The authors would like to acknowledge the Bioimaging Unit of Instituto de Medicina Molecular Jo&#227;o Lobo Antunes, for all the suggestions concerning image acquisition.
This project has received funding from the European Union&#8217;s Horizon 2020 research and innovation programme under grant agreement N&#186; 952455, Funda&#231;&#227;o para a Ci&#234;nciae Tecnologia (FCT) through Project PTDC/MEDFAR/30933/2017, and Faculdade de Medicina da Universidade de Lisboa.

The Portuguese law and European Union guidelines (2010/63/EU) were respected in all procedures regarding the protection of animals for scientific purposes. All methods described here were approved by the iMM&#8217;s Institutional Animal Welfare Body (ORBEA-iMM) and the National competent authority (DGAV &#8211; Dire&#231;&#227;o Geral de Alimenta&#231;&#227;o e Veterin&#225;ria).
1. Preparation of rhinal cortex-hippocampus slices
NOTE: The preparation of rhinal cortex-hippocampus slices uses P6-7 Sprague-Dawley rats.
<ol>
	<li>Culture setup and medium preparation
	<ol>
		<li>On the day before the culture, prepare the required media and place them at 4 &#176;C.</li>
		<li>Prepare dissection medium: 25 mM glucose in Gey&#39;s Balanced Salt Solution (GBSS).</li>
		<li>Prepare culture medium: 50% Opti-MEM, 25% HBSS, 25% Horse Serum (HS), 25 mM glucose, 30 &#181;g/mL Gentamycin.</li>
		<li>Prepare maintenance medium: Neurobasal-A (NBA), 2% B27, 1 mM L-glutamine, 30 &#181;g/mL Gentamycin, HS (15%, 10%, 5% and 0%).</li>
	</ol>
	</li>
	<li>Brain harvesting
	<ol>
		<li>Just before starting the culture, add 1.1 mL of culture medium to each well of the 6-well plate with a P1000 pipette and place it at 37 &#176;C.</li>
		<li>Place all the equipment (dissection microscope, tissue chopper, dissecting lamp, dissecting tools, electrodes, plates, inserts and filter papers) inside the biological safety cabinet and sterilize under UV light for 15 minutes.</li>
		<li>Adjust slice thickness to 350 &#181;m.</li>
		<li>Withdraw the GBSS from the fridge. Add 5 mL of GBSS to six Petri dishes. Six Petri dishes will be required per animal.</li>
		<li>Euthanize the rat pup. Perform decapitation by using a sharp scissor at the base of the brain stem of the animal.</li>
		<li>Wash the animal head three times in cold GBSS and take it inside the safety cabinet.</li>
	</ol>
	</li>
	<li>Tissue isolation and preparation of slices
	<ol>
		<li>Firmly insert sharp forceps into the eye sockets to hold the head.</li>
		<li>Using a thin scissor cut the skin/scalp along the midline starting from the vertebral foramen towards the frontal lobes and put it aside.</li>
		<li>Cut in the same way the skull and along the cerebral transverse fissure (space between brain and cerebellum). With curved long forceps, move it apart.</li>
		<li>Discard the olfactory bulbs with a spatula. Remove the brain from the head and place it in ice-cold GBSS with the dorsal surface faced up (Figure 1A).</li>
		<li>Insert the fine forceps into the cerebellum and go along the midline with the spatula opening each hemisphere very carefully (Figure 1B).</li>
		<li>With short curve forceps, carefully remove the excess tissue that covers the hippocampi, without touching the hippocampal structure. Then with a spatula, cut below each hippocampus (Figure 1C).</li>
		<li>Pick up one hemisphere and place it, with hippocampus facing up, onto a filter paper. Repeat the procedure with the other hemisphere and place it parallel to the first one, in the filter paper. Put the filter paper on the tissue chopper, with the hemispheres perpendicular to the blade, and cut the hemispheres in 350 &#956;m slices (Figure 1D).</li>
		<li>Place the sliced tissue into a Petri dish with cold GBSS (Figure 1E).</li>
		<li>Carefully separate the slices using the round tip electrodes (Figure 1F). Keep only the slices with a structurally intact rhinal cortex and hippocampus. DG and CA areas should be perfectly defined, as well as the entorhinal and perirhinal cortex (Figure 1G).</li>
		<li>Place each slice onto the insert (Figure 1H-I), with a spatula and a round tip electrode. Remove excess dissection medium around each slice with a P20 pipette (Figure 1J). Four rhinal cortex-hippocampus slices can be cultured in a single insert (Figure 1K).</li>
	</ol>
	</li>
	<li>Culture maintenance
	<ol>
		<li>Change the medium every other day.</li>
		<li>Warm up the medium at 37 &#176;C.</li>
		<li>Take the plates from the incubator. Pick up each insert by holding the plastic edge with forceps (Figure 1L).</li>
		<li>Use a free hand to aspirate the medium from the well. Place the insert back into the well and add 1 mL, with a P1000 pipette, of fresh warmed medium (Figure 1M). Repeat for all the inserts. Make sure no air bubbles are trapped between the membrane and the medium.</li>
	</ol>
	</li>
</ol>
NOTE: Epileptic-like slices undergo a gradual and controlled deprivation of serum in the medium. From 9 Days In Vitro (DIV) on, slices are maintained in NBA without HS14.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61330/61330fig01.jpg" /> 
Figure 1: Detailed procedure for the preparation of rhinal cortex-hippocampus organotypic slices.&#160;(A) Remove the brain from the head and place it in ice-cold GBSS with the dorsal surface faced up. (B) Insert the forceps into the cerebellum. Open the brain through the midline and remove the excess tissue over the hippocampus. (C) With a spatula cut below the hippocampus, as indicated by the arrows. (D) Place both hippocampi facing up and parallel to each other onto the filter paper and cut 350 &#181;m slices on the tissue chopper. (E) Place the sliced hippocampus in ice-cold GBSS. (F) Separate the slices with the help of round tipped glass electrodes. (G) Choose only the slices that depict an intact rhinal cortex and hippocampus. (H, I) With the help of a round tipped glass electrode push each slice to the spatula and place it on the insert. (J) Remove the GBSS surrounding the slice. (K) Place four slices per insert. (L) To change the medium, lift the insert and aspirate the medium with a glass pipette. (M) Add fresh medium by placing the pipette between the insert and the walls of the 6-wells plate. Make sure there are no air bubbles beneath the slices. <a href="https://www.jove.com/files/ftp_upload/61330/61330fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Electrophysiological recordings
