This work was supported by CHDI (A-12467), the German Research Foundation (Exc 257/1 and DFG Project-ID 327654276 &#8211; SFB 1315) and intramural Research Funds of the Charit&#233;. We thank K. T&#246;r&#246;k, St. George&#39;s, University of London, and N. Helassa, University of Liverpool, for the iGluu plasmid and many helpful discussions. D. Betances and A. Sch&#246;nherr provided excellent technical assistance.

The authors have nothing to disclose.

The experiments concern a question of general interest &#8212; synapse independency and its possible loss in the course of neurodegeneration, and we describe a new approach to identify affected synapses in acute brain slices from aged (&#62;1 year) mice. Taking advantage of the improved kinetic characteristics of the recently introduced glutamate sensor iGluu the experiments illuminate the relationship between synaptic glutamate release and uptake in a way that has not been possible before.
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The relative impact of each synaptic terminal belonging to a &#34;unitary connection&#34; (i.e., the connection between 2 nerve cells) is typically assessed by its influence on the initial segment of the postsynaptic neuron1,2. Somatic and/or dendritic recordings from postsynaptic neurons represent the most common and, until now, also the most productive means to clarify information processing under a top-down or vertical perspective3,4,5. However, the presence of astrocytes with their discrete and (in rodents) non-overlapping territories may contribute a horizontal perspective that is based on local mechanisms of signal exchange, integration and synchronization at synaptic sites6,7,8,9,10.
Because it is known that astroglia play, in general, a major role in the pathogenesis of neurodegenerative disease11,12 and, in particular, a role in the maintenance and plasticity of glutamatergic synapses13,14,15,16, it is conceivable that alterations in synaptic performance evolve in accordance with the state of astrocytes in the shared target area of afferent fibers with diverse origin. To further explore the target-/astroglia-derived local regulatory mechanisms in health and disease, it is necessary to evaluate individual synapses. The present approach was worked out to estimate the range of functional glutamate release and clearance indicators and to define criteria that may be used to identify dysfunctional (or recovered) synapses in brain areas most closely related to movement initiation (i.e., first of all in the motor cortex and dorsal striatum).
The striatum lacks intrinsic glutamatergic neurons. Therefore, it is relatively easy to identify glutamatergic afferents of extrastriatal origin. The latter mostly originate in the medial thalamus and in the cerebral cortex (see17,18,19,20 for more). Corticostriatal synapses are formed by the axons of pyramidal neurons localized in cortical layers 2/3 and 5. The respective axons form bilateral intra-telencephalic (IT) connections or ipsilateral connections via a fiber system that more caudally constitutes the pyramidal tract (PT). It has further been suggested that IT- and PT-type terminals differ in their release characteristics and size21,22. In view of these data, one could also expect some differences in the handling of glutamate.
The striatum is the most affected brain area in Huntington&#39;s disease (HD)5. Human HD is a severe genetically inherited neurodegenerative disorder. The Q175 mouse model offers an opportunity to investigate the cellular basis of the hypokinetic-rigid form of HD, a state that has much in common with parkinsonism. Starting at an age of about 1 year, homozygote Q175 mice (HOM) exhibit signs of hypokinesia, as revealed by measuring the time spent without movement in an open field23. The present experiments with heterozygote Q175 mice (HET) confirmed the previous motor deficits observed in HOM and, in addition, showed that the observed motor deficits were accompanied by a reduced level of the astrocytic excitatory amino acid transporter 2 protein (EAAT2) in the immediate vicinity of corticostriatal synaptic terminals24. It has therefore been hypothesized that a deficit in astrocytic glutamate uptake could lead to dysfunction or even loss of respective synapses25,26.
