Name: real-time dynamic collection of hippocampal extracellular fluid from conscious rats using a microdialysis system
Uploaded: 2022-10-21T14:00:00.000+00:00
Duration: 5 min 43 s
Description: Watch this Scientific Journal Video about Real-Time Dynamic Collection of Hippocampal Extracellular Fluid from Conscious Rats Using a Microdialysis System at JoVE.com

This work was supported by the National Natural Science Foundation of China (82104533), the Science &#38; Technology Department of Sichuan Province (2021YJ0175), and the China Postdoctoral Science Foundation (2020M683273). The authors would like to thank Mr. Yuncheng Hong, a senior equipment engineer at Tri-Angels D&#38;H Trading Pte. Ltd. (Singapore) for providing technical services for the microdialysis technique.

The experimental protocol was conducted in accordance with the requirements of the Use of Laboratory Animals and Institutional Animal Care and Use Committee at Chengdu University of Traditional Chinese Medicine (Record number: 2021-11). Male Sprague Dawley (SD) rats (280 &#177; 20 g, 6-8 weeks old) were used for the present study.
1. Brain microdialysis probe implantation surgery
<ol>
	<li>Use 3% and 1.5% isoflurane for the induction and maintenance of rat anesthesia, respectively, using an animal anesthesia system in an air-oxygen mixture at 0.6 L/min. Make sure that the rats are deeply anesthetized without both a pain reflex and a corneal reflex. Use veterinary ointment on the eyes to prevent dryness while under anesthesia.</li>
	<li>Remove the fur on the anesthetized rat&#39;s skull with an electric shaver in the preparation area. Then, fix the anesthetized rat on a stereotaxic brain locator. Disinfect the surgical site before the operation by applying povidone-iodine and ethanol 3x to the region of surgery with a sterile cotton ball. Apply&#160;bupivacaine topically for local analgesia. NOTE: The entire process of microdialysis-based HECF sample acquisition is illustrated in Figure 1.</li>
	<li>Make a 1.5 cm craniofacial incision down the middle with surgical scissors and remove the periosteum using surgical scissors and ophthalmic forceps.</li>
	<li>Consider the bregma as the basal position and pierce the endocranium to drill a 2 mm aperture at the anteroposterior (AP) position (-2 mm), the mediolateral (ML) position (-3.5 mm), and the dorsoventral (DV) position (-3.5 mm) (the hippocampal CA1 region) using a cranial drill.</li>
	<li>Fix the catheter stylet on the gripper of a stereotaxic brain locator and adjust the position of the microdialysis casing at the AP (-2 mm), ML (-3.5 mm), and DV (0 mm) positions. Adjust the DV value of the brain stereo locator, and implant the microdialysis casing into the CA1 region at a depth of 3.5 mm. 
	NOTE: Maintain the temperature of the animal at 37 &#176;C during the operation using an animal temperature maintainer.</li>
	<li>Drill three more apertures with a 2 mm diameter such that the three apertures form a triangle in which the probe aperture is centrally located. Implant screws into the apertures at a depth of 1 mm.</li>
	<li>Fix the probe catheter with dental cement and use a 4-0 surgical suture to close the skin. See Figure 2 for the placement of the probe.</li>
	<li>Place the rat in cages for 7 days to recover. Locally infiltrate bupivacaine (1.5 mg/kg) once daily post-surgery.&#160;Provide food and water ad libitum. Use sodium hyaluronate eye drops 3x a day to prevent dryness after the operation. 
	&#8203;NOTE: Perform all the procedures in a sterile surgical room. Do not leave the animal unattended until it has regained sufficient consciousness to maintain sternal recumbency under a 37 &#176;C condition. Do not return the animal that has undergone surgery to the company of other animals until fully recovered.</li>
</ol>
2. Microdialysis system connection and probe check
<ol>