NOTE: Electrophysiological recordings were performed in rhinal cortex-hippocampus organotypic slices at 7, 14 and 21 DIV in an interface-type chamber. Recordings were obtained with an amplifier, digitized and analyzed with software. All recordings were band-pass filtered (eight-pole Bessel filter at 60 Hz and Gaussian filter at 600 Hz).
<ol>
	<li>Setup preparation
	<ol>
		<li>Prepare 50 mL of NBA medium with 1 mL of B27 and 250 &#956;L of L-Glutamine. Warm up at 37 &#176;C.</li>
		<li>Set the electrophysiology setup in close circuit. Verify if the flow rate is 2 mL/min.</li>
		<li>Open the carbox (5% CO2/95% O2) valve and check the water level in the system.</li>
		<li>Put the filter paper in the interface recording chamber to drain excess medium and the lens cleaning paper beneath the frame to supply medium to the slice.</li>
		<li>Turn on the temperature controller, the amplifiers, and the micromanipulator.</li>
		<li>Let the temperature in the interface chamber stabilize at 37 &#176;C before starting the recordings.</li>
		<li>Prepare artificial cerebrospinal fluid (aCSF: 124 mM NaCl, 3mM KCl, 1.2 mM NaH2PO4, 25 mM NaHCO3, 10 mM glucose, 2 mM CaCl2, 1 mM MgSO4 with pH 7.4) and use it to fill the glass electrode with a syringe. Place it in the receiving electrode.</li>
	</ol>
	</li>
	<li>Recordings of spontaneous activity
	<ol>
		<li>Once the temperature is stable, remove the plate from the incubator and cut one slice from the insert with a highly sharp blade. Place it in a 60 mm plate with a drop of medium. Take it to the interface recording chamber.</li>
		<li>Place the slice in the interface chamber with the hippocampus to the bottom right. Place&#160;the receiving electrode in the CA3 pyramidal cell layer.</li>
		<li>Proceed to the continuous acquisition protocol and record for 30 min.</li>
	</ol>
	</li>
</ol>
3. PI uptake assay
NOTE: Cell death was assessed by monitoring the cellular uptake of the fluorescent dye propidium iodide (PI). PI is a polar compound, which enters cells with damaged cell membranes and interacts with DNA emitting red fluorescence (absorbance 493 nm, emission 630 nm). Since PI is not permeant to live cells, it is used to detect dead cells in a population.
<ol>
	<li>PI incubation
	<ol>
		<li>Prepare, in culture medium, a fresh 1:10 dilution of PI stock.</li>
		<li>For PI uptake assay remove the plate from the incubator and carefully raise the insert. Add 13 &#181;L of PI to the medium, with a P20 pipette, obtaining a final concentration of 2 &#181;M.&#160; Agitate slowly the plate before putting the insert back in place. Make sure there are no bubbles beneath the slices.</li>
		<li>Put the slices back in the 37 &#176;C incubator for 2&#160;h.</li>
		<li>Proceed with the immunohistochemistry protocol, as described in the next section. Cover the plates with aluminium, since PI is light sensitive.</li>
	</ol>
	</li>
</ol>
4. Immunohistochemistry
NOTE: In immunohistochemistry a neuron specific antibody, as well as antibodies able to discriminate resting and reactive phenotypes of microglia and astrocytes, were used to evaluate the extend of neuronal death and gliosis in rhinal cortex-hippocampus epileptic-like organotypic slices.
<ol>
	<li>Tissue fixation
	<ol>
		<li>Remove the plate from the incubator and aspirate the medium. Fix the slices with 4% paraformaldehyde (PFA) for 1 h at RT, by adding 1 mL of PFA beneath and above the slices, with a P1000 pipette.</li>
		<li>Remove the PFA and add 1 mL of PBS. Also add PBS beneath and above the slices.</li>
		<li>Keep the slices at 4 &#176;C, in PBS, until further use. Always put parafilm around the plates to avoid drying.</li>
	</ol>
	</li>
	<li>Immunostaining steps
	<ol>
		<li>Wash twice, 10 min each time, with 1 mL of PBS.</li>
		<li>Prepare permeabilization/blocking solution containing 1% Triton-X100, 10% HS and 10% BSA in PBS. Prepare 5% BSA solution.</li>
		<li>Draw two rectangles with the hydrophobic pen (Figure 2A). Cut the slices from the insert (Figure 2B) with a highly sharp blade. Put two slices per slide (Figure 2C) and add 140 &#181;L of permeabilization/blocking solution on the top of each slice, using a P200 pipette. Incubate for 3 h at RT.</li>
		<li>Dilute the primary antibodies to the working dilution in 5% BSA in PBS. Incubate with the primary antibodies overnight at 4 &#176;C.</li>
		<li>Incubate with the secondary antibodies for 4 h at RT. From this step on, protect the plate from light since fluorophores are being worked with.</li>
		<li>Place a 50 &#956;L drop of Hoechst solution on the top of each slice and incubate for 20 min at RT.</li>
		<li>Wash between incubations. Always wash three times, for 10 min each time, with PBS-T.</li>
		<li>Remove Hoechst and wash as recommended.</li>
		<li>Add 50 &#956;L of mounting medium on the top of each slice. Cover with a glass coverslip and surround with nail polish (Figure 2D).</li>
		<li>Let it dry at RT for 24 h.</li>
		<li>Visualize the immunostaining under a confocal microscope. Keep the stained slices at -20 &#176;C.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61330/61330fig02.jpg" /> 
Figure 2: Specific procedure for the immunohistochemistry assay.&#160;(A) With the hydrophobic pen draw two squares in the slide. (B) Cut the piece of insert that contains the slice. (C) Place each slice in the squares drawn with the hydrophobic pen and start the permeabilization/blocking step. (D) After concluding the protocol, finish by mounting the slices in mounting medium, covering with a glass coverslip and surrounding it with nail polish. <a href="https://www.jove.com/files/ftp_upload/61330/61330fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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The authors have nothing to disclose.

