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Acute doi: 10.3791/55940 Published: June 22, 2017


In this study, the methodology is presented on how to get multiple in vivo Carries out electrophysiological recordings from the hyperdirect route under urethane anesthesia.


Convergent evidence shows that many neuropsychiatric disorders should be understood as disorders of large-scale neural networks. In order to better understand the pathophysiological basis of these diseases, it is necessary to precisely characterize the way in which the processing of information between the various neuronal parts of the circuit is disturbed. Using extracellular in vivo Electrophysiological recordings make it possible to precisely delimit the neural activity within a neural network. The use of this procedure has compared to alternative techniques, e.g. functional magnetic resonance imaging and calcium imaging, several advantages as it allows unique temporal and spatial resolution and does not rely on genetically modified organisms. However, the use of extracellular In vivo Recordings are limited as it is an invasive technique that cannot be universally applied. This article presents a simple and easy-to-use method with which it is possible to simultaneously record extracellular potentials such as local field potentials and multifunctional activities at multiple locations in a network. It details how precise alignment of subcortical nuclei can be achieved through a combination of stereotactic surgery and online analysis of multi-unit images. It shows how a complete network such as the hyperdirect cortical-basal ganglia loop in anesthetized animals can be examined in vivo .


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The recent cumulative evidence in various neuropsychiatric disorders such as Parkinson's disease (PD) and schizophrenia strongly suggests that their pathophysiology is due to critical dysfunction of enlarged neural circuits, often cortical and subcortical structures 1,2,3 include . According to this theory, the clinical manifestations of diseases arise as a result of impaired information processing capacity of a network of cells instead of individual cells or specific neuronal elements 1,2,3 . In order to improve the understanding of this complex group of neuropsychiatric diseases and to find new treatment options, it is necessary to characterize in detail the neuronal dynamics of these disordered networks in human patients and in animal models. An excellent method to study large networks in living subjects is multiple electrophysiological recordings of extracellular potentials 4 . With this method it is possible to assess local field potentials (LFPs) simultaneously, which primarily represent the temporal summation of excitatory and inhibitory postsynaptic currents and multi-unit activity (MUA) generated by presynaptic potentials. The recording of extracellular potentials has, compared to alternative methods to investigate networks, e.g. functional magnetic resonance imaging and calcium imaging, because it offers a higher temporal and spatial resolution and because it does not depend on genetically modified organisms. However, the use of extracellular In vivo Recordings are limited as it is an invasive technique that cannot be universally applied.

In vivo Electrophysiological recordings can be carried out on both awake and anesthetized animals 6 . Both methods have specific advantages and disadvantages. Studies in conscious animals allow the recording of brain signals while performing defined behavioral tasks, but are prone to movement-related and other artifacts 7,8 . Recordings in anesthetized animals, on the other hand, provide an opportunity to assess LFPs and MUA with a minimum of artifacts in highly defined cortical synchronization states, but the results also differ to some extent from what is seen in the awake compartments 9,10,11 can be found .

In recent years, it has been shown that sampling of LFPs is particularly useful for delineating pathological changes in network activity. A prominent example of this is research into the pathophysiology of PD in human patients and animal models of the disease, where it has been shown that increased beta oscillations in the cortical-basal ganglia loop are associated with Parkinson's motor symptoms 12,13 are linked. As a consequence of this research direction, it is currently being investigated whether beta oscillations can act as online feedback biomarkers for closed deep brain stimulation 14,15 could be used.

The present study provides a detailed description of the acute multi-stage in vivo electrophysiological recordings of LFPs and MUA in rats anesthetized with urethane are provided. It is shown how a complete network, such as the hyperdirect cortical-basal ganglia, can be characterized electrophysiologically with standard and customer-specific electrodes and how these electrodes can be constructed. Special emphasis is placed on how precise alignment of basal ganglia nuclei can be achieved by co-mining stereotactic surgery along with the online registration of MUAs.

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The experimental procedures were carried out in accordance with the German Animal Welfare Act (last revised in 2014) and the European regulations (2010/63 / EU). Experiments have been approved by the local animal welfare authority (LaGeSo, Berlin) and comply with the local department and international guidelines.

NOTE: In the method presented, two models of electrodes are used to record from the hyperdirect cortico-basal ganglia pathway that connects the primary motor cortex (M1) to the subthalamic nucleus (STN) and reticulate substantia nigra pars (SNr). For epidural electrocorticograms (ECoG) recordings from the M1 tailor-made low-resistance Ag / AgCl electrodes are used. The recordings of STN and SNr are carried out with commercially available high-resistance tungsten electrodes.

