Name: preparation of rhythmically-active in vitro neonatal rodent brainstem-spinal cord and thin slice
Uploaded: 2019-03-23T13:00:00
Description: Watch this Scientific Journal Video about Preparation of Rhythmically-active In Vitro Neonatal Rodent Brainstem-spinal Cord and Thin Slice at JoVE.com

S.B.P is a recipient of a Loma Linda University Summer Undergraduate Research Fellowship.

The following protocol has been accepted and approved by the Institutional Animal Care and Use Committee (IACUC) of Loma Linda University. NIH guidelines for the ethical treatment of animals are followed in all animal experiments performed in the laboratory. All ethical standards were upheld by individuals performing this protocol.
1. Solutions
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	<li>Prepare artificial cerebral spinal fluid (aCSF).
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		<li>Prepare fresh aCSF the evening before an experiment in 1 L ba...

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Adapting the protocol presented here into an en bloc or slice workflow is advantageous for laboratories and studies that would like to utilize either en bloc brainstem-spinal cord and/or thin slice preparations for electrophysiology recordings. The dissection and slice method presented, combined with methods previously reported by others17,18,19, will allow reproducible preparation of robust and viable tissue that is widely adap...

The respiratory neural network of the brainstem provides a fertile domain for understanding the general characteristics of rhythmic neural networks. In particular, the interest is in the development of neonatal rodent breathing and understanding how the breathing rhythm develops. This may be done using a multi-level approach, including in vivo whole animal plethysmography, in vitro en bloc nerve recordings, and in vitro slice recordings that contain the breathing rhythm generator. Reductionist in vitro en bloc and slice recordings are an advantageous method to use when interrogating the mechanisms behind respiratory rhythmogenesis and neural circuitry in the brainstem-spinal cord region of developing rodents. The developing respiratory system includes approximately 40 cell types, characterized by firing pattern, including those of the central respiratory1,2. The central respiratory network includes a group of rhythmically active neurons located in the rostral ventrolateral medulla1,3. Mammalian respiratory rhythmogenesis is generated from an autorhythmic interneuron network dubbed the preB&#246;tzinger complex (pBC), which has been localized experimentally via both slice and en bloc preparations of neonatal mammalian brainstem-spinal cords3,4,5,6,7,8. This region serves a similar function to the sinoatrial node (SA) in the heart and generates an inspiratory timing system to drive respiration. From the pBC, the inspiratory rhythm is carried to other regions of the brainstem (including the hypoglossal motor nucleus) and spinal motor pools (such as the phrenic motor neurons that drive the diaphragm)9.
Rhythmic activity may be obtained using brainstem spinal cord en bloc preparations or slices from a variety of cell populations, including C3-C5 nerve rootlets, XII nerve rootlets, hypoglossal motor nucleus (XII MN), hypoglossal premotor neurons (XII pMN), and the pBC3,10,11,12. While these methods of data collection have been successful across a handful of laboratories, many of the protocols are not presented in a way that is fully reproducible for new researchers entering the field. Obtaining viable and rhythmically active en bloc and slice preparations requires an acute attention to detail through all steps of the dissection and slice cutting protocol. Previous protocols extensively describe the various recording procedures and electrophysiology, yet lack detail in the most critical part of obtaining a viable tissue preparation: performing the brainstem-spinal cord dissection and slice procedure.
Efficiently obtaining a rhythmically-active and viable en bloc or slice preparation brainstem-spinal cord electrophysiology recordings requires that all steps be performed correctly, carefully, and swiftly (typically, the whole procedure related here can be performed in approximately 30 min). Critical points of the brainstem-spinal cord electrophysiology protocol that have not been previously well described include the dissection of nerve rootlets and the slicing procedure on the vibratome. This protocol is the first to stepwise visually communicate the brainstem-spinal cord dissection for both new researchers and experts in the field. This protocol also thoroughly explains surgical techniques, landmarks, and other procedures to assist future researchers in standardizing slices and en bloc preparations to contain the exact circuitry desired in each experiment. The procedures presented here can be used in both rat and mouse neonatal pups.