Animal models of epilepsy have been crucial for the discovery of many AEDs, however they require many animals and most of them are time-consuming due to the latent period for seizure onset. The low-magnesium induction of epileptiform activity in hippocampal acute slices has also been thoroughly revised in the literature3, but acute slices have a 6-12 h viability making it impossible to assess long-term changes. Organotypic slices can be maintain in culture from days to weeks, allowing to overcome the short viability time of acute slices, and models of epileptogenesis in organotypic hippocampal slices have been proposed3,7,8.
Here we describe the preparation of organotypic slices, comprising the rhinal cortex and the hippocampus. These slices take 15-20 min to prepare per animal, starting from animal sacrifice until placement of slices onto the inserts, and 6-8 slices per hemisphere can be obtained. Extra care must be taken when opening the hemisphere to expose the hippocampus and when removing the tissue from the filter paper after slicing. Excess tissue above the hippocampus can also compromise the slice integrity during slicing.
Rhinal cortex-hippocampus organotypic slices depict an evolving epileptic-like activity resembling in vivo epilepsy. After one week in culture, most slices depict mixed interictal and ictal-like activity, which progresses to solely ictal-like events with time in culture. So far, we have recorded few interictal discharges in slices with 2-3 weeks. In this system, epileptic-like activity appears to develop faster than in organotypic hippocampal slices. This might be attributed to the presence of the rhinal cortex, which preserves most of the functional input to the hippocampus. To fully address this issue, a complete characterization of the epileptic signals displayed by these slices throughout time in culture, such as number and duration of ictal events, together with their amplitude and frequency, is currently being performed.
This system can be maintained in culture for more than three weeks, and mimics many molecular correlates of epilepsy, such as neuronal death, activation of microglia and astrocytes and increased production of pro-inflammatory cytokines14, allowing a long-term characterization of these aspects. It also represents an easy-to-use screening platform, where pharmacological interventions targeting specific cellular pathways can be implemented and potential therapeutic targets can be tested. Undoubtedly, the system herein presented can help to further enlighten the mechanisms of epileptogenesis.

Epilepsy, one of the most prevalent neurologic disorders worldwide, is characterized by the periodic and unpredictable occurrence of synchronized and excessive neuronal activity in the brain. Despite the various antiepileptic drugs (AEDs) available, one-third of patients with epilepsy are refractory to therapy1 and continue to experience seizures and cognitive decline. Furthermore, available AEDs hamper cognition due to their relatively generalized actions upon neuronal activity. Epileptogenesis is hard to study in humans, due to the multiple and heterogeneous epileptogenic injuries, long latent periods lasting months to decades, and the misleading effects of anticonvulsant treatment after the first spontaneous seizure.
The identification of potential therapeutic agents for the treatment of epilepsy has become possible due to animal models of epilepsy: 1) genetic models, which use genetically predisposed animals in which seizures occur spontaneously or in response to a sensory stimulus; 2) models of electrical stimulation-induced seizures; and 3) pharmacological models of seizure induction that use pilocarpine (a muscarinic receptor agonist), kainate (a kainate receptor agonist) or 4-aminopyridine (a potassium channel blocker), among others. These models were crucial in the understanding of the behavioral changes, as well as molecular and cellular mechanisms underlying epilepsy, and they have led to the discovery of many AEDs2.
Ex vivo preparations are also a powerful tool to explore the mechanisms underlying epileptogenesis and ictogenesis. Acute hippocampal slices, which enable electrophysiological studies of living cells over a 6-12 h period, and organotypic hippocampal slices that can be preserved in an incubator over a period of days or weeks have been extensively used in studies of epileptiform activity3.&#160;
Organotypic brain slices are prepared from explanted tissue and represent a physiological three-dimensional model of the brain. These slices preserve the cytoarchitecture of the region of interest and include all brain cells and their intercellular communication4.&#160;&#160;The most used region for long-term organotypic cultures is the hippocampus, as this region is affected by neuronal loss in multiple neurodegenerative conditions. They have been widely used to model brain disorders and are considered excellent tools for assessing a drug&#8217;s neuroprotective and therapeutic potential5,6. Models of epileptogenesis, stroke and A&#946;-induced toxicity were described in hippocampal organotypic slices7,8,9,10. Parkinson&#8217;s disease was explored in ventral mesencephalon and striatum, as well as cortex-corpus callosum-striatum-substantia nigra, organotypic slices11. Organotypic cerebellar slice cultures mimic many aspects of axon myelination and cerebellar functions and are a widespread model for investigating novel therapeutic strategies in multiple sclerosis12.
However, clinical research and animal models of epilepsy have suggested that the rhinal cortex, composed by perirhinal and entorhinal cortices, plays a role in seizure generation13. Thus, a model of epileptogenesis in rhinal cortex-hippocampus organotypic slices was established14. Under a gradual and controlled deprivation of serum, rhinal cortex-hippocampus organotypic slices depict evolving epileptic-like events, unlike analogous slices always kept in a serum-containing medium.
In epilepsy, as in many acute and chronic diseases of the central nervous system, the neurocentric vision fails to elucidate the mechanisms underlying disease onset and progression. Clinical and experimental evidence point to brain inflammation, in which microglia and astrocytes play a relevant role, as one of the key players contributing to the epileptic process. Pharmacological experiments in animal models of epilepsy suggest that antiepileptogenic effects can be achieved by targeting pro-inflammatory pathways, and nowadays neuroinflammation is regarded as a novel option for the development of therapeutic approaches for epilepsy15.
Here, we thoroughly describe the preparation of rhinal cortex-hippocampus organotypic slice cultures, as well as the details for recording spontaneous epileptiform activity from them. We highlight that this system mimics several neuroinflammatory aspects of epilepsy, being thus suitable to explore the role of glial cells and neuroinflammation in this pathology. Furthermore, it represents an easy-to-use platform for the screening of potential therapeutic approaches for epilepsy.