Here, we describe a new approach that allows one to evaluate single synapse glutamate clearance relative to the amount of the released neurotransmitter. The new glutamate sensor iGluu was expressed in corticostriatal pyramidal neurons. It was developed by Katalin T&#246;r&#246;k27 and represents a modification of the previously introduced high-affinity but slow glutamate sensor iGluSnFR28. Both sensors are derivatives of the enhanced green fluorescent protein (EGFP). For spectral and kinetic characteristics, see Helassa et al.27. Briefly, iGluu is a low-affinity sensor with rapid de-activation kinetics and therefore particularly well suited to study glutamate clearance at glutamate-releasing synaptic terminals. The dissociation time constant of iGluu was determined in a stopped-flow device, which rendered a Tauoff value of 2.1 ms at 20 &#176;C, but 0.68 ms when extrapolated to a temperature of 34 &#176;C27. Single Schaffer collateral terminals probed at 34 &#176;C with spiral laser scanning in the CA1 region of organotypic hippocampal cultures under a 2-photon microscope exhibited a mean time constant of decay of 2.7 ms.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Stereo microsope</td>
			<td>WPI</td>
			<td>PZMIII</td>
			<td>Precision Stereo Zoom Binocular Microscope</td>
		</tr>
		<tr>
			<td>Stereotaxic frame</td>
			<td>Stoelting</td>
			<td>51500D</td>
			<td>Digital Lab New Standard stereotaxic frame</td>
		</tr>
		<tr>
			<td>High speed drill equipment</td>
			<td>Stoelting</td>
			<td>514439V</td>
			<td>Foredom K1070 cromoter Kit</td>
		</tr>
		<tr>
			<td>Injection system</td>
			<td>Stoelting</td>
			<td>53311</td>
			<td>Quintessential Stereotaxic Injector (QSI)</td>
		</tr>
		<tr>
			<td>Hamilton syringe 5 &#181;l</td>
			<td>Hamilton</td>
			<td>87930</td>
			<td>75RN Syr (26s/51/2)</td>
		</tr>
		<tr>
			<td>Laser positioning system</td>
			<td>Rapp OptoElectronic</td>
			<td>UGA-40</td>
			<td>UGA-40</td>
		</tr>
		<tr>
			<td>Blue laser for iGluu excitation</td>
			<td>Rapp OptoElectronic</td>
			<td>DL-473-020-S</td>
			<td>473 nm laser</td>
		</tr>
		<tr>
			<td>Dichroic mirror for 473 nm</td>
			<td>Rapp OptoElectronic</td>
			<td>ROE TB-355-405-473</td>
			<td>Dichroic</td>
		</tr>
		<tr>
			<td>1P upright microscope</td>
			<td>Carl Zeiss</td>
			<td>000000-1066-600</td>
			<td>Axioskop 2 FS Plus</td>
		</tr>
		<tr>
			<td>Objective 63x/1.0</td>
			<td>Carl Zeiss</td>
			<td>421480-9900</td>
			<td>W Plan-Apochromat</td>
		</tr>
		<tr>
			<td>4x objective</td>
			<td>Carl Zeiss</td>
			<td>44-00-20</td>
			<td>Achroplan 4x/0,10</td>
		</tr>
		<tr>
			<td>Dichroic mirror for iGluu</td>
			<td>Omega optical</td>
			<td>XF2030</td>
			<td></td>
		</tr>
		<tr>
			<td>Emission filter for iGluu</td>
			<td>Omega optical</td>
			<td>XF3086</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichroic mirror</td>
			<td>Omega optical</td>
			<td>QMAX_DI580LP</td>
			<td></td>
		</tr>
		<tr>
			<td>Emission filter for autofluorescence subtr.</td>
			<td>Omega optical</td>
			<td>QMAX EM600-650</td>
			<td></td>
		</tr>
		<tr>
			<td>sCMOS camera</td>
			<td>Andor</td>
			<td>ZYLA4.2PCL10</td>
			<td>ZYLA 4.2MP Plus</td>
		</tr>
		<tr>
			<td>Acqusition software</td>
			<td>Andor</td>
			<td>4.30.30034.0</td>
			<td>Solis</td>
		</tr>
		<tr>
			<td>AD/DA converter</td>
			<td>HEKA Elektronik</td>
			<td>895035</td>
			<td>InstruTECH LIH8+8</td>
		</tr>
		<tr>
			<td>Aquisition software</td>
			<td>HEKA Elektronik</td>
			<td>895153</td>
			<td>TIDA5.25</td>
		</tr>
		<tr>
			<td>Electrode positioning system</td>
			<td>Sutter Instrument</td>
			<td>MPC-200</td>
			<td>Micromanipulator</td>
		</tr>
		<tr>
			<td>Electrical stimulator</td>
			<td>Charite workshops</td>
			<td>STIM-26</td>
			<td></td>
		</tr>
		<tr>
			<td>Slicer</td>
			<td>Leica</td>
			<td>VT1200 S</td>
			<td>Vibrotome</td>
		</tr>
		<tr>
			<td>Brown/Flaming-type puller</td>
			<td>Sutter Instr</td>
			<td>SU-P1000</td>
			<td>P-1000</td>
		</tr>
		<tr>
			<td>Glass tubes for injection pipettes</td>
			<td>WPI</td>
			<td>1B100F3</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass tubes forstimulation pipettes</td>
			<td>WPI</td>
			<td>R100-F3</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrodotoxin</td>
			<td>Abcam</td>
			<td>ab120054</td>
			<td>TTX</td>
		</tr>
		<tr>
			<td>iGluu plasmid</td>
			<td>Addgene</td>
			<td>106122</td>
			<td>pCI-syn-iGluu</td>
		</tr>
		<tr>
			<td>Q175 mice</td>
			<td>Jackson Lab</td>
			<td>27410</td>
			<td>Z-Q175-KI</td>
		</tr>
	</tbody>
</table>