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			<td style="width:320px;">S271-500</td>
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			<td>Sigma Aldrich</td>
			<td>P5405-1KG</td>
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			<td>Fisher Scientific</td>
			<td>BP328-1</td>
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			<td>S9638-25G</td>
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			<td>Sigma Aldrich</td>
			<td>G8270-1KG</td>
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			<td>AmScope</td>
			<td>H2L50-AY</td>
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			<td height="21" style="height:21px;">Dissection Microscope</td>
			<td>Leica</td>
			<td>M-60</td>
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			<td height="21" style="height:21px;">Vibratome 1000 Plus</td>
			<td>Vibratome</td>
			<td>W3 69-0353</td>
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			<td height="21" style="height:21px;">Magnetic Base</td>
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			<td>MB-B-DG6C</td>
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			<td height="21" style="height:21px;">Isoflurane, USP</td>
			<td>Patterson Veterinary</td>
			<td>NDC 14043-704-06</td>
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			<td height="21" style="height:21px;">Sword Classic Double Edge Blades</td>
			<td>Wilkinson</td>
			<td>97573</td>
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			<td>H2779</td>
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			<td height="21" style="height:21px;">Dumont #5 Fine Forceps</td>
			<td>Fine Science Tools</td>
			<td>11254-20</td>
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			<td>11251-35</td>
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			<td>10010-00</td>
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			<td height="21" style="height:21px;">Scalpel Handel #3</td>
			<td>Fine Science Tools</td>
			<td>10003-12</td>
			<td></td>
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			<td height="21" style="height:21px;">Spring Scissors Straight&#160;</td>
			<td>Fine Science Tools</td>
			<td>15024-10</td>
			<td></td>
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			<td height="21" style="height:21px;">Narrow Pattern Forcep Serrated/straight</td>
			<td>Fine Science Tools</td>
			<td>11002-12</td>
			<td></td>
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			<td height="21" style="height:21px;">Castroviejo Micro Dissecting Spring Scissors; Straight</td>
			<td>Roboz</td>
			<td>RS-5650</td>
			<td></td>
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			<td height="21" style="height:21px;">Vannas Scissors 3&#34; Curved</td>
			<td>Roboz</td>
			<td>RS-5621</td>
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			<td>Fine Science Tools/8840604</td>
			<td>26000-35&#160;</td>
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			<td>Fine Science Tools</td>
			<td>26001-35</td>
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			<td height="21" style="height:21px;">Insect pins, 000</td>
			<td>Fine Science Tools</td>
			<td>26000-25</td>
			<td></td>
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			<td height="21" style="height:21px;">Insect pins, 000, SS</td>
			<td>Fine Science Tools</td>
			<td>26001-25</td>
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			<td height="21" style="height:21px;">Minutien pins, 0.10 mm</td>
			<td>Fine Science Tools</td>
			<td>26002-10</td>
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			<td height="21" style="height:21px;">Minutien pins, 0.15 mm</td>
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			<td>26002-15</td>
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			<td height="21" style="height:21px;">Minutien pins, 0.2 mm</td>
			<td>Fine Science Tools</td>
			<td>26002-20</td>
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			<td height="21" style="height:21px;">Fisher Tissue prep Parafin&#160;</td>
			<td>fisher</td>
			<td>T56-5</td>
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			<td>Grainger</td>
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			<td>BD</td>
			<td>305195</td>
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preparation of rhythmically-active in vitro neonatal rodent brainstem-spinal cord and thin slice

Mammalian inspiratory rhythm is generated from a neuronal network in a region of the medulla called the preB&#246;tzinger complex (pBC), which produces a signal driving the rhythmic contraction of inspiratory muscles. Rhythmic neural activity generated in the pBC and carried to other neuronal pools to drive the musculature of breathing may be studied using various approaches, including en bloc nerve recordings and transverse slice recordings. However, previously published methods have not extensively described the brainstem-spinal cord dissection process in a transparent and reproducible manner for future studies. Here, we present a comprehensive overview of a method used to reproducibly cut rhythmically-active brainstem slices containing the necessary and sufficient neuronal circuitry for generating and transmitting inspiratory drive. This work builds upon previous brainstem-spinal cord electrophysiology protocols to enhance the likelihood of reliably obtaining viable and rhythmically-active slices for recording neuronal output from the pBC, hypoglossal premotor neurons (XII pMN), and hypoglossal motor neurons (XII MN). The work presented expands upon previous published methods by providing detailed, step-by-step illustrations of the dissection, from whole rat pup, to in vitro slice containing the XII rootlets.

