific electrode sites. In addition, the neuronal excitability of the network was increased by the bath application of high K(+) (10-12 mM). Application of DNQX, an AMPA antagonist, blocked all spontaneous activity, suggesting that the activity is excitatory and mediated through glutamate receptors.
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J. Neurosci. Methods · Mar 2007
Estimation of average muscle fiber conduction velocity from simulated surface EMG in pinnate muscles.
The aim of this simulation study was to assess the bias in estimating muscle fiber conduction velocity (CV) from surface electromyographic (EMG) signals in muscles with one and two pinnation angles. The volume conductor was a layered medium simulating anisotropic muscle tissue and isotropic homogeneous subcutaneous tissue. The muscle tissue was homogeneous for one pinnation angle and inhomogeneous for bipinnate muscles (two fiber directions). ⋯ The main factor biasing CV estimates was the propagation of action potentials in the two directions which influenced the recording due to the scatter of the projection of end-plate and tendon locations along the fiber direction, as a consequence of pinnation. The same problem arises in muscles with the line of innervation zone locations not perpendicular to fiber direction. These results indicate an important limitation in reliability of CV estimates from the interference EMG when the innervation zone and tendon locations are not distributed perpendicular to fiber direction.