	<li>Connect the microdialysis pump, microsyringe, awake activity device, and cryogenic sample collector according to the manufacturer&#39;s instructions. Install the microsyringe with ACSF on the microdialysis pump and set the microdialysis pump to a rate of 1 &#181;L/min to discharge the air in the pipeline.</li>
	<li>Connect the pipeline and brain microdialysis probe (membrane: PAES; membrane length: 4 mm; membrane OD: 0.5 mm; cut-off: 20 kDa; shaft length: 14 mm). Operate the microdialysis pump at a rate of 1 &#181;L/min to inject ACSF into the probe until the surface of the probe is slightly moist. Immerse the probe in heparin sodium injection solution for subsequent use. 
	&#8203;NOTE: If a big stream of the ACSF falls from the semipermeable membrane of the probe, as seen with the naked eye under gravity, replace the probe with a new one.</li>
</ol>
3. Collection of HECF from the awake rat
<ol>
	<li>Insert the brain microdialysis probe into the probe catheter and place the rat in a chamber (height: 360 mm; diameter: 400 mm) with padding to make sure the rats are free to move around.</li>
	<li>Connect the pipeline, microsyringe pump, and brain microdialysis probe. Harness the rat via the hole at the top of the rat restraint device and the stainless-steel swivels.</li>
	<li>Turn on the multi-channel swivel controller to avoid intertwining the microdialysis pipelines during the free movement of the rat. Turn on the microsyringe pump and pump the ACSF at a rate of 1 &#181;L/min. Collect HECF periodically after a 60 min equilibration of the microdialysis HECF collection system.</li>
	<li>Ensure that the flow rate of the HECF samples in the refrigerated fraction collector is consistent with ACSF infusion. Collect 20 &#181;L of HECF and automatically change to the next sampling tube. Take care to check whether the probe membrane is damaged when inserting the probe.</li>
</ol>
4. Measurement of the osmotic pressure for the HECF
<ol>
	<li>Turn on the osmometer and log in to the detection system. Click on the Cal button on the touch screen and click on the Res button on the page to clear the previous calibration memory.</li>
	<li>Install a 1.5 mL tube containing 100 &#181;L of pure water without bubbles on the measuring head. Pull the measuring head to the bottom of the cold hydrazine container.</li>
	<li>Enter the sample number 0 on the touch screen and confirm to test. Quickly dip the diode needle into the sample tube, and then quickly pull it out to induce crystallization of the sample at a temperature of -6.2 &#176;C.</li>
	<li>Wait for the screen to display: Push measure head up and click on Cal and Cal 0 in turn to calibrate. Perform measurements with a 300 mOsm calibration solution and measure the osmotic pressure of the HECF samples as described above. 
	&#8203;NOTE: Wipe the measuring head with a soft paper towel after calibration or measurement. The HECF samples with no bubbles should be mixed well.</li>
</ol>
5. Maintenance of the microdialysis system and devices after sampling
<ol>
	<li>Take out the brain microdialysis probe from the probe catheter after sampling termination. Immerse the probe in deionized water and lavage with deionized water for 12 h to remove stranded salt depositions from the pipeline and the probe.</li>
	<li>Remove the probe to place into a 0.05% trypsin solution at 4 &#176;C. Dry the pipelines in an air-dry oven at 25 &#176;C and store them at room temperature. 
	&#8203;NOTE: The microdialysis probes are expensive and this step can increase the reusability of the probes. Proteins that adhere to the probe surface can be digested by trypsin solution to prevent the probe membrane from being blocked by proteins, and trypsin had no effect on the probe material.</li>
</ol>
6. Animal treatment after sampling
<ol>
	<li>After sampling, painlessly euthanize the rats by making them inhale 1.5% isoflurane, followed by an overdose of 5% isoflurane in accordance with animal ethics.</li>
</ol>