single synapse indicators of glutamate release and uptake in acute brain slices from normal and huntington mice

Synapses are highly compartmentalized functional units that operate independently on each other. In Huntington&#39;s disease (HD) and other neurodegenerative disorders, this independence might be compromised due to insufficient glutamate clearance and the resulting spill-in and spill-out effects. Altered astrocytic coverage of the presynaptic terminals and/or dendritic spines as well as a reduced size of glutamate transporter clusters at glutamate release sites have been implicated in the pathogenesis of diseases resulting in symptoms of dys-/hyperkinesia. However, the mechanisms leading to the dysfunction of glutamatergic synapses in HD are not well understood. Improving and applying synapse imaging we have obtained data shedding new light on the mechanisms impeding the initiation of movements. Here, we describe the principle elements of a relatively inexpensive approach to achieve single synapse resolution by using the new genetically encoded ultrafast glutamate sensor iGluu, wide-field optics, a scientific CMOS (sCMOS) camera, a 473 nm laser and a laser positioning system to evaluate the state of corticostriatal synapses in acute slices from age appropriate healthy or diseased mice. Glutamate transients were constructed from single or multiple pixels to obtain estimates of i) glutamate release based on the maximal elevation of the glutamate concentration [Glu] next to the active zone and ii) glutamate uptake as reflected in the time constant of decay (TauD) of the perisynaptic [Glu]. Differences in the resting bouton size and contrasting patterns of short-term plasticity served as criteria for the identification of corticostriatal terminals as belonging to the intratelencephalic (IT) or the pyramidal tract (PT) pathway. Using these methods, we discovered that in symptomatic HD mice ~40% of PT-type corticostriatal synapses exhibited insufficient glutamate clearance, suggesting that these synapses might be at risk to excitotoxic damage. The results underline the usefulness of TauD as a biomarker of dysfunctional synapses in Huntington mice with a hypokinetic phenotype.

Identification of two types of corticostriatal glutamatergic varicosities 
IT and PT afferents originate in layer 2/3 and 5, respectively, and exhibit differential ramification and termination patterns in the ipsilateral and contralateral (IT terminals only) striatum. Still little is known about the properties of glutamate release and clearance under repetitive activation conditions as observed during the initiation of movements, but it is well documented that the respective glutamate-releasing vari...