The method presented here allows a researcher interested in obtaining rhythmically active slices of brainstem to reproducibly and reliably cut a viable, robust slice that will allow recording of fictive motor output for many hours. All of the minimally necessary neural circuit elements for generating and transmitting inspiratory rhythm can be captured in a thin slice using this method. These elements include: the preB&#246;tzinger Complex, premotor neurons projecting to the hypoglossal mo...

Watch this Scientific Journal Video about Preparation of Rhythmically-active In Vitro Neonatal Rodent Brainstem-spinal Cord and Thin Slice at JoVE.com

Preparation of Rhythmically-active In Vitro Neonatal Rodent Brainstem-spinal Cord and Thin Slice

This protocol both visually communicates the brainstem-spinal cord preparation and clarifies the preparation of brainstem transverse slices in a comprehensive step-by-step manner. It was designed to increase reproducibility and enhance the likelihood of obtaining viable, long lasting, rhythmically-active slices for recording neural output from the respiratory regions of the brainstem.

Mammalian inspiratory rhythm is generated from a neuronal network in a region of the medulla called the preB&#246;tzinger complex (pBC), which produces a ...

This method facilitates the reproducible dissection and slicing of rodent brainstems for the captured analysis of the Mirian Medullary Respiratory Network. This technique offers great experimental flexibility, making it possible to prepare either an in-vitro unblock or a slice preparation for recording. This method may be used for electrophysiology experiments to explore the neural control circuit that generates breathing rhythms and to understand the pathology and disregulation of breathing in genetically modified rodents.After dissection of the neuraxis, quickly transfer the isolated trunk of the animal to an aerated dissection chamber under a dissection microscope and place the tissue dorsal-side up, with the rostral end facing the front of the chamber. Pin the tissue at the shoulders and the most caudal end of the spinal cord and make a midsagittal incision through the skull following the parietal suture to avoid damaging the cortex and the brainstem underlying the skull. Beginning at the sagittal suture and working laterally, snip the occipital sutures of the skull to create flaps of bone that may be reflected and pinned to anchor and stabilize the rostral part of the skull.After reflecting both skull flaps, excise the remainder of the cerebral cortex, leaving the caudal portion of the cerebellum relatively intact to perform a dorsal laminectomy. Use micro spring scissors and forceps to remove the musculature surrounding the skull and vertebral column. Remove the tissue along the dorsal side of the ribcage, leaving the ribs intact and carefully snip away the lateral processes of the vertebral lamina.After cutting away any tissue overlying the pons and medulla, the vermis, cerebellum, pons and beginning of the spinal cord, will be clearly visible. To perform a ventral laminectomy, place the tissue dorsal-side down and pin at the ribcage and the most caudal end of the spine. Use the skull flaps to pin down the rostral-side of the tissue and remove the ventral half of the ribcage, including the sternum and all of the abdominal organs.Dissect away the soft tissue attached to the ribcage to expose the ribs and spinal cord and remove the tongue, esophagus, trachea, larynx and all of the other soft tissue and musculature overlying the base of the skull and the spinal column. In order to identify the hard pallet, dissect the tissue overlying this rectangular plate of bone at the base of the skull, that includes a v-shape indentation. Then cut along the midline of the pallet, carefully lifting the tissue upwards and perform a transverse cut to remove it.To begin a ventral laminectomy, remove the lamina, exposing the ventral surface of the brainstem and the spinal cord from the first cervical vertebra to approximately the thoracic vertebra seven and snip five to 10 millimeters along both sides of the spinal column at the lamina. When the spinal cord has been exposed, snip the rootlets approximately 20 to 25 millimeters bilaterally, along the spinal column to approximately T7 and carefully lift the rostral edge of C1, C2 and C3 with hooked or bent forceps to allow snipping beneath the bone for removal of the three vertebra. When the desired length of spinal cord has been isolated from the vertebral column, make a transverse cut to remove the spinal cord tissue.After removing the dura, place the brainstem in the center of the paraffin platform on the plastic cutting block and use fine insect pins, trimmed to no more than one centimeter in length to pin the caudal end of the brainstem through the distal spinal cord. Then align the paraffin covered cutting block with the pinned brainstem in the Vibratone block holder, so that the blade will cut perpendicular to the rostral face of the brainstem. Next, make an initial slice to remove 200 to 300 micrometers of uneven extraneous tissue on the rostral-most end of the tissue, making small adjustments as necessary to ensure PARP linearity and small cuts to remove any uneven tissue.The glossopharyngeal rootlets will become visible at the lateral edge of the brainstem, cut a 300 to 500 micrometer slice of brainstem from these rostral neuroanatomical markers to capture the pre-Botzinger complex and the associated transmission circuitry. All of the slicing procedure steps are critical for creating a reproducible, viable slice, with all of the necessary neuronal circuitry in the correct orientation to produce robust rhythm. All of the minimally necessary neural circuit elements for generating and transmitting inspiratory rhythm can be captured in a thin slice using this method.Including the pre-Botzinger complex, pre-motor neurons projecting to the hypoglossal motor neurons and the hypoglossal nerve rootlets. The pre-Botzinger complex, the hypoglossal or 12th cranial nerve rootlets and C4 nerve rootlets can then be used for inspiratory recording. The key aspect of this procedure is the careful isolation of the rootlets and confirmation that the brainstem is not damaged before cutting the final slice.Following this procedure, electrophysiology recordings can be made using patch clamp methods, extra cellular recordings or suction electrodes to record the electrical activity produced by the network. Previously published protocols have provided little step-by-step detail, making it difficult for new researchers to use this method without traveling to another laboratory and spending time with a seasoned investigator.