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The authors have nothing to disclose.

The pathogenesis of CNS diseases is still not fully understood, which hinders the development of new therapies and drugs. Studies have shown that most CNS diseases are closely related to hippocampal lesions20,21,22. The proposed brain microdialysis technique can target specific regions of the brain, especially the hippocampus, which makes it stand out from the traditional approach of collecting HECF. Probes are placed in the CA1...

Central nervous system (CNS) diseases with high morbidities, such as neurodegenerative disease, traumatic brain injury, high-altitude hypoxia-induced brain injury, and ischemic stroke, are crucial causes of the growing mortality worldwide1,2,3. Real-time monitoring of cytokines and protein changes in specific brain regions contributes to the diagnostic accuracy of CNS diseases and brain pharmacokinetic studies after medication. Traditional scientific research uses brain tissue homogenate or a manual collection of animal interstitial brain fluid for the detection of specific substances and for pharmacokinetic studies. However, this has some shortcomings, such as a limited sample size, the inability to dynamically observe the changes of indicators, and uneven sampling quality4,5,6. Cerebrospinal fluid, an interstitial fluid, protects the brain and spinal cord from mechanical damage. Its composition is different from that of the serum due to the existence of the blood-brain barrier (BBB)7. Direct analysis of cerebrospinal fluid samples is more conducive to disclosing the mechanism of CNS lesions and drug discovery. Inevitably, the cerebrospinal fluid samples, manually obtained directly from the cisterna magna and cerebral ventricles through a syringe, have disadvantages of blood contamination, a random chance of sample collection, uncertainty of quantity, and almost no multiple retrieval possibility8,9. More notably, conventional interstitial brain fluid sampling methods cannot obtain samples from damaged brain regions, which hinders the exploration of the pathogenesis of CNS diseases in specific brain regions and the efficacy evaluation of targeted ethnomedicine therapies9,10.
Brain microdialysis is a technique for sampling interstitial brain fluid in awake animals11. The microdialysis system imitates vascular permeability with the help of a probe implanted in the brain. The microdialysis probe is armed with a semi-permeable membrane and is implanted in specific brain regions. After perfusion with isotonic artificial cerebrospinal fluid (ACSF), the dialyzed interstitial brain fluid can be favorably collected with the benefits of small sample sizes, continuous sampling, and dynamic observation12,13. In terms of location, brain microdialysis probes can be selectively implanted into brain structures or cranial cisterns of interest14. An observation of abnormal levels of an endogenous substance in the hippocampal extracellular fluid (HECF) suggests the occurrences of CNS diseases or the pathogenesis of disease. Several studies have shown that the biomarkers for CNS diseases, such as D-amino acids in schizophrenia, &#946;-amyloid and tau proteins in Alzheimer&#39;s disease, neurofilament light chains in traumatic brain injury, and ubiquitin carboxy-terminal hydrolase L1s in hypoxic ischemia encephalopathy, can be analyzed in cerebrospinal fluid15,16,17. A chemical analysis method based on the brain microdialysis sampling technique can be used to monitor dynamic changes of exogenous compounds such as active ingredients of ethnomedicine, which diffuse and distribute in specific brain regions14.
This article presents the specific process of dynamic HECF acquisition in awake rats and measures its osmotic pressure to ensure sample quality.

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real-time dynamic collection of hippocampal extracellular fluid from conscious rats using a microdialysis system

A variety of central nervous system (CNS) diseases are associated with changes in the composition of hippocampal extracellular fluid (HECF). However, difficulty in obtaining HECF in real time from conscious rats has long restricted the evaluation of CNS disease progression and the effectiveness of ethnomedicine therapy. Encouragingly, a brain microdialysis technique can be used for continuous sampling with the advantages of dynamic observation, quantitative analysis, and a small sampling size. This allows the monitoring of changes in the extracellular fluid content for compounds from traditional herbs and their metabolites in the brain of living animals. The aim of this study was thus to accurately implant a cerebrospinal fluid microdialysis probe into the hippocampal region of Sprague Dawley (SD) rats with a three-dimensional brain stereotaxic apparatus, cutting off molecular weights greater than 20 kDa. The high-quality HECF was then obtained from conscious rats using a microdialysis sampling control system with an adjustable sampling rate from 2.87 nL/min - 2.98 mL/min. In conclusion, our protocol provides an efficient, rapid, and dynamic method to obtain HECF in awake rats with the help of microdialysis technology, which provides us with unlimited possibilities to further explore the pathogenesis of CNS-related diseases and evaluate drug efficacy.

Following the above experimental protocol and the sampling parameters set in Table 1, water-like, colorless, and transparent rat HECF was obtained at the set sampling rate (Figure 1K). The osmotic pressure of the obtained rat HECF was 290-310 mOsm/L, which can indirectly ensure the quality of samples18,19.
<img alt="Figure 1" class="xfigimg" src="...

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Real-Time Dynamic Collection of Hippocampal Extracellular Fluid from Conscious Rats Using a Microdialysis System

The protocol here provides a detailed real-time dynamic sampling of extracellular fluid from the hippocampus of awake rats using a microdialysis system.

A variety of central nervous system (CNS) diseases are associated with changes in the composition of hippocampal extracellular fluid (HECF). However, ...