<table><tbody><tr><td>50 mL Centrifuge Tube, Conical Bottom</td><td>Corning</td><td>430829</td><td></td></tr><tr><td>70% Ethanol</td><td>Manuel Vieira, Lda</td><td>UN1170</td><td></td></tr><tr><td>Amplifier</td><td>Axon Instruments</td><td>Axoclamp 900A</td><td></td></tr><tr><td>Amplifier</td><td>Axon Instruments</td><td>Digidata 1440A</td><td></td></tr><tr><td>Anti-C3d (goat)</td><td>R&amp;amp;D Systems</td><td>AF2655</td><td>Dilute at a ratio 1:1000</td></tr><tr><td>Anti-CD68 (mouse)</td><td>Abcam</td><td>ab31630-125ug</td><td>Dilute at a ratio 1:250</td></tr><tr><td>Anti-GFAP (mouse)</td><td>Millipore SAS</td><td>MAB360</td><td>Dilute at a ratio 1:500</td></tr><tr><td>Anti-Iba1 (rabbit)</td><td>Abcam</td><td>ab108539</td><td>Dilute at a ratio 1:600</td></tr><tr><td>Anti-NeuN (rabbit)</td><td>Werfen</td><td>16712943S</td><td>Dilute at a ratio 1:500</td></tr><tr><td>Artificial cerebrospinal fluid (aCSF)</td><td></td><td></td><td>Homemade</td></tr><tr><td>B-27&amp;trade; Supplement (50X), serum free</td><td>Thermo Fisher Scientific</td><td>17504-044</td><td></td></tr><tr><td>Blades for scalpel handle</td><td>Fine Science Tools</td><td>10011-00</td><td></td></tr><tr><td>Bovine Serum Albumin (BSA)</td><td>NZYTech</td><td>MB04602</td><td>5% BSA is used to dilute the primary antibodies. Add 0.5g BSA in 10 mL PBS.</td></tr><tr><td>Brain/Tissue Slice Chamber System</td><td>Warner Instruments</td><td></td><td></td></tr><tr><td>Calcium chloride dihydrate</td><td>Merck Millipore</td><td>1.02382.0500</td><td></td></tr><tr><td>Cell culture inserts, 30 mm, hydrophilic PTFE</td><td>Millipore SAS</td><td>PICM03050</td><td></td></tr><tr><td>Cold light source</td><td>SCHOTT</td><td>KL 300 LED</td><td></td></tr><tr><td>Confocal laser microscope</td><td>Zeiss</td><td>LSM 710</td><td></td></tr><tr><td>Conventional incubator</td><td>Thermo Scientific Heraeus</td><td>BB15, Function Line</td><td>Set to 37 &amp;deg;C and 5% CO&lt;sub&gt;2&lt;/sub&gt;</td></tr><tr><td>D(+)-Glucose monohydrate</td><td>Merck Millipore</td><td>1.08342.1000</td><td></td></tr><tr><td>D-(+)-Glucose solution, 45% in water</td><td>Sigma</td><td>G8769</td><td></td></tr><tr><td>di-Sodium hydrogen phosphate dihydrate</td><td>Merck Milipore</td><td>1.06580.1000</td><td></td></tr><tr><td>Dissecting microscope/magnifier</td><td>MEIJI TECHNO CO. LTD</td><td>122285</td><td></td></tr><tr><td>Donkey anti-goat IgG (H+L) coupled to Alexa Fluor 568</td><td>Invitrogen</td><td>A11057</td><td>Dilute at a ratio 1:200</td></tr><tr><td>Donkey anti-mouse IgG (H+L) coupled to Alexa Fluor 488</td><td>Invitrogen</td><td>A21202</td><td>Dilute at a ratio 1:200</td></tr><tr><td>Donkey anti-mouse IgG (H+L) coupled to Alexa Fluor 568</td><td>Invitrogen</td><td>A10037</td><td>Dilute at a ratio 1:200</td></tr><tr><td>Donkey anti-rabbit IgG (H+L) coupled to Alexa Fluor 488</td><td>Invitrogen</td><td>A21206</td><td>Dilute at a ratio 1:500</td></tr><tr><td>Donkey anti-rabbit IgG (H+L) coupled to Alexa Fluor 568</td><td>Invitrogen</td><td>A10042</td><td>Dilute at a ratio 1:500</td></tr><tr><td>Dumont #5 Fine Forceps Biologie Inox</td><td>Fine Science Tools</td><td>11254-20</td><td></td></tr><tr><td>Dumont #5 Forceps Standard Inox</td><td>Fine Science Tools</td><td>11251-20</td><td></td></tr><tr><td>Dumont #7 Forceps Standard Dumoxel</td><td>Fine Science Tools</td><td>11271-30</td><td></td></tr><tr><td>Dumont Medical #7S Forceps Short Curve Inox</td><td>Fine Science Tools</td><td>11273-22</td><td></td></tr><tr><td>Gentamycin stock solution, 50 mg/mL</td><td>Thermo Fisher Scientific</td><td>15750-037</td><td></td></tr><tr><td>Gey&amp;rsquo;s Balanced Salt Solution (GBSS)</td><td>Biological Industries</td><td>01-919-1A</td><td></td></tr><tr><td>Glass Electrodes</td><td>Science Products</td><td>GB150F-10</td><td>Round tips homemade</td></tr><tr><td>Glass Pasteur pipettes, 230 mm</td><td>VWR International</td><td>612-1702</td><td></td></tr><tr><td>Hank&amp;rsquo;s Balanced Salt Solution (HBSS)</td><td>Thermo Fisher Scientific</td><td>24020-091</td><td></td></tr><tr><td>Hoechst 33342</td><td>Invitrogen</td><td>H1399</td><td>Stock solution at 2 mg/mL in PBS</td></tr><tr><td>Horse Serum, Heat Inactivated (HS)</td><td>Thermo Fisher Scientific</td><td>26050-088</td><td></td></tr><tr><td>Hydrochloric acid</td><td>Merck Milipore</td><td>1.09057.1000</td><td></td></tr><tr><td>Hydrophobic Pen</td><td>Dako</td><td>S200230-2</td><td></td></tr><tr><td>INCU-Line IL10</td><td>VWR</td><td>390-0384</td><td></td></tr><tr><td>Interface chamber</td><td>Warner Instruments</td><td>BSC-HT Haas Top</td><td></td></tr><tr><td>Iris Spatula Curved</td><td>Fine Science Tools</td><td>10092-12</td><td></td></tr><tr><td>Labculture Class II Biological Safety Cabinet</td><td>HERASafe</td><td>HS 12</td><td></td></tr><tr><td>Lens Cleaning Paper</td><td>TIFFEN</td><td></td><td></td></tr><tr><td>L-Glutamine solution 200 mM (Q)</td><td>Thermo Fisher Scientific</td><td>25030-024</td><td></td></tr><tr><td>Magnesium sulfate heptahydrate</td><td>Merck Millipore</td><td>1.05886.0500</td><td></td></tr><tr><td>Micro tube 0.5 mL, PP</td><td>SARSTEDT</td><td>72,699</td><td></td></tr><tr><td>Micro tube 1.5 mL, PP</td><td>SARSTEDT</td><td>72.690.001</td><td></td></tr><tr><td>Micro tube 2.0 mL, PP</td><td>SARSTEDT</td><td>72.691</td><td></td></tr><tr><td>Micromanipulators</td><td>Sutter Instrument</td><td>MP-285</td><td></td></tr><tr><td>Miroscope Cover Glasses, 24 mm x 60 mm</td><td>Marienfeld</td><td>102242</td><td></td></tr><tr><td>Nail polish</td><td>Clich&amp;eacute;</td><td></td><td></td></tr><tr><td>Neurobasal-A Medium (NBA)</td><td>Thermo Fisher Scientific</td><td>10888-022</td><td></td></tr><tr><td>Opti-MEM&amp;reg; I Reduced-Serum Medium</td><td>Thermo Fisher Scientific</td><td>31985-047</td><td></td></tr><tr><td>Paraformaldehyde, powder</td><td>VWR Chemicals</td><td>2,87,94,295</td><td></td></tr><tr><td>Peristaltic pump</td><td>Gilson</td><td>M312</td><td></td></tr><tr><td>Phosphate saline buffer (PBS)</td><td></td><td></td><td>Homemade. PBS with 0.5% Tween-20 (PBS-T) is used to wash slices during the immunohistochemistry assay.</td></tr><tr><td>Phosphate standard solutions, PO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;3-&lt;/sup&gt; in water</td><td>BDH ARISTAR</td><td>452232C</td><td></td></tr><tr><td>Pipette set</td><td>Gilson</td><td>P2, P10, P20, P100, P200, P1000</td><td></td></tr><tr><td>Platinum 5 blades</td><td>Gillette</td><td></td><td></td></tr><tr><td>Potassium chloride</td><td>Sigma-Aldrich</td><td>P5405-250g</td><td></td></tr><tr><td>Propidium iodide (PI)</td><td>Sigma-Aldrich</td><td>P4170-25MG</td><td>Stock solution at 1 mg/mL in water.</td></tr><tr><td>Qualitative Filter Paper, Cellulose, Grade 1, 55 mm</td><td>Whatman</td><td>1001-055</td><td>Medium retention 11&amp;micro;m</td></tr><tr><td>Qualitative Filter Paper, Cellulose, Grade 1, 90 mm</td><td>Whatman</td><td>1001-090</td><td>Medium retention 11&amp;micro;m</td></tr><tr><td>Scalpel handle</td><td>Fine Science Tools</td><td>91003-12</td><td></td></tr><tr><td>Slip Tip Insulin Syringe without Needle 1 mL</td><td>SOL-M</td><td>161000</td><td></td></tr><tr><td>Sodium chloride</td><td>VWR Chemicals</td><td>27800.360</td><td></td></tr><tr><td>Sodium dihydrogen phosphate monohydrate</td><td>Merck Millipore</td><td>1.06346.1000</td><td></td></tr><tr><td>Sodium hydrogen carbonate</td><td>Merck Millipore</td><td>1.06329.1000</td><td></td></tr><tr><td>Sodium Hydroxide&amp;lrm;</td><td>Merck Milipore</td><td>535C549998</td><td></td></tr><tr><td>Stimulator</td><td>Astro Med Inc GRASS Product Group</td><td>S48 Stimulator</td><td></td></tr><tr><td>Student Scissors Straight SharpSharp 12cm</td><td>Fine Science Tools</td><td>91402-12</td><td></td></tr><tr><td>SuperFrost Plus&amp;trade; Adhesion slides</td><td>Thermo Fisher Scientific</td><td>J1800AMNZ</td><td></td></tr><tr><td>TC-Treated Sterile 60 x 15mm Tissue Culture Dish</td><td>Corning</td><td>CORN430166</td><td></td></tr><tr><td>TC-Treated Sterile 6-Wells Plates</td><td>Corning</td><td>CORN3516</td><td></td></tr><tr><td>Temperatue controller</td><td>MEDICAL SYSTEMS CORP.</td><td>TC-102</td><td></td></tr><tr><td>Tissue Chopper</td><td>The Mickle Laboratory Engineering CO. LTD.</td><td>MTC/2</td><td>Set to 350 &amp;mu;m</td></tr><tr><td>Triton X-100</td><td>BDH</td><td>14630</td><td></td></tr><tr><td>Tween-20</td><td>Sigma</td><td>P2287</td><td></td></tr></tbody></table>