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Research

JoVE Journal

Neuroscience

Whole Cell Recording from an Organotypic Slice Preparation of Neocortex

We have been studying the expression and functional roles of voltage-gated potassium channels in pyramidal neurons from rat neocortex. Because of the lack of specific pharmacological agents for these channels, we have taken a genetic approach to manipulating channel expression. We use an organotypic culture preparation (16) in order to maintain cell morphology and the laminar pattern of cortex. We typically isolate acute neocortical slices at postnatal days 8-10 and maintain the slices in culture for 3-7 days. This allows us to study neurons at a similar age to those in our work with acute slices and minimizes the development of exuberant excitatory connections in the slice. We record from visually-identified pyramidal neurons in layers II/III or V using infrared illumination (IR-) and differential interference contrast microscopy (DIC) with whole cell patch clamp in current- or voltage-clamp. We use biolistic (Gene gun) transfection of wild type or mutant potassium channel DNA to manipulate expression of the channels to study their function. The transfected cells are easily identified by epifluorescence microscopy after co-transfection with cDNA for green fluorescent protein (GFP). We compare recordings of transfected cells to adjacent, untransfected neurons in the same layer from the same slice.

This is a protocol to prepare and maintain a neocortical slice preparation in organotypic culture for the purpose of making electrical recordings from pyramidal neurons.

We have been studying the expression and functional roles of voltage-gated potassium channels in pyramidal neurons from rat neocortex.  Because of the ...