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Research

JoVE Journal

Neuroscience

2.3K Views.  Chengdu University of Traditional Chinese Medicine. Hippocampale extracellulaire vloeistof en crowd by brain microdialyse techniek draagt bij aan het monitoren van de ziekte specifieke micro van centrale zenuwstelsel ziekten. Hersenmicrodialyse technisch bereikt dynamische en de continue inquisitie van interstitiële hersenvloeistof in specifieke hersengebieden van niet-verdoofde ratten. Begin met het fixeren van de verdoofde rat op een stereotaxische hersenzoeker en veeg het geschoren chirurgische gebied drie keer voor de operatie af met een ...

Video: Real-Time Dynamic Collection of Hippocampal Extracellular Fluid from Conscious Rats Using a Microdialysis System

Survivable Stereotaxic Surgery in Rodents 

The ability to measure extracellular basal levels of neurotransmitters in the brain of awake animals allows for the determination of effects of different systemic challenges (pharmacological or physiological) to the CNS. For example, one can directly measure how the animal's midbrain dopamine projections respond to dopamine-releasing drugs like d-amphetamine or natural stimuli like food. In this video, we show you how to implant guide cannulas targeting specific sites in the rat brain, how to insert and implant a microdialysis probe and how to use high performance liquid chromatography coupled with electrochemical detection (HPLC-EC) to measure extracellular levels of oxidizable neurotransmitters and metabolites. Local precise introduction of drugs through the microdialysis probe allows for refined work on site specificity in a compound s mechanism of action. This technique has excellent anatomical and chemical resolution but only modest time resolution as microdialysis samples are usually processed every 20-30 minutes to ensure detectable neurotransmitter levels. Complementary ex vivo tools (i.e., slice and cell culture electrophysiology) can assist with monitoring real-time neurotransmission.

Survivable Stereotaxic Surgery in Rodents

The monitoring of extracellular neurotransmitter levels in distinct brain regions of freely moving animals offers insights on the link between neurotransmitter release and behavior. In vivo microdialysis coupled with electrochemical detection provides excellent anatomical and chemical resolution; and information on how basal neurotransmission is altered by pharmacological or physiological manipulations.

The ability to measure extracellular basal levels of neurotransmitters in the brain of awake animals allows for the determination of effects of different ...

Biology

Hippocampal Insulin Microinjection and In vivo Microdialysis During Spatial Memory Testing

Glucose metabolism is a useful marker for local neural activity, forming the basis of methods such as 2-deoxyglucose and functional magnetic resonance imaging. However, use of such methods in animal models requires anesthesia and hence both alters the brain state and prevents behavioral measures. An alternative method is the use of in vivo microdialysis to take continuous measurement of brain extracellular fluid concentrations of glucose, lactate, and related metabolites in awake, unrestrained animals. This technique is especially useful when combined with tasks designed to rely on specific brain regions and/or acute pharmacological manipulation; for example, hippocampal measurements during a spatial working memory task (spontaneous alternation) show a dip in extracellular glucose and rise in lactate that are suggestive of enhanced glycolysis1-3,4-5, and intrahippocampal insulin administration both improves memory and increases hippocampal glycolysis6. Substances such as insulin can be delivered to the hippocampus via the same microdialysis probe used to measure metabolites. The use of spontaneous alternation as a measure of hippocampal function is designed to avoid any confound from stressful motivators (e.g. footshock), restraint, or rewards (e.g. food), all of which can alter both task performance and metabolism; this task also provides a measure of motor activity that permits control for nonspecific effects of treatment. Combined, these methods permit direct measurement of the neurochemical and metabolic variables regulating behavior.

Hippocampal Insulin Microinjection and In vivo Microdialysis During Spatial Memory Testing

Modulation of hippocampally-dependent spatial working memory by direct intrahippocampal microinjection, accompanied and followed by in vivo microdialysis for metabolites in conscious, behaving animals.

Glucose metabolism is a useful marker for local neural activity, forming the basis of methods such as 2-deoxyglucose and functional magnetic resonance ...