Watch this Scientific Journal Video about Single Synapse Indicators of Glutamate Release and Uptake in Acute Brain Slices from Normal and Huntington Mice at JoVE.com

Single Synapse Indicators of Glutamate Release and Uptake in Acute Brain Slices from Normal and Huntington Mice

We present a protocol to evaluate the balance between glutamate release and clearance at single corticostriatal glutamatergic synapses in acute slices from adult mice. This protocol uses the fluorescent sensor iGluu for glutamate detection, a sCMOS camera for signal acquisition and a device for focal laser illumination.

Synapses are highly compartmentalized functional units that operate independently on each other. In Huntington&#39;s disease (HD) and other ...

single-synapse-indicators-glutamate-release-uptake-acute-brain-slices

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Neuroscience

6.1K Views.  Charité - University Medicine. We present a protocol to evaluate the balance between glutamate release and clearance at single corticostriatal glutamatergic synapses in acute slices from adult mice. This protocol uses the fluorescent sensor iGluu for glutamate detection, a sCMOS camera for signal acquisition and a device for focal laser illumination.

Video: Single Synapse Indicators of Glutamate Release and Uptake in Acute Brain Slices from Normal and Huntington Mice

Preparation of Acute Hippocampal Slices from Rats and Transgenic Mice for the Study of Synaptic Alterations during Aging and Amyloid Pathology

The rodent hippocampal slice preparation is perhaps the most broadly used tool for investigating mammalian synaptic function and plasticity. The hippocampus can be extracted quickly and easily from rats and mice and slices remain viable for hours in oxygenated artificial cerebrospinal fluid. Moreover, basic electrophysisologic techniques are easily applied to the investigation of synaptic function in hippocampal slices and have provided some of the best biomarkers for cognitive impairments. The hippocampal slice is especially popular for the study of synaptic plasticity mechanisms involved in learning and memory. Changes in the induction of long-term potentiation and depression (LTP and LTD) of synaptic efficacy in hippocampal slices (or lack thereof) are frequently used to describe the neurologic phenotype of cognitively-impaired animals and/or to evaluate the mechanism of action of nootropic compounds. This article outlines the procedures we use for preparing hippocampal slices from rats and transgenic mice for the study of synaptic alterations associated with brain aging and Alzheimer's disease (AD)1-3. Use of aged rats and AD model mice can present a unique set of challenges to researchers accustomed to using younger rats and/or mice in their research. Aged rats have thicker skulls and tougher connective tissue than younger rats and mice, which can delay brain extraction and/or dissection and consequently negate or exaggerate real age-differences in synaptic function and plasticity. Aging and amyloid pathology may also exacerbate hippocampal damage sustained during the dissection procedure, again complicating any inferences drawn from physiologic assessment. Here, we discuss the steps taken during the dissection procedure to minimize these problems. Examples of synaptic responses acquired in "healthy" and "unhealthy" slices from rats and mice are provided, as well as representative synaptic plasticity experiments. The possible impact of other methodological factors on synaptic function in these animal models (e.g. recording solution components, stimulation parameters) are also discussed. While the focus of this article is on the use of aged rats and transgenic mice, novices to slice physiology should find enough detail here to get started on their own studies, using a variety of rodent models.

This article outlines procedures for preparing hippocampal slices from rats and transgenic mice for the study of synaptic alterations associated with brain aging and age-related neurodegenerative diseases, such as Alzheimer&#x2019;s disease.

The rodent hippocampal slice preparation is perhaps the most broadly used tool for investigating mammalian synaptic function and plasticity. The ...