a model of epileptogenesis in rhinal cortex-hippocampus organotypic slice cultures

Organotypic slice cultures have been widely used to model brain disorders and are considered excellent platforms for evaluating a drug&#8217;s neuroprotective and therapeutic potential. Organotypic slices are prepared from explanted tissue and represent a complex multicellular ex vivo environment. They preserve the three-dimensional cytoarchitecture and local environment of brain cells, maintain the neuronal connectivity and the neuron-glia reciprocal interaction. Hippocampal organotypic slices are considered suitable to explore the basic mechanisms of epileptogenesis, but clinical research and animal models of epilepsy have suggested that the rhinal cortex, composed of perirhinal and entorhinal cortices, play a relevant role in seizure generation.
Here, we describe the preparation of rhinal cortex-hippocampus organotypic slices. Recordings of spontaneous activity from the CA3 area under perfusion with complete growth medium, at physiological temperature and in the absence of pharmacological manipulations, showed that these slices depict evolving epileptic-like events throughout time in culture. Increased cell death, through propidium iodide uptake assay, and gliosis, assessed with fluorescence-coupled immunohistochemistry, was also observed. The experimental approach presented highlights the value of rhinal cortex-hippocampus organotypic slice cultures as a platform to study the dynamics and progression of epileptogenesis and to screen potential therapeutic targets for this brain pathology.