Imaging Pheromone Sensing in a Mouse Vomeronasal Acute Tissue Slice Preparation

Peter Karlson and Martin L&uuml;scher used the term pheromone for the first time in 19591 to describe chemicals used for intra-species communication. Pheromones are volatile or non-volatile short-lived molecules2 secreted and/or contained in biological fluids3,4, such as urine, a liquid known to be a main source of pheromones3. Pheromonal communication is implicated in a variety of key animal modalities such as kin interactions5,6, hierarchical organisations3 and sexual interactions7,8 and are consequently directly correlated with the survival of a given species9,10,11. In mice, the ability to detect pheromones is principally mediated by the vomeronasal organ (VNO)10,12, a paired structure located at the base of the nasal cavity, and enclosed in a cartilaginous capsule. Each VNO has a tubular shape with a lumen13,14 allowing the contact with the external chemical world. The sensory neuroepithelium is principally composed of vomeronasal bipolar sensory neurons (VSNs)15. Each VSN extends a single dendrite to the lumen ending in a large dendritic knob bearing up to 100 microvilli implicated in chemical detection16. Numerous subpopulations of VSNs are present. They are differentiated by the chemoreceptor they express and thus possibly by the ligand(s) they recognize17,18. Two main vomeronasal receptor families, V1Rs and V2Rs19,20,21,22, are composed respectively by 24023 and 12024 members and are expressed in separate layers of the neuroepithelium. Olfactory receptors (ORs)25 and formyl peptide receptors (FPRs)26,27 are also expressed in VSNs.
Whether or not these neuronal subpopulations use the same downstream signalling pathway for sensing pheromones is unknown. Despite a major role played by a calcium-permeable channel (TRPC2) present in the microvilli of mature neurons28 TRPC2 independent transduction channels have been suggested6,29. Due to the high number of neuronal subpopulations and the peculiar morphology of the organ, pharmacological and physiological investigations of the signalling elements present in the VNO are complex.
Here, we present an acute tissue slice preparation of the mouse VNO for performing calcium imaging investigations. This physiological approach allows observations, in the natural environment of a living tissue, of general or individual subpopulations of VSNs previously loaded with Fura-2AM, a calcium dye. This method is also convenient for studying any GFP-tagged pheromone receptor and is adaptable for the use of other fluorescent calcium probes. As an example, we use here a VG mouse line30, in which the translation of the pheromone V1rb2 receptor is linked to the expression of GFP by a polycistronic strategy.

In mice, the ability to detect pheromones is principally mediated by the vomeronasal organ (VNO). Here, an acute tissue slice preparation of VNO for performing calcium imaging is described. This physiological approach allows observations of subpopulations and/or individual neurons in a living tissue and is convenient for receptor-ligand identification.

Peter Karlson and Martin L&uuml;scher used the term pheromone for the first time in 19591 to describe chemicals used for intra-species communication. ...

Chicken Embryo Spinal Cord Slice Culture Protocol

Slice cultures can facilitate the manipulation of embryo development both pharmacologically and through gene manipulations. In this reduced system, potential lethal side effects due to systemic drug applications can be overcome. However, culture conditions must ensure that normal development proceeds within the reduced environment of the slice. We have focused on the development of the spinal cord, particularly that of spinal motor neurons. We systematically varied culture conditions of chicken embryo slices from the point at which most spinal motor neurons had been born. We assayed the number and type of motor neurons that survived during the culture period and the position of those motor neurons compared to that in vivo. We found that serum type and neurotrophic factors were required during the culture period and were able to keep motor neurons alive for at least 24 hr and allow those motor neurons to migrate to appropriate positions in the spinal cord. We present these culture conditions and the methodology of preparing the embryo slice cultures using eviscerated chicken embryos embedded in agarose and sliced using a vibratome.

Slice cultures facilitate the manipulation of embryo development by gene and pharmacological perturbations. However, culture conditions must ensure that normal development can proceed within the reduced environment of the slice. We illustrate a protocol that facilitates normal spinal cord development to proceed for at least 24 hr.

Slice cultures can facilitate the manipulation of  embryo development both pharmacologically and through gene manipulations. In  this reduced system, ...