Tuning in the Hippocampal Theta Band In Vitro: Methodologies for Recording from the Isolated Rodent Septohippocampal Circuit

This protocol outlines the procedures for preparing and recording from the isolated whole hippocampus, of WT and transgenic mice, along with recent improvements in methodologies and applications for the study of theta oscillations. A simple characterization of the isolated hippocampal preparation is presented whereby the relationship between internal hippocampal theta oscillators is examined together with the activity of pyramidal cells, and GABAergic interneurons, of the cornu ammonis-1 (CA1) and subiculum (SUB) areas. Overall, we show that the isolated hippocampus is capable of generating intrinsic theta oscillations in vitro and that rhythmicity generated within the hippocampus can be precisely manipulated by optogenetic stimulation of parvalbumin-positive (PV) interneurons. The in vitro isolated hippocampal preparation offers a unique opportunity to use simultaneous field and intracellular patch-clamp recordings from visually-identified neurons to better understand the mechanisms underlying theta rhythm generation.

Tuning in the Hippocampal Theta Band In Vitro: Methodologies for Recording from the Isolated Rodent Septohippocampal Circuit

Here, we present a protocol for recording rhythmic neuronal network theta and gamma oscillations from an isolated whole hippocampal preparation. We describe the experimental steps from extraction of the hippocampus to details of field, unitary and whole-cell patch clamp recordings as well as optogenetic pacing of the theta rhythm.

This protocol outlines the procedures for preparing and recording from the isolated whole hippocampus, of WT and transgenic mice, along with recent ...

Recording Spatially Restricted Oscillations in the Hippocampus of Behaving Mice

The local field potential (LFP) emerges from ion movements across neural membranes. Since the voltage recorded by LFP electrodes reflects the summed electrical field of a large volume of brain tissue, extracting information about local activity is challenging. Studying neuronal microcircuits, however, requires a reliable distinction between truly local events and volume-conducted signals originating in distant brain areas. Current source density (CSD) analysis offers a solution for this problem by providing information about current sinks and sources in the vicinity of the electrodes. In brain areas with laminar cytoarchitecture such as the hippocampus, one-dimensional CSD can be obtained by estimating the second spatial derivative of the LFP. Here, we describe a method to record multilaminar LFPs using linear silicon probes implanted into the dorsal hippocampus. CSD traces are computed along individual shanks of the probe. This protocol thus describes a procedure to resolve spatially restricted neuronal network oscillations in the hippocampus of freely moving mice.

This protocol describes the recording of local field potentials with multi-shank linear silicon probes. Conversion of the signals using current source density analysis allows the reconstruction of local electrical activity in the mouse hippocampus. With this technique, spatially restricted brain oscillations can be studied in freely moving mice.

The local field potential (LFP) emerges from ion movements across neural membranes. Since the voltage recorded by LFP electrodes reflects the summed ...

In Vivo Microdialysis Method to Collect Large Extracellular Proteins from Brain Interstitial Fluid with High-molecular Weight Cut-off Probes

In vivo microdialysis is a powerful technique to collect ISF from awake, freely-behaving animals based on a dialysis principle. While microdialysis is an established method that measures relatively small molecules including amino acids or neurotransmitters, it has been recently used to also assess dynamics of larger molecules in ISF using probes with high molecular weight cut off membranes. Upon using such probes, microdialysis has to be run in a push-pull mode to avoid pressure accumulated inside of the probes. This article provides step-by-step protocols including stereotaxic surgery and how to set up microdialysis lines to collect proteins from ISF. During microdialysis, drugs can be administered either systemically or by direct infusion into ISF. Reverse microdialysis is a technique to directly infuse compounds into ISF. Inclusion of drugs in the microdialysis perfusion buffer allows them to diffuse into ISF through the probes while simultaneously collecting ISF. By measuring tau protein as an example, the author shows how its levels are altered upon stimulating neuronal activity by reverse microdialysis of picrotoxin. Advantages and limitations of microdialysis are described along with the extended application by combining other in vivo methods.

In Vivo Microdialysis Method to Collect Large Extracellular Proteins from Brain Interstitial Fluid with High-molecular Weight Cut-off Probes

In vivo microdialysis has enabled collection of molecules present in brain interstitial fluid (ISF) from awake, freely-behaving animals. In order to analyze relatively large molecules in ISF, the current article specifically focuses on the microdialysis protocol using probes with high molecular weight cut off membranes.

In vivo microdialysis is a powerful technique to collect ISF from awake, freely-behaving animals based on a dialysis principle. While microdialysis is an ...