GABA-activated Single-channel and Tonic Currents in Rat Brain Slices

The GABAA channels are present in all neurons and are located both at synapses and outside of synapses where they generate phasic and tonic currents, respectively 4,5,6,7 The GABAA channel is a pentameric GABA-gated chloride channel. The channel subunits are grouped into 8 families (&alpha;1-6, &beta;1-3, &gamma;1-3, &delta;, &#949;, &theta;, &pi; and &rho;). Two alphas, two betas and one 3rd subunit form the functional channel 8. By combining studies of sub-type specific GABA-activated single-channel molecules with studies including all populations of GABAA channels in the neuron it becomes possible to understand the basic mechanism of neuronal inhibition and how it is modulated by pharmacological agents.
We use the patch-clamp technique 9,10 to study the functional properties of the GABAA channels in alive neurons in hippocampal brain slices and record the single-channel and whole-cell currents. We further examine how the channels are affected by different GABA concentrations, other drugs and intra and extracellular factors. For detailed theoretical and practical description of the patch-clamp method please see The Single-Channel Recordings edited by B Sakman and E Neher 10.

We use the patch-clamp technique to measure GABA-activated single-channel currents (GABAA channels, GABAA receptors) and the synaptic and tonic currents they generate in neurons. Activation of the channels decreases neuronal excitability in health and disease 1,2,3,4.

The GABAA channels are present in all neurons and are located both at synapses and outside of synapses where they generate phasic and tonic currents, ...

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

In vivo Postnatal Electroporation and Time-lapse Imaging of Neuroblast Migration in Mouse Acute Brain Slices

The subventricular zone (SVZ) is one of the main neurogenic niches in the postnatal brain. Here, neural progenitors proliferate and give rise to neuroblasts able to move along the rostral migratory stream (RMS) towards the olfactory bulb (OB). This long-distance migration is required for the subsequent maturation of newborn neurons in the OB, but the molecular mechanisms regulating this process are still unclear. Investigating the signaling pathways controlling neuroblast motility may not only help understand a fundamental step in neurogenesis, but also have therapeutic regenerative potential, given the ability of these neuroblasts to target brain sites affected by injury, stroke, or degeneration.
In this manuscript we describe a detailed protocol for in vivo postnatal electroporation and subsequent time-lapse imaging of neuroblast migration in the mouse RMS. Postnatal electroporation can efficiently transfect SVZ progenitor cells, which in turn generate neuroblasts migrating along the RMS. Using confocal spinning disk time-lapse microscopy on acute brain slice cultures, neuroblast migration can be monitored in an environment closely resembling the in vivo condition. Moreover, neuroblast motility can be tracked and quantitatively analyzed. As an example, we describe how to use in vivo postnatal electroporation of a GFP-expressing plasmid to label and visualize neuroblasts migrating along the RMS. Electroporation of shRNA or CRE recombinase-expressing plasmids in conditional knockout mice employing the LoxP system can also be used to target genes of interest. Pharmacological manipulation of acute brain slice cultures can be performed to investigate the role of different signaling molecules in neuroblast migration. By coupling in vivo electroporation with time-lapse imaging, we hope to understand the molecular mechanisms controlling neuroblast motility and contribute to the development of novel approaches to promote brain repair.

In vivo Postnatal Electroporation and Time-lapse Imaging of Neuroblast Migration in Mouse Acute Brain Slices

Neuroblast migration is a fundamental event in postnatal neurogenesis. We describe a protocol for efficient labeling of neuroblasts by in vivo postnatal electroporation and subsequent visualization of their migration using time-lapse imaging of acute brain slices. We include a description for the quantitative analysis of neuroblast dynamics by video tracking.

The subventricular zone (SVZ) is one of the main neurogenic niches in the postnatal brain. Here, neural progenitors proliferate and give rise to ...