Nucleofection of Rodent Neuroblasts to Study Neuroblast Migration In vitro

The subventricular zone (SVZ) located in the lateral wall of the lateral ventricles plays a fundamental role in adult neurogenesis. In this restricted area of the brain, neural stem cells proliferate and constantly generate neuroblasts that migrate tangentially in chains along the rostral migratory stream (RMS) to reach the olfactory bulb (OB). Once in the OB, neuroblasts switch to radial migration and then differentiate into mature neurons able to incorporate into the preexisting neuronal network. Proper neuroblast migration is a fundamental step in neurogenesis, ensuring the correct functional maturation of newborn neurons. Given the ability of SVZ-derived neuroblasts to target injured areas in the brain, investigating the intracellular mechanisms underlying their motility will not only enhance the understanding of neurogenesis but may also promote the development of neuroregenerative strategies.
This manuscript describes a detailed protocol for the transfection of primary rodent RMS postnatal neuroblasts and the analysis of their motility using a 3D in vitro migration assay recapitulating their mode of migration observed in vivo. Both rat and mouse neuroblasts can be quickly and efficiently transfected via nucleofection with either plasmid DNA, small hairpin (sh)RNA or short interfering (si)RNA oligos targeting genes of interest. To analyze migration, nucleofected cells are reaggregated in &#39;hanging drops&#39; and subsequently embedded in a three-dimensional matrix. Nucleofection per se does not significantly impair the migration of neuroblasts. Pharmacological treatment of nucleofected and reaggregated neuroblasts can also be performed to study the role of signaling pathways involved in neuroblast migration.

Nucleofection of Rodent Neuroblasts to Study Neuroblast Migration In vitro

Neuroblast migration is a crucial step in postnatal neurogenesis. The protocol described here can be used to investigate the role of candidate regulators of neuroblast migration by employing DNA/small hairpin RNA (shRNA) nucleofection and a 3D migration assay with neuroblasts isolated from the rodent postnatal rostral migratory stream.

The subventricular zone (SVZ) located in the lateral wall of the lateral ventricles plays a fundamental role in adult neurogenesis. In this restricted ...

Electrophysiology on Isolated Brainstem-spinal Cord Preparations from Newborn Rodents Allows Neural Respiratory Network Output Recording

While it is well known that the central respiratory drive is located in the brainstem, several aspects of its basic function, development, and response to stimuli remain to be fully understood. To overcome the difficulty of accessing the brainstem in the whole animal, isolation of the brainstem and part of the spinal cord is performed. This preparation is maintained in artificial cerebro-spinal fluid where gases, concentrations, and temperature are controlled and monitored. The output signal from the respiratory network is recorded by a suction electrode placed on the fourth ventral root. In this manner, stimuli can be directly applied onto the brainstem, and the effect can be recorded directly. The signal recorded is linked to the inspiratory signal sent to the diaphragm via the phrenic nerve, and can be described as bursts (around 8 bursts per minute). Analysis of these bursts (frequency, amplitude, length, and area under the curve) allows precise characterization of the stimulus effect on the respiratory network. The main limitation of this method is the viability of the preparation beyond the early post-natal stages. Thus, this method greatly focuses on the study of the whole network without the peripheral inputs in the newborn rat.

The central respiratory drive is located in the brainstem. Spontaneous respiratory motor output from an isolated brainstem-spinal cord is recorded by placing an electrode on the fourth ventral root. This experimental approach is valuable for pharmacological investigations or the assessment of respiratory challenges and genetic manipulations on rhythmic motor behavior.

While it is well known that the central respiratory drive is located in the brainstem, several aspects of its basic function, development, and response to ...

Spinal Cord Neurons Isolation and Culture from Neonatal Mice

We present a protocol for the isolation and culture of spinal cord neurons. The neurons are obtained from neonatal C57BL/6 mice and are isolated on postnatal day 1-3. A mouse litter, usually 4-10 pups born from one breeding pair, is gathered for one experiment, and spinal cords are collected individually from each mouse after euthanasia with isoflurane. The spinal column is dissected out and then the spinal cord is released from the column. The spinal cords are then minced to increase the surface area of delivery for an enzymatic protease that allows for the neurons and other cells to be released from the tissue. Trituration is then used to release the cells into solution. This solution is subsequently fractionated in a density gradient to separate the various cells in solution, allowing for neurons to be isolated. Approximately 1-2.5 x 106 neurons can be isolated from one litter group. The neurons are then seeded onto wells coated with adhesive factors that allow for proper growth and maturation. The neurons take approximately 7 days to reach maturity in the growth and culture medium and can be used thereafter for treatment and analysis.

This study presents a technique for the isolation of neurons from WT neonatal mice. It requires the careful dissection of the spinal cord from the neonatal mouse, followed by the separation of neurons from the spinal cord tissue through mechanical and enzymatic cleavage.