1. Construction of epidural Ag / AgCl epidural electrodes

  1. Take an approx. 5 cm long strip of 99.99% pure silver wire with a diameter of 200 μm and remove any coatings.
  2. Hold the tip of the wire, tip down, in a flame of a lighter or candle until the tip begins to melt. Wait until the tip is spherical and about 1 mm in diameter. Cut the preformed electrode to a total length of 15 mm from the beginning of the spherical tip to the end of the wire.
  3. Loosen a precision plug to the end of the wire that fits the electrophysiological recording system used. Cover the soldering point from the end of the wire to the connector with conductive silver paint. This helps conductivity and leads to better signal quality.
  4. After the conductive lacquer has dried, cover the soldering point with a 3 mm to 1 mm heat shrink tubing. Carefully use a watchmaker's hammer to smooth the spherical tip down to half the thickness.
  5. Put on examination gloves and take a lint-free cleaning cloth with 100% ethanol to remove dirt and grease.
  6. Place the electrodes in a 15 ml centrifuge tube or cell culture tube and fill it with household chlorine bleach (CAUTION, with 2.8 g sodium hypochlorite per 100 g solvent) until the spherical tip is completely covered.
    CAUTION: Chlorine bleach is corrosive; Always follow the manufacturer's safety instructions.
  7. After 23 min, remove the electrodes and rinse generously with distilled water. The successful application of a silver chloride layer appears as a homogeneous purple color change.
  8. Dry in the air After they are completely dry, take the electrodes with fine tweezers. With a fine brush, apply liquid electrical insulation. Start the wire right behind the electrode tip and cover everything up to the heat shrink tubing. Let the insulation dry for at least 2 hours.
  9. For quality control, check the electrical conductivity with a multimeter. If available, perform impedance tests at 1 kHz with a suitable impedance meter while the electrode and test probe are in an H containing 0.9% NaCl 2 O solution composed without touching each other. Impedance values ​​at 1 kHz should be approx. 8 kΩ.

2. Attach the electrodes to a stereotactic holder

NOTE: To record MUA and LFPs simultaneously, use tungsten microwire electrodes with an impedance of 1.5 MΩ. If the focus of the recordings is on high-quality recordings of individual units, choose microwire electrodes with a higher impedance (> 5 MΩ). If the goal of the study is solely on LFPs, electrodes with lower impedances may be acceptable. For small structures for which dorsoventral stereotaxic adjustments are often necessary, use electrode pairs with a suitable dorsoventral tip deposition (in this case 250 μm). In addition, this has the advantage of having a more local reference electrode if required. The stereotaxic coordinates are always measured from the lowest electrode and aRe calculated in terms of the Bregma.

  1. Take a standard stereotaxic electrode holder with acrylic block and clamp and place it on a flat surface in the field of view of a surgical microscope.
  2. Loosely fix the first pair of electrodes to the acrylic block of the holder with adhesive strips (3 mm x 8 mm) using fine tweezers. The electrodes should cover the acrylic block about 12 mm
  3. Carefully fix the second bipolar electrode next to the first electrode. To align the structures of the Hyperdirect path, the distance should be 2 mm ( illustration 1 ). For most standard Stereotax electrode holders, this is the adjacent recess. Use a caliper gauge to check. Different networks can be approached in the same way. To do this, the acrylic block can be rotated to a certain extent.
  4. Adjust the second pair of electrodes by carefully sliding them into a position where the most ventral tip is about 200, opposite the first electrode ( illustration 1 ). Do this under microscopic vision. Use a 30 G cannula (outer diameter 300 μm) to better estimate the distance.
  5. Press down on the tape and secure it with the holder's metal clamp.