Microdialysis of Excitatory Amino Acids During EEG Recordings in Freely Moving Rats

Microdialysis is a well-established neuroscience technique that correlates the changes of neurologically active substances diffusing into the brain interstitial space with the behavior and/or with the specific outcome of a pathology (e.g., seizures for epilepsy). When studying epilepsy, the microdialysis technique is often combined with short-term or even long-term video-electroencephalography (EEG) monitoring to assess spontaneous seizure frequency, severity, progression and clustering. The combined microdialysis-EEG is based on the use of several methods and instruments. Here, we performed in vivo microdialysis and continuous video-EEG recording to monitor glutamate and aspartate outflow over time, in different phases of the natural history of epilepsy in a rat model. This combined approach allows the pairing of changes in the neurotransmitter release with specific stages of the disease development and progression. The amino acid concentration in the dialysate was determined by liquid chromatography. Here, we describe the methods and outline the principal precautionary measures one should take during in vivo microdialysis-EEG, with particular attention to the stereotaxic surgery, basal and high potassium stimulation during microdialysis, depth electrode EEG recording and high-performance liquid chromatography analysis of aspartate and glutamate in the dialysate. This approach may be adapted to test a variety of drug or disease induced changes of the physiological concentrations of aspartate and glutamate in the brain. Depending on the availability of an appropriate analytical assay, it may be further used to test different soluble molecules when employing EEG recording at the same time.

Here, we describe a method for in vivo microdialysis to analyze aspartate and glutamate release in the ventral hippocampus of epileptic and non-epileptic rats, in combination with EEG recordings. Extracellular concentrations of aspartate and glutamate may be correlated with the different phases of the disease.

Microdialysis is a well-established neuroscience technique that correlates the changes of neurologically active substances diffusing into the brain ...

A Novel and Translational Rat Model of Concussion Combining Force and Rotation with In Vivo Cerebral Microdialysis

Persistent cognitive and motor symptoms are known consequences of concussions/mild traumatic brain injury (mTBIs) that can be partly attributable to altered neurotransmission. Indeed, cerebral microdialysis studies in rodents have demonstrated an excessive extracellular glutamate release in the hippocampus within the first 10 min following trauma. Microdialysis offers the clear advantage of in vivo neurotransmitter continuous sampling while not having to sacrifice the animal. In addition to the aforementioned technique, a closed head injury model that exerts rapid acceleration and deceleration of the head and torso is needed, as such a factor is not available in many other animal models. The Wayne State weight-drop model mimics this essential component of human craniocerebral trauma, allowing the induction of an impact on the head of an unrestrained rodent with a falling weight. Our novel and translational rat model combines cerebral microdialysis with the Wayne State weight-drop model to study, in lightly anesthetized and unrestrained adult rats, the acute changes in extracellular neurotransmitter levels following concussion. In this protocol, the microdialysis probe was inserted inside the hippocampus as region of interest, and was left inserted in the brain at impact. There is a high density of terminals and receptors in the hippocampus, making it a relevant region to document altered neurotransmission following concussion. When applied to adult Sprague-Dawley rats, our combined model induced increases in hippocampal extracellular glutamate concentrations within the first 10 min, consistent with the previously reported post-concussion symptomology. This combined weight-drop model provides a reliable tool for researchers to study early therapeutic responses to concussions in addition to repetitive brain injury, since this protocol induces a closed-head mild trauma.

Neurotransmitter alteration is a mechanism of neural dysfunction that occurs after concussion and contributes to the sometimes-catastrophic long-term consequences. This rat model combines microdialysis, allowing in vivo neurotransmitter quantification, with a weight-drop technique exerting rapid acceleration and deceleration of the head and torso, an important factor of human craniocerebral trauma.

Persistent cognitive and motor symptoms are known consequences of concussions/mild traumatic brain injury (mTBIs) that can be partly attributable to ...