Based on previous descriptions of epileptic signal analysis in organotypic hippocampal slices, interictal epileptiform discharges are here defined as paroxysmal discharges that are clearly distinguished from background activity, with an abrupt change in polarity and occurring at low frequency (&#60;2 Hz). Paroxysmal discharges lasting more than 10 s and occurring at higher frequency (&#8805;2 Hz) are characterized as ictal epileptiform activity. If an ictal event occurs within 10 s after the previous one, these two events are considered as only one ictal event.
Rhinal cortex-hippocampus organotypic slices at 7 DIV (Figure 3A) depict mixed interictal and ictal-like activity. At 14 DIV (Figure 3B), spontaneous activity is characterized by ictal discharges, which evolve to an overwhelming ictal activity at 21 DIV, with ictal events lasting &#62;1 min (Figure 3C).
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61330/61330fig03.jpg" /> 
Figure 3: Spontaneous epileptiform activity of rhinal cortex-hippocampus organotypic slices.&#160;Representative electrographic seizure-like events, recorded from CA3 area in an interface-type chamber, after (A) 7 DIV, (B) 14 DIV and (C) 21 DIV. Seizure details are shown in lower traces. <a href="https://www.jove.com/files/ftp_upload/61330/61330fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
PI uptake assay followed by immunohistochemistry against the neuronal marker NeuN aimed at identifying neuronal death. PI uptake by granular and pyramidal neurons was observed in 7 DIV slices (arrows in Figure 4A), but the number of PI+ neurons increased at 14 DIV (arrows in Figure 4B), corroborating an increased neuronal death with epileptogenesis progression.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/61330/61330fig04.jpg" /> 
Figure 4: Representative images of NeuN and PI stained rhinal cortex-hippocampus organotypic slices.&#160;Images of NeuN stained mature neurons and PI-positive cells were acquired at (A) 7 DIV and (B) 14 DIV, on a confocal laser microscope with a 20x objective. Magnified images of the dashed areas are shown. Arrows point to death neurons (in orange). Scale-bar, 50 &#956;m. <a href="https://www.jove.com/files/ftp_upload/61330/61330fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
A double staining of Iba1, together with CD68, was used to evaluate&#160;microglia phenotype. Iba1 is a microglia/macrophages marker, while CD68 is a lysosomal protein expressed in high levels by reactive microglia and in low levels by resting microglia. At 7 DIV slices, ramified microglia with a low CD68 expression (arrows in Figure 5A) are more abundant than Iba1+/CD68+ reactive microglia (arrowheads in Figure 5A), whereas at 14 DIV, in all areas of the hippocampus, Iba1+/CD68+ bushy/amoeboid M1 microglia (arrowheads in Figure 5B) exceed microglia with a low CD68 expression (arrows in Figure 5B). At 14 DIV some Iba1+/CD68+ cells with a hyper-ramification appearance can be pinpointed (open arrowheads&#160;in Figure 5B), which might suggest the occurrence of the M2 anti-inflammatory phenotype of microglia. However, this matter requires further study.
Recent studies demonstrated that different initiating CNS injuries can elicit at least two types of reactive astrocytes, A1 and A2, with A1 astrocytes being neurotoxic16. A1 subtype of astrocytes is characterized by an increased expression of Complement C316,17,18. Complement C3, which plays a central role in the activation of the complement system, generates C3b, which is further degraded to iC3b, C3dg and C3d19. Thus, a double staining of GFAP and C3d was employed to assess astrogliosis. At 7 DIV the expression of C3d is barely detectable (Figure 6A), while in 14 DIV slices hypertrophic GFAP+/C3d+ astrocytes can be observed (arrowheads in Figure 6B), suggesting a progressive activation of A1 astrocytes.
Results demonstrate a progressive activation of microglia and astrocytes throughout the course of epileptogenesis, mimicking the events described in patients with epilepsy and in animal models of this pathology.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/61330/61330fig5v2.jpg" /> 
Figure 5: Representative images of Iba1 and CD68 stained rhinal cortex-hippocampus organotypic slices.&#160;Images of Iba1 and CD68 stained microglia, and Hoechst stained nuclei, were acquired at (A) 7 DIV and (B) 14 DIV, on a confocal laser microscope with a 20x objective. Magnified images of the dashed areas are shown. Arrows point to Iba1+/CD68-&#160;resting microglia, arrowheads indicate Iba1+/CD68+ bushy/amoeboid&#160;microglia and open arrowheads reveal Iba1+/CD68+ hyper-ramified microglia. Scale-bar, 50 &#956;m. <a href="https://www.jove.com/files/ftp_upload/61330/61330fig5v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/61330/61330fig06.jpg" /> 
Figure 6: Representative images of GFAP and C3d stained rhinal cortex-hippocampus organotypic slices.&#160;Images of GFAP and C3d stained astrocytes, and Hoechst stained nuclei, were acquired at (A) 7 DIV and (B) 14 DIV, on a confocal laser microscope with a 20x objective. Magnified images of the dashed areas are shown. Arrowheads point to GFAP+/C3d+ reactive A1 astrocytes (in yellow). Scale-bar, 50 &#956;m. <a href="https://www.jove.com/files/ftp_upload/61330/61330fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about A Model of Epileptogenesis in Rhinal Cortex-Hippocampus Organotypic Slice Cultures at JoVE.com

A Model of Epileptogenesis in Rhinal Cortex-Hippocampus Organotypic Slice Cultures

Here, we describe the preparation of rhinal cortex-hippocampus organotypic slices. Under a gradual and controlled deprivation of serum, these slices depict evolving epileptic-like events and can be considered an ex vivo model of epileptogenesis. This system represents an excellent tool for monitoring the dynamics of spontaneous activity, as well as for assessing the progression of neuroinflammatory features throughout the course of epileptogenesis.

Organotypic slice cultures have been widely used to model brain disorders and are considered excellent platforms for evaluating a drug&#8217;s ...

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6.8K Views.  Faculdade de Medicina da Universidade de Lisboa. Here, we describe the preparation of rhinal cortex-hippocampus organotypic slices. Under a gradual and controlled deprivation of serum, these slices depict evolving epileptic-like events and can be considered an ex vivo model of epileptogenesis. This system represents an excellent tool for monitoring the dynamics of spontaneous activity, as well as for assessing the progression of neuroinflammatory features throughout the course of epileptogenesis.