3. Surgery

  1. For electrophysiological recordings, use urethane (CAUTION) for anesthesia.
    Caution: Urethane is toxic and carcinogenic, therefore always follow the safety regulations and the data sheet of the substance manufacturer.
  2. Prepare a solution of 200 mg / ml urethane in 0.9% NaCl saline solution.
  3. Administer a total of 1.3 g / kg body weight urethane intraperitoneally (IP). Depending on the rat exposure, it might make sense to split the dose into two doses with a 15-minute interval between injections to increase the safety of the anesthesia.
  4. Check the depth of anesthesia using pEdal withdrawal reflex and other appropriate reflexes. If the anesthesia is not deep enough to perform surgery, inject 0.15 g / kg body weight of Urethane-IP and wait another 15 min.
  5. Apply an eye ointment to prevent corneal drainage.
  6. Constantly monitor breathing rate and pedal withdrawal reflex during anesthesia. Use a small animal temperature controlled heating pad to ensure a physiological body temperature is maintained during surgery. Before starting the electrophysiological recordings, switch to a non-electrical alternative ( e.g. Sodium acetate head cushion).
  7. Shave the fur next to the dorsal side of the head for a clean surgical field. Disinfect the incision site with an appropriate surgical disinfectant. Fix the animal in the stereotactic frame.
  8. Make a 2 cm incision of the scalp in the sagittal direction with a scalpel. Use a scalpel to gently scrape off the skull aponeurosis and disinfect the skull. Use coTton buds that are in 3% H 2 O 2 have been soaked to remove the remaining tissue.
  9. Use an electrocautery or thermal cooker to control bleeding, if necessary. Stop bleeding from the skull bone and hypoderm if the bleeding does not stop spontaneously after 1-2 min and obstruct the view of the skull.
  10. Adjust the incisor rod until the head is positioned in the flat skull position, which means that the bregma and lambda are in the same plane as stereotaxic reference points. This is most important to achieve high surgical precision. Using a standard Stereotax rat alignment tool, calibrate the indicated tip to the bregma under microscopic vision, and adjust the cutting pliers until the designated points for the bregma and lambda on the tool touch the skull at the same time.
    NOTE: A view from one side with focused light from the other can help determine this condition. Alternatively, take a stereotaxic holder with a fine cannula and measure the dorsoventral coordinates of Bregma and lambda under microscopic vision. Adjust the cutting cell until the dorsoventral coordinates of bregma and lambda are the same.
  11. Using a stereotaxic holder with cannula, calibrate the bregma, and then calculate the position of all drill holes on the skull. With the stereotaxic holder, mark the positions of the holes to be drilled either by carefully scraping the skull or by using a surgical paint marker. The coordinates for this depend on the destinations, coordinates with reference to the bregma are for the Hyperdirect path in Table 1 given , including the suggested coordinates for cerebellar reference electrodes.
  12. Carefully drill all the holes with a micro-drill. Drill a common hole (approx. 2 mm x 3 mm in size) for the STN and SNr. All other drill holes should have a diameter of approx. 1 mm.
  13. Take two fine cannulas (at least 27G) and bend their tips to form a hooked shape, using a hard surface or forceps. Use this to remove any debris from the drill holes, and carefully cut and remove the dura mater in the common STN / SNr hole.
  14. Flush the drill holes with physiological saline solution. Apply a drop of physiological saline solution to the drill holes every 15 minutes to prevent the brain and dura from drying out.
  15. Take a micro drill and matching stainless steel micro screw ( z. B. an M 1.2mm x 2mm screw), drill a hole and screw a micro screw between the drill holes of the reference epidural electrodes above the cerebellum, do the same for the M1 epidural electrodes.
  16. Slide the self-made Ag / AgCl epidural electrodes into the drill holes for the reference electrodes and M1 electrodes. Guide the electrode tip with fine forceps and push it into the drill hole directly under the skull bone.
  17. Fix all epidural electrodes with two-component dental acrylic. Be careful not to cover the Bregma point and not interfere with the common STN / SNr hole.
  18. Insert the prepared holder with the tungsten microwire electrode into the stereotaxic frame.
  19. Calibrate the ventral electrode facing the STN to the bregma. Adjust to the calculated position over the common STN / SNr hole and lower the electrodes onto the brain under a microscopic view. Make sure the tungsten microwave electrodes go into the brain smoothly.

4. Electrophysiological mapping and recordings

NOTE: This step requires a Faraday cage and a multi-channel electrophysiological recording system with recording software that allows online filtering and online spike sorting. Preferably use a system that uses a preamplifier positioned near the animals head to keep electrical noise and artifacts to an absolute minimum.In addition to the tungsten microwire electrodes, at least one epidural and one reference electrode are required to record the hyperdirect path. It is recommended to insert epidural and referencE electrodes in pairs without touching each other, this helps with interference and enables different types of referencing in data analysis.