Acute Mouse Brain Slicing to Investigate Spontaneous Hippocampal Network Activity

Acute rodent brain slicing offers a tractable experimental approach to gain insight into the organization and function of neural circuits with single-cell resolution using electrophysiology, microscopy, and pharmacology. However, a major consideration in the design of in vitro experiments is the extent to which different slice preparations recapitulate naturalistic patterns of neural activity as observed in vivo. In the intact brain, the hippocampal network generates highly synchronized population activity reflective of the behavioral state of the animal, as exemplified by the sharp-wave ripple complexes (SWRs) that occur during waking consummatory states or non-REM sleep. SWRs and other forms of network activity can emerge spontaneously in isolated hippocampal slices under appropriate conditions. In order to apply the powerful brain slice toolkit to the investigation of hippocampal network activity, it is necessary to utilize an approach that optimizes tissue health and the preservation of functional connectivity within the hippocampal network. Mice are transcardially perfused with cold sucrose-based artificial cerebrospinal fluid. Horizontal slices containing the hippocampus are cut at a thickness of 450 &#956;m to preserve synaptic connectivity. Slices recover in an interface-style chamber and are transferred to a submerged chamber for recordings. The recording chamber is designed for dual surface superfusion of artificial cerebrospinal fluid at a high flow rate to improve oxygenation of the slice. This protocol yields healthy tissue suitable for the investigation of complex and spontaneous network activity in vitro.

This protocol describes the preparation of horizontal hippocampal-entorhinal cortex (HEC) slices from mice exhibiting spontaneous sharp-wave ripple activity. Slices are incubated in a simplified interface holding chamber and recordings are performed under submerged conditions with fast-flowing artificial cerebrospinal fluid to promote tissue oxygenation and the spontaneous emergence of network-level activity.

Acute rodent brain slicing offers a tractable experimental approach to gain insight into the organization and function of neural circuits with single-cell ...

Dynamic Continuous Blood Extraction from Rat Heart via Noninvasive Microdialysis Technique

Dynamic analysis of blood components is of great importance in understanding cardiovascular diseases and their related diseases, such as myocardial infarction, arrhythmia, atherosclerosis, cardiogenic pulmonary edema, pulmonary embolism, and cerebral embolism. At the same time, it is urgent to break through the continuous heart blood sampling technique in live rats to evaluate the effectiveness of distinctive ethnic medicine therapy. In this study, a blood microdialysis probe was implanted in the right jugular vein of rats in a precise and noninvasive surgical procedure. Cardiac blood samples were then collected at a rate of 2.87 nL/min to 2.98 mL/min by connecting to an online microdialysis sample collection system. Even more momentously, the acquired blood samples can temporarily be stored in microdialysis containers at 4 &#176;C. The microdialysis-based online continuous blood collection program from rat heart has greatly guaranteed the quality of blood samples, advancing and invigorating the scientific rationality of the research on systemic cardiovascular diseases and evaluating ethnomedicine therapy from the perspective of hematology.

Dynamic Continuous Blood Extraction from Rat Heart via Noninvasive Microdialysis Technique

The present protocol describes a simple and efficient method for the real-time and dynamic collection of rat heart blood using the microdialysis technique.

Dynamic analysis of blood components is of great importance in understanding cardiovascular diseases and their related diseases, such as myocardial ...

Medicine

LFP Recording in Mouse Brain for Cognitive Research and Drug Analysis

Dual Extracellular Recordings in the Mouse Hippocampus and Prefrontal Cortex

The technique of recording local field potentials (LFPs) is an electrophysiological method used to measure the electrical activity of localized neuronal populations. It serves as a crucial tool in cognitive research, particularly in brain regions like the hippocampus and prefrontal cortex. Dual LFP recordings between these areas are of particular interest as they allow the exploration of interregional signal communication. However, methods for performing these recordings are rarely described, and most commercial recording devices are either expensive or lack adaptability to accommodate specific experimental designs. This study presents a comprehensive protocol for performing dual-electrode LFP recordings in the mouse hippocampus and the prefrontal cortex to investigate the effects of antipsychotic drugs and potassium channel modulators on LFP properties in these areas. The technique enables the measurement of LFP properties, including power spectra within each brain region and coherence between the two. Additionally, a low-cost, custom-designed recording device has been developed for these experiments. In summary, this protocol provides a means to record signals with high signal-to-noise ratios in different brain regions, facilitating the investigation of interregional information communication within the brain.

Author Spotlight: Studying Drug Impacts on Brain Signals Using Dual LFP Recording Protocol in Mice

This protocol outlines the use of a custom-designed recording device and electrodes to record local field potentials and investigate information flow in the mouse hippocampus and prefrontal cortex.

The technique of recording local field potentials (LFPs) is an electrophysiological method used to measure the electrical activity of localized neuronal ...

Real-Time Dynamic Collection of Hippocampal Extracellular Fluid from Conscious Rats Using a Microdialysis System

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