Video: A Model of Epileptogenesis in Rhinal Cortex-Hippocampus Organotypic Slice Cultures

Organotypic Slice Cultures for Studies of Postnatal Neurogenesis

Here we describe a technique for studying hippocampal postnatal neurogenesis in the rodent brain using the organotypic slice culture technique. This method maintains the characteristic topographical morphology of the hippocampus while allowing direct application of pharmacological agents to the developing hippocampal dentate gyrus. Additionally, slice cultures can be maintained for up to 4 weeks and thus, allow one to study the maturation process of newborn granule neurons. Slice cultures allow for efficient pharmacological manipulation of hippocampal slices while excluding complex variables such as uncertainties related to the deep anatomic location of the hippocampus as well as the blood brain barrier. For these reasons, we sought to optimize organotypic slice cultures specifically for postnatal neurogenesis research.

Here we describe a technique for studying hippocampal postnatal neurogenesis using the organotypic slice culture technique. This method allows for in vitro manipulation of adult neurogenesis and allows for the direct application of pharmacological agents to the cultured hippocampus.

Here we describe a technique for studying hippocampal postnatal neurogenesis in the rodent brain using the organotypic slice culture technique. This ...

Developmental Biology

The Organotypic Hippocampal Slice Culture Model for Examining Neuronal Injury

Organotypic hippocampal slice culture is an in vitro method to examine mechanisms of neuronal injury in which the basic architecture and composition of the hippocampus is relatively preserved 1. The organotypic culture system allows for the examination of neuronal, astrocytic and microglial effects, but as an ex vivo preparation, does not address effects of blood flow, or recruitment of peripheral inflammatory cells. To that end, this culture method is frequently used to examine excitotoxic and hypoxic injury to pyramidal neurons of the hippocampus, but has also been used to examine the inflammatory response. Herein we describe the methods for generating hippocampal slice cultures from postnatal rodent brain, administering toxic stimuli to induce neuronal injury, and assaying and quantifying hippocampal neuronal death.

The organoptypic hippocampal slice culture model is an in vitro model used to examine neuronal injury in a variety of paradigms. In this article, we describe the methods for generating slice cultures and quantifying neuronal injury.

Organotypic hippocampal slice culture is an in vitro method to examine mechanisms of neuronal injury in which the basic architecture and composition of ...

Organotypic Hippocampal Slice Cultures

The hippocampus, a component of the limbic system, plays important roles in long-term memory and spatial navigation 1. Hippocampal neurons can modify the strength of their connections after brief periods of strong activation. This phenomenon, known as long-term potentiation (LTP) can last for hours or days and has become the best candidate mechanism for learning and memory 2. In addition, the well defined anatomy and connectivity of the hippocampus 3 has made it a classical model system to study synaptic transmission and synaptic plasticity4.
As our understanding of the physiology of hippocampal synapses grew and molecular players became identified, a need to manipulate synaptic proteins became imperative. Organotypic hippocampal cultures offer the possibility for easy gene manipulation and precise pharmacological intervention but maintain synaptic organization that is critical to understanding synapse function in a more naturalistic context than routine culture dissociated neurons methods.
Here we present a method to prepare and culture hippocampal slices that can be easily adapted to other brain regions. This method allows easy access to the slices for genetic manipulation using different approaches like viral infection 5,6 or biolistics 7. In addition, slices can be easily recovered for biochemical assays 8, or transferred to microscopes for imaging 9 or electrophysiological experiments 10.

We describe a method to prepare organotypic hippocampal slices that can be easily adapted to other brain regions. Brain slices are laid on porous membranes and culture media is allowed to form an interface. This method preserves the gross architecture of the hippocampus for up to 2 weeks in culture.

The hippocampus, a component of the limbic system, plays important roles in long-term memory and spatial navigation 1. Hippocampal neurons can modify the ...

The Analysis of Neurovascular Remodeling in Entorhino-hippocampal Organotypic Slice Cultures

Ischemic brain injury is among the most common and devastating conditions compromising proper brain function and often leads to persisting functional deficits in the affected patients. Despite intensive research efforts, there is still no effective treatment option available that reduces neuronal injury and protects neurons in the ischemic areas from delayed secondary death. Research in this area typically involves the use of elaborate and problematic animal models. Entorhino-hippocampal organotypic slice cultures challenged with oxygen and glucose deprivation (OGD) are established in&#160;vitro models which mimic cerebral ischemia. The novel aspect of this study is that changes of the brain blood vessels are studied in addition to neuronal changes and the reaction of both the neuronal compartment and the vascular compartment can be compared and correlated. The methods presented in this protocol substantially broaden the potential applications of the organotypic slice culture approach. The induction of OGD or hypoxia alone can be applied by rather simple means in organotypic slice cultures and leads to reliable and reproducible damage in the neural tissue. This is in stark contrast to the complicated and problematic animal experiments inducing stroke and ischemia in vivo. By broadening the analysis to include the study of the reaction of the vasculature could provide new ways on how to preserve and restore brain functions. The slice culture approach presented here might develop into an attractive and important tool for the study of ischemic brain injury and might be useful for testing potential therapeutic measures aimed at neuroprotection.

A protocol for entorhino-hippocampal organotypic slice cultures, which allows reproducing many aspects of ischemic brain injury, is presented. By studying changes of the neurovasculature in addition to changes in the neurons, this protocol is a versatile tool to study plastic changes in neural tissue after injury.

Ischemic brain injury is among the most common and devastating conditions compromising proper brain function and often leads to persisting functional ...

Organotypic Hippocampal Slice Cultures As a Model to Study Neuroprotection and Invasiveness of Tumor Cells

In organotypic hippocampal slice cultures (OHSC), the morphological and functional characteristics of both neurons and glial cells are well preserved. This model is suitable for addressing different research questions that involve studies on neuroprotection, electrophysiological experiments on neurons, neuronal networks or tumor invasion. The hippocampal architecture and neuronal activity in multisynaptic circuits are well conserved in OHSC, even though the slicing procedure itself initially lesions and leads to formation of a glial scar. The scar formation alters presumably the mechanical properties and diffusive behavior of small molecules, etc. Slices allow the monitoring of time dependent processes after brain injury without animal surgery, and studies on interactions between various brain-derived cell types, namely astrocytes, microglia and neurons under both physiological and pathological conditions. An ambivalent aspect of this model is the absence of blood flow and immune blood cells. During the progression of the neuronal injury, migrating immune cells from the blood play an important role. As those cells are missing in slices, the intrinsic processes in the culture may be observed without external interference. Moreover, in OHSC the composition of the medium-external environment is precisely controlled. A further advantage of this method is the lower number of sacrificed animals compared to standard preparations. Several OHSC can be obtained from one animal making simultaneous studies with multiple treatments in one animal possible. For these reasons, OHSC are well suited to analyze the effects of new protective therapeutics after tissue damage or during tumor invasion. 
The protocol presented here describes a preparation method of OHSC that allows generating highly reproducible, well preserved slices that can be used for a variety of experimental research, like neuroprotection or tumor invasion studies.