  1. Place a mobile Faraday cage over the stereotaxic frame. If there is only one stationary Faraday cage, gently move the stereotaxic frame into the Faraday cage while making sure that deep brain electrodes are not lowered into the brain until the stereotaxic frame is in its final position.
  2. Connect the electrodes to the head step of the electrophysiological setup. Make sure that the reference electrodes are connected to suitable reference channels.
  3. Set up the recording software: band pass filter (0.05-8.000 Hz) and amplify (gain 1,500-2,000x) the raw data signal. Use an online LFP and spike filter with appropriate settings (band pass filter 0.05-250 Hz for LFPs, band pass filter 300-8,000 Hz for MUA). Use a Butterworth filter for all filters.
  4. Set up a spike threshold, if applicable, for online spike sorting Most recording software allows you to set up a spike threshold, which is an amplitude value above which a signal will be marked as a spike by the software. This threshold can either be determined mathematically as a factor or standard deviation of the mean amplitude of the filtered spike signal or can preferably be determined by visual inspection of data segments <500 ms and graphically structured as a line above the signal noise.
    NOTE: The intent of establishing a spike threshold is to count spikes and sorting units to inform how many neurons are currently recorded and how their spikes are shaped.
  5. Slowly lower the tungsten microwire electrodes to 1 mm dorsal to the target, which is STN for hyperdirect way. Wait for the signal to stabilize if necessary.
  6. For electrophysiological mapping, advance the electrodes ventrally in steps of 100 μm. Evaluate the moistening pattern at every step the exterior and shape of spikes Compare these with the typical examples in Figure 2 . Often, dense nuclei show rapidly and continuously over several dorsoventral steps, while fibrous structures in subsequent ventral steps show low burning rates and less homogeneous spike activities.
  7. For the hyperdirect path, make sure that the ventral electrode is inside the STN.
    NOTE: The STN is achieved when there is a significant increase in MUA anterior to the zona incerta. Ventral to the STN, the spiking stops almost completely because the electrode has reached the internal capsule. If the most ventral electrode is in STN, the configuration of the tungsten microelectrodes takes care of the rear, second electrode in SNr. Small incremental dorsoventral fine-tuning may be necessary to record typical MUA in STN and SNr at the same time. Note that the frequency of MUA depends on the number of neurons actually picked up and on the level of activation.
  8. As soon as the electrodes are in the desired structures, set up online filtering and spike sorting (see Figure 4 ) and then start recording the data. Typical examples of the various cortical synchronization states that can be identified in the LFP records are shown in FIG Figure 3 shown .

5. End of the experiment

  1. When exposures are taken, slowly lift the electrodes out of the brain and immediately flush them with normal saline. The electrodes can be reused after thorough rinsing and visual inspection. Bending discharge electrodes
  2. Euthanize the animals by IP injection of an overdose of urethane (2.5 g / kg body weight).
    NOTE: Urethane should only be used for final procedures.
  3. If histological verification of electrode position or other histological staining procedure is required, remove the brain from the skull and process the tissue appropriately.
    NOTE: Depending on the intended staining method, transcardiac perfusion may be necessary. For the follow-up examination of the electrode position, a standard Nissl stain is sufficient in most cases to show the electrode trajectory in e.g. visualize coronal brain segments. Other approaches to facilitate histological target verification include the use of electrically induced lesions on the brain tissue by applying an electric current across the recording electrodes or the application of biocompatible dyes prior to electrode insertion 16,17 .

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Representative Results

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With the recording electrodes used herein, it is possible to sample LFPs from the primary motor cortex, the subthalamic nucleus and the substantia nigra pars reticulata and MUA from the STN and SNr. Initially, LFPs and multi-unit activities are recorded together in one broadband signal. Then LFPs and MUAs are separated by band pass filters (0.05-250 Hz for LFPs and 300-4000 Hz for MUA).

For the correct alignment of subcortical nuclei, especially small structures such as the STN, it is advantageous to align the planned stereotactic coordinates with the MUA signal recorded online. The MUA pattern can be recorded for the electrode track that is aligned with the STN characteristic curve ( Figure 2 ) 9,20 .

For later steps of the analysis it is often mandatory to define individual units from the multi-unit activity according to the principle component analysis ( Figure 4 ).