Electrophysiological and Morphological Characterization of Neuronal Microcircuits in Acute Brain Slices Using Paired Patch-Clamp Recordings

The combination of patch clamp recordings from two (or more) synaptically coupled neurons (paired recordings) in acute brain slice preparations with simultaneous intracellular biocytin filling allows a correlated analysis of their structural and functional properties. With this method it is possible to identify and characterize both pre- and postsynaptic neurons by their morphology and electrophysiological response pattern. Paired recordings allow studying the connectivity patterns between these neurons as well as the properties of both chemical and electrical synaptic transmission. Here, we give a step-by-step description of the procedures required to obtain reliable paired recordings together with an optimal recovery of the neuron morphology. We will describe how pairs of neurons connected via chemical synapses or gap junctions are identified in brain slice preparations. We will outline how neurons are reconstructed to obtain their 3D morphology of the dendritic and axonal domain and how synaptic contacts are identified and localized. We will also discuss the caveats and limitations of the paired recording technique, in particular those associated with dendritic and axonal truncations during the preparation of brain slices because these strongly affect connectivity estimates. However, because of the versatility of the paired recording approach it will remain a valuable tool in characterizing different aspects of synaptic transmission at identified neuronal microcircuits in the brain.

Patch-clamp recordings and simultaneous intracellular biocytin filling of synaptically coupled neurons in acute brain slices allow a correlated analysis of their structural and functional properties. The aim of this protocol is to describe the essential technical steps of electrophysiological recording from neuronal microcircuits and their subsequent morphological analysis.

The combination of patch clamp recordings from two (or more) synaptically coupled neurons (paired recordings) in acute brain slice preparations with ...

Preparation of Acute Brain Slices Using an Optimized N-Methyl-D-glucamine Protective Recovery Method

This protocol is a practical guide to the N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. Numerous recent studies have validated the utility of this method for enhancing neuronal preservation and overall brain slice viability. The implementation of this technique by early adopters has facilitated detailed investigations into brain function using diverse experimental applications and spanning a wide range of animal ages, brain regions, and cell types. Steps are outlined for carrying out the protective recovery brain slice technique using an optimized NMDG artificial cerebrospinal fluid (aCSF) media formulation and enhanced procedure to reliably obtain healthy brain slices for patch clamp electrophysiology. With this updated approach, a substantial improvement is observed in the speed and reliability of gigaohm seal formation during targeted patch clamp recording experiments while maintaining excellent neuronal preservation, thereby facilitating challenging experimental applications. Representative results are provided from multi-neuron patch clamp recording experiments to assay synaptic connectivity in neocortical brain slices prepared from young adult transgenic mice and mature adult human neurosurgical specimens. Furthermore, the optimized NMDG protective recovery method of brain slicing is compatible with both juvenile and adult animals, thus resolving a limitation of the original methodology. In summary, a single media formulation and brain slicing procedure can be implemented across various species and ages to achieve excellent viability and tissue preservation.

Preparation of Acute Brain Slices Using an Optimized N-Methyl-D-glucamine Protective Recovery Method

This protocol demonstrates the implementation of an optimized N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. A single media formulation is used to reliably obtain healthy brain slices from animals of any age and for diverse experimental applications.

This protocol is a practical guide to the N-methyl-D-glucamine (NMDG) protective recovery method of brain slice preparation. Numerous recent studies have ...

Recording Synaptic Plasticity in Acute Hippocampal Slices Maintained in a Small-volume Recycling-, Perfusion-, and Submersion-type Chamber System

Even though experiments on brain slices have been in use since 1951, problems remain that reduce the probability of achieving a stable and successful analysis of synaptic transmission modulation when performing field potential or intracellular recordings. This manuscript describes methodological aspects that might be helpful in improving experimental conditions for the maintenance of acute brain slices and for recording field excitatory postsynaptic potentials in a commercially available submersion chamber with an outflow-carbogenation unit. The outflow-carbogenation helps to stabilize the oxygen level in experiments that rely on the recycling of a small buffer reservoir to enhance the cost-efficiency of drug experiments. In addition, the manuscript presents representative experiments that examine the effects of different carbogenation modes and stimulation paradigms on the activity-dependent synaptic plasticity of synaptic transmission.

This protocol describes the stabilization of the oxygen level in a small volume of recycled buffer and methodological aspects of recording activity-dependent synaptic plasticity in submerged acute hippocampal slices.

Even though experiments on brain slices have been in use since 1951, problems remain that reduce the probability of achieving a stable and successful ...