Organotypic hippocampal slice cultures (OHSC) represent an in vitro model that simulates the in vivo situation very well. Here we describe a vibratome-based improved slicing protocol to obtain high quality slices for use in assessing the neuroprotective potential of novel substances or the biological behavior of tumor cells.

In organotypic hippocampal slice cultures (OHSC), the morphological and functional characteristics of both neurons and glial cells are well preserved. ...

Preparing Acute Brain Slices from the Dorsal Pole of the Hippocampus from Adult Rodents

Whole-cell patch-clamp recordings from acute rodent brain slices are a mainstay of modern neurophysiological research, allowing precise measurement of cellular and synaptic properties. Nevertheless, there is an ever increasing need to perform correlated analyses between different experimental modes in addition to slice electrophysiology, for example: immunohistochemistry, molecular biology, in vivo imaging or electrophysiological recording; to answer evermore complex questions of brain function. However, making meaningful conclusions from these various experimental approaches is not straightforward, as even within relatively well described brain structures, a high degree of sub-regional variation of cellular function exists. Nowhere is this better exemplified than in the CA1 of the hippocampus, which has well-defined dorso-ventral properties, based on cellular and molecular properties. Nevertheless, many published studies examine protein expression patterns or behaviorally correlated in vivo activity in the dorsal extent of the hippocampus; and explain findings mechanistically with cellular electrophysiology from the ventro-medial region. This is further confounded by the fact that many acute slice electrophysiological experiments are performed in juvenile animals, when other experimental modes are performed in more mature animals. To address these issues, this method incorporates transcardial perfusion of mature (&#62;60 day old rodents) with artificial cerebrospinal fluid followed by preparation of modified coronal slices including the septal pole of the dorsal hippocampus to record from CA1 pyramidal cells. This process leads to the generation of healthy acute slices of dorsal hippocampus allowing for slice-based cellular electrophysiological interrogation matched to other measures.

The purpose of this protocol is to describe a method to produce slices of the dorsal hippocampus for electrophysiological examination. This procedure employs perfusion with chilled ACSF prior to slice preparation with a near-coronal slicing angle which allows for preservation of healthy principal neurons.

Whole-cell patch-clamp recordings from acute rodent brain slices are a mainstay of modern neurophysiological research, allowing precise measurement of ...

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 ...

Horizontal Hippocampal Slices of the Mouse Brain

The hippocampus is a highly organized structure in the brain that is a part of the limbic system and is involved in memory formation and consolidation as well as the manifestation of severe brain disorders, including Alzheimer&#8217;s disease and epilepsy. The hippocampus receives a high degree of intra- and inter-connectivity, securing a proper communication with internal and external brain structures. This connectivity is accomplished via different informational flows in the form of fiber pathways. Brain slices are a frequently used methodology when exploring neurophysiological functions of the hippocampus. Hippocampal brain slices can be used for several different applications, including electrophysiological recordings, light microscopic measurements as well as several molecular biological and histochemical techniques. Therefore, brain slices represent an ideal model system to assess protein functions, to investigate pathophysiological processes involved in neurological disorders as well as for drug discovery purposes.
There exist several different ways of slice preparations. Brain slice preparations with a vibratome allow a better preservation of the tissue structure and guarantee a sufficient oxygen supply during slicing, which present advantages over the traditional use of a tissue chopper. Moreover, different cutting planes can be applied for vibratome brain slice preparations. Here, a detailed protocol for a successful preparation of vibratome-cut horizontal hippocampal slices of mouse brains is provided. In contrast to other slice preparations, horizontal slicing allows to keep the fibers of the hippocampal input path (perforant path) in a fully intact state within a slice, which facilitates the investigation of entorhinal-hippocampal interactions. Here, we provide a thorough protocol for the dissection, extraction, and acute horizontal slicing of the murine brain, and discuss challenges and potential pitfalls of this technique. Finally, we will show some examples for the use of brain slices in further applications.

This article aims to describe a systematic protocol to obtain horizontal hippocampal brain slices in mice. The objective of this methodology is to preserve the integrity of hippocampal fiber pathways, such as the perforant path and the mossy fiber tract to assess dentate gyrus related neurological processes.

The hippocampus is a highly organized structure in the brain that is a part of the limbic system and is involved in memory formation and consolidation as ...

Preparation of Organotypic Slice Cultures from a Rat Pup&#39;s Hippocampus

Source: Mosa, A. J. et al., <a href="https://app.jove.com/v/52353">Organotypic Slice Cultures for Studies of Postnatal Neurogenesis.</a> J. Vis. Exp. (2015).
This video demonstrates a method for preparing organotypic hippocampal slice cultures from the brain of a rat pup. It outlines the steps involved in the dissection of the hippocampus, slicing, and culture conditions required to promote cell viability and growth in the hippocampal slices, ultimately generating organotypic slice cultures.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
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Neuronal Culture Techniques

Advanced Neuronal Models

Electroencephalography-Based Recording Technique to Record the Epileptiform Activity

Source: Carvalho, M. et al., <a href="https://app.jove.com/v/61330">A Model of Epileptogenesis in Rhinal Cortex-Hippocampus Organotypic Slice Cultures.</a> J. Vis. Exp. (2021).
This video describes the technique for recording the epileptiform activity of rhinal cortex-hippocampus organotypic slices ex vivo using electrophysiology or EEG set-up. This helps to study the dynamics and progression of epileptogenesis and screen potential therapeutic targets to treat epilepsy.

Source: Carvalho, M. et al., A Model of Epileptogenesis in Rhinal Cortex-Hippocampus Organotypic Slice Cultures. J. Vis. Exp. (2021).
This video describes ...