In the LFP recordings from the M1, two spontaneously alternating cortical synchronization states can be identified: the activated state (AS) and the state of slow wave activity (SWA) ( Figure 3 ) 18,19 . While the SWA state is dominated by slow oscillations with a high amplitude of around 1 Hz, the AS is characterized by faster oscillations with a lower amplitude ( Figure 3 ).

Figure 1: Structure of the Deep Brain Microwire electrodes in a standard stereotaxic holder. Note the tip separation between A, the pair of electrodes for the STN and B, the pair of electrodes for the SNr in the dorsoventral direction of approx. 200 μm and anteroposterior direction of approx. 2 mm.Please click here to see a larger version of this figure.

Figure 2: Characteristic multi-unit activity from a dorsoventral electrode trajectory targeting the STN. ( A. ) Multi-unit images of the ventral posteromedial thalamic nucleus (VPM), the zona incerta (ZI), the subthalamic nucleus (STN) and the substantia nigra pars reticularis (SNr). The VPM shows sparse and irregularly spaced high amplitude peaks. This pattern of spikes stops as one approaches the ZI. When the electrode enters the STN, a typical high frequency ignition pattern with short bursts of medium amplitude can be observed. The SNr can be identified by its high amplitude and regular firing pattern. ( B) STN trajectories based on images from a rat stereotactic atlas 21 are superimposed. Upper part: coronal plane. Lower part: sagittal plane. Note the transfer of the electrode tip by the VPM and ZI. Please click here to see a larger version of this figure.

Figure 3. Cortical synchronization states in LFP recordings from the primary motor cortex during urethane anesthesia. ( A. ) Representative 600 s LFP recording of the primary motor cortex. Periods of time with high frequency, low amplitude activity corresponding to the activated state (i) and periods of time with a slower rhythm and high Er amplitude, which corresponds to the slow wave activity state (ii), can be differentiated. ( B. ) Corresponding time-frequency curve over an interval of 600 s, which shows the 0-20 Hz relative power of the LFPs shown in (A). Warm colors indicate higher relative performance. Please click here to see a larger version of this figure.

Figure 4: Sorting of individual units from STN multi-unit activity. ( A. ) Three-dimensional view of device clusters in the feature space after the principal component analysis. Each cluster represents a putative unit. ( B. ) Spike waveforms and spike waveform mean values ​​corresponding to the clusters in (A ).0fig4large.jpg "target =" _ blank "> Please click here to see a larger version of this figure.

Coordinates of BregmaSTNSNrM1Reference 1Reference 2
Anterior-posterior -3.6 -4,8 +3.0 -10,0 -10,0
Medial-lateral +2,5 +2,5 +3.0 +3.0 -3,0
Dorsal-ventral -8.0 n / A n / A n / A n / A

Table 1: Stereotaxic coordinates for the recording of the Hyperdirect CoRtico-basal ganglia pathway. All points are measured in mm from the Bregma reference point on the skull; Na- not applicable

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The present study demonstrates the method of recording extracellular electrophysiological signals simultaneously from multiple locations on a given network using the example of the hyperdirect cortico-basal ganglia pathway connecting the M1 to the STN and SNr in rodents.

A critical step in the recording of small subcortical structures such as the STN is the precisely guided insertion of the recording electrodes into the target. In the method presented, the support of two decisive steps ensures a high level of targeting accuracy. In preparing the animal for the stereotactic apparatus before the electrodes are inserted into the brain, it is imperative that the skull is in the "flat skull" position 22 is brought . To achieve the flat skull position, the position of the incisor rod of the stereotactic frame is changed up to the heights of the Bregma and Lambda reference points oN the skull is on the same dorsoventral plane 21 . Only by securing this position can coordinates found in stereotactic atlases be applied with high precision to the respective laboratory animal, since the atlases are in the flat skull position 21 based. The experimental evidence also proves that the aiming accuracy that an individualized flat skull position uses, a fixed adjustment of the cutting pliers 23 is superior. The position of the recording electrodes in the dorsoventral plane should be fine-tuned by continuously registering the multiple activity. The different cores and white fabric structures along the electrode track show characteristic fire patterns ( Figure 2 ) with which the position of the electrode 9,20 can be readjusted.

Another important step in the presented method is the placement of the eternity electrode.In the protocol presented, a position above the cerebellar cortex was chosen, since at this point the reference electrode does not recognize the cortical-basal ganglia activity, which was the focus of the study. In studies with an interest in analytical methods that are prone to volume conduction, a local reference should be preferred 5 .