Evaluation of Synapse Density in Hippocampal Rodent Brain Slices

In the brain, synapses are specialized junctions between neurons, determining the strength and spread of neuronal signaling. The number of synapses is tightly regulated during development and neuronal maturation. Importantly, deficits in synapse number can lead to cognitive dysfunction. Therefore, the evaluation of synapse number is an integral part of neurobiology. However, as synapses are small and highly compact in the intact brain, the assessment of absolute number is challenging. This protocol describes a method to easily identify and evaluate synapses in hippocampal rodent slices using immunofluorescence microscopy. It includes a three-step procedure to evaluate synapses in high-quality confocal microscopy images by analyzing the co-localization of pre- and postsynaptic proteins in hippocampal slices. It also explains how the analysis is performed and gives representative examples from both excitatory and inhibitory synapses. This protocol provides a solid foundation for the analysis of synapses and can be applied to any research investigating the structure and function of the brain.

A protocol for accurately identifying and analyzing synapses in hippocampal slices using immunofluorescence is outlined in this article.

In the brain, synapses are specialized junctions between neurons, determining the strength and spread of neuronal signaling. The number of synapses is ...

Whole-cell Currents Induced by Puff Application of GABA in Brain Slices

Pharmacological administration is commonly used when conducting whole-cell patch-clamp recording in brain slices. One of the best methods of drug application during electrophysiological recording is the puff technique, which can be used to study the effect of pharmacological reagents on neuronal activities in brain slices. The greatest advantage of puff application is that the drug concentration around the recording site increases rapidly, thus preventing desensitization of membrane receptors. Successful use of puff application involves careful attention to the following elements: the concentration of the drug, the parameters of the puff micropipette, the distance between the tip of a puff micropipette and the neuron recorded, and the duration and pressure driving the puff (pounds per square inch, psi). This article describes a step-by-step procedure for recording whole-cell currents induced by puffing gamma-aminobutyric acid (GABA) onto a neuron of a prefrontal cortical slice. Notably, the same procedure can be applied with minor modifications to other brain areas such as the hippocampus and the striatum, and to different preparations, such as cell cultures.

We describe the puff technique, by which pharmacological reagents can be administered during whole-cell patch-clamp recording, and highlight various aspects of the features that are crucial for its success.

Pharmacological administration is commonly used when conducting whole-cell patch-clamp recording in brain slices. One of the best methods of drug ...

Evaluation of Hemisphere Lateralization with Bilateral Local Field Potential Recording in Secondary Motor Cortex of Mice

This article demonstrates complete, detailed procedures for both in vivo bilateral recording and analysis of local field potential (LFP) in the cortical areas of mice, which are useful for evaluating possible laterality deficits, as well as for assessing brain connectivity and coupling of neural network activities in rodents. The pathological mechanisms underlying Alzheimer&#39;s disease (AD), a common neurodegenerative disease, remain largely unknown. Altered brain laterality has been demonstrated in aging people, but whether or not abnormal lateralization is one of the early signs of AD has not been determined. To investigate this, we recorded bilateral LFPs in 3-5-month-old AD model mice, APP/PS1, together with littermate wild type (WT) controls. The LFPs of the left and right secondary motor cortex (M2), specifically in the gamma band, were more synchronized in APP/PS1 mice than in WT controls, suggesting a declined hemispheric asymmetry of bilateral M2 in this AD mouse model. Notably, the recording and data analysis processes are flexible and easy to carry out, and can also be applied to other brain pathways when conducting experiments that focus on neuronal circuits.

We present in vivo electrophysiological recording of the local field potential (LFP) in bilateral secondary motor cortex (M2) of mice, which can be applied to evaluate hemisphere lateralization. The study revealed altered levels of synchronization between the left and right M2 in APP/PS1 mice compared to WT controls.

This article demonstrates complete, detailed procedures for both in vivo bilateral recording and analysis of local field potential (LFP) in the cortical ...