Urethane is a widely used anesthetic for the uptake of neural extracellular potentials in animal research 11,18,24,25,26 . The reason for this is that a single dose of urethane can produce a stable and long lasting anesthetic for 8-12 hours with only limited depression of central nervous system activity compared to other anesthetics 27 . However, urethane anesthesia also activates the sympathetic nervous system, leading to undesirable side effects such as e.g. Hyperglycemia can result. Because of its long-lasting effects and the lack of a potent drug to combat its anesthetic effects, urethane should not be used for repeated experiments separated by hours or days. If multiple admission sessions are planned on the same animal, or if there is a technical reason not to use urethane, gas anesthesia with isoflurane and injections of drugs such as ketamine and xylazine can be viable electrophysiological alternatives In vivo Be experiments 28,29 The disadvantage of these anesthetic regimens is that they require more monitoring and adjustments than urethane use because of its short half-life and the accumulation of medication over time. There is also evidence that urethane may interfere less with physiological B. Rain activity than other anesthetics 30 .

All recording conditions detailed herein determine how the received data can be further processed and analyzed offline. It is therefore imperative to adapt all settings to the requirements of the planned analysis steps. Since there are many options for analyzing multichannel extracellular recordings, the use of available open source toolboxes can be beneficial 31 .

The recording of extracellular potentials in vivo is a method that offers a unique temporal and spatial resolution of brain signals that is superior to alternative methods such as functional magnetic resonance imaging and calcium imaging. The presented method can not only be applied to the recording of the hyperdirect path, but can easily be adapted to a variety of other experimental models and research questionsF "> 24 ,32,33. Since it is a stereotactic surgery, there are many levels of research where it cannot be used and where a non-invasive method should be chosen.

In the future, a combination of the presented multi-site extracellular recording method with optogenetic tools should be realized in order to further improve our understanding of the network dysfunction underlying various neuropsychiatric diseases in order to find new treatments.

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The authors have nothing to reveal.


We thank the Deutsche Forschungsgemeinschaft (DFG), KFO 247, for funding our study.


SurnameCompanyCatalog NumberComments
Ag / AgCl custom epidural electrodesGoodfellow GmbH
D-61213 Bad Nauheim, Germany
[email protected]
Product-ID AG005127 for 99.99% silver wireAg / AgCl electrodes will allow for better signal quality, but may only be used in acute experiments. Possible replacement: Stainless steel electrodes
Stereotaxic holder with acrylic blockDavid Kopf Instruments,
7324 Elmo Street, Tujunga, CA 91042, USA
Product ID Model 1770 Standard Electrode HolderMake sure the acrylic block has recesses which suit the electrode setup for the desired target. Acrylic blocks can easily be modified with a file to obtain the desired configuration. Possible replacement: Self-constructed electrode holders
Tungsten microwire electrodes 1.5 MΩ
18247-D Flower Hill Way Gaithersburg, Maryland, 20879 USA
Product ID WE3ST31.5A5-250umThe 1.5 MΩ is necessary to record MUA and LFP at the same time. Possible replacement: Microelectrodes of different materials can be used. The electrodes have to be straight, robust and as thin as possible.
Council alignment toolDavid Kopf Instruments,
7324 Elmo Street, Tujunga, CA 91042, USA
Product ID Model 944 Rat Alignment ToolAllows the exact orientation of the brain to match stereotaxic atlases. Possible replacement: Stereotaxic holder with a cannula
Two-component dental acrylicAssociated Dental Products Ltd.
Kemdent Works, Purton, Swindon
Wiltshire, SN5 4HT, United Kingdom
Simplex Rapid Powder Clear 225g, Product code: ACR803; Simplex Rapid Liquid 150ml, Product code: ACR920Depending in the electrodes used, superglue might be an easy alternative, if the electrodes are small and lightweight. Possible replacement: Superglue (cyanoacrylate-based)
Faraday cageSelf-constructionA proper Faraday cage will be the best protection from electromagnetic artifacts, but everything which can be formed into a box shape or applied to a frame and is made of conductive material may help. Possible replacement: Aluminum foil or copper mesh
Electrophysiological setup with recording software and online spike-sorting capabilitiesOmniPlex® Neural Data Acquisition System
Plexon Inc
6500 Greenville Avenue, Suite 700
Dallas, Texas 75206
United States
Offline sorting software is a potential alternative, multiple scripts and software can be found for free in the open source community.



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