We present a protocol for the isolation and culture of spinal cord neurons. The neurons are obtained from neonatal C57BL/6 mice and are isolated on ...

Preparation and Immunostaining of Myelinating Organotypic Cerebellar Slice Cultures

In the nervous system, myelin is a complex membrane structure generated by myelinating glial cells, which ensheathes axons and facilitates fast electrical conduction. Myelin alteration has been shown to occur in various neurological diseases, where it is associated with functional deficits. Here, we provide a detailed description of an ex vivo model consisting of mouse organotypic cerebellar slices, which can be maintained in culture for several weeks and further be labeled to visualize myelin.

Here we present a method to prepare organotypic slice cultures from mouse cerebellum and myelin sheath staining by immunohistochemistry suitable for investigating mechanisms of myelination and remyelination in the central nervous system.

In the nervous system, myelin is a complex membrane structure generated by myelinating glial cells, which ensheathes axons and facilitates fast electrical ...

In Vitro Wedge Slice Preparation for Mimicking In Vivo Neuronal Circuit Connectivity

In vitro slice electrophysiology techniques measure single-cell activity with precise electrical and temporal resolution. Brain slices must be relatively thin to properly visualize and access neurons for patch-clamping or imaging, and in vitro examination of brain circuitry is limited to only what is physically present in the acute slice. To maintain the benefits of in vitro slice experimentation while preserving a larger portion of presynaptic nuclei, we developed a novel slice preparation. This &#8220;wedge slice&#8221; was designed for patch-clamp electrophysiology recordings to characterize the diverse monaural, sound-driven inputs to medial olivocochlear (MOC) neurons in the brainstem. These neurons receive their primary afferent excitatory and inhibitory inputs from neurons activated by stimuli in the contralateral ear and corresponding cochlear nucleus (CN). An asymmetrical brain slice was designed which is thickest in the rostro-caudal domain at the lateral edge of one hemisphere and then thins towards the lateral edge of the opposite hemisphere. This slice contains, on the thick side, the auditory nerve root conveying information about auditory stimuli to the brain, the intrinsic CN circuitry, and both the disynaptic excitatory and trisynaptic inhibitory afferent pathways that converge on contralateral MOC neurons. Recording is performed from MOC neurons on the thin side of the slice, where they are visualized using DIC optics for typical patch-clamp experiments. Direct stimulation of the auditory nerve is performed as it enters the auditory brainstem, allowing for intrinsic CN circuit activity and synaptic plasticity to occur at synapses upstream of MOC neurons. With this technique, one can mimic in vivo circuit activation as closely as possible within the slice. This wedge slice preparation is applicable to other brain circuits where circuit analyses would benefit from preservation of upstream connectivity and long-range inputs, in combination with the technical advantages of in vitro slice physiology.

Integration of diverse synaptic inputs to neurons is best measured in a preparation that preserves all pre-synaptic nuclei for natural timing and circuit plasticity, but brain slices typically sever many connections. We developed a modified brain slice to mimic in vivo circuit activity while maintaining in vitro experimentation capability.

In vitro slice electrophysiology techniques measure single-cell activity with precise electrical and temporal resolution. Brain slices must be relatively ...

Uptake of Fluorescent Labeled Small Extracellular Vesicles In Vitro and in Spinal Cord

Small extracellular vesicles (sEVs) are 50-150 nm vesicles secreted by all cells and present in bodily fluids. sEVs transfer biomolecules such as RNA, proteins, and lipids from donor to acceptor cells, making them key signaling mediators between cells. In the central nervous system (CNS), sEVs can mediate intercellular signaling, including neuroimmune interactions. sEV functions can be studied by tracking the uptake of labeled sEVs in recipient cells both in vitro and in vivo. This paper describes the labeling of sEVs from the conditioned media of RAW 264.7 macrophage cells using a PKH membrane dye. It shows the uptake of different concentrations of labeled sEVs at multiple time points by Neuro-2a cells and primary astrocytes in vitro. Also shown is the uptake of sEVs delivered intrathecally in mouse spinal cord neurons, astrocytes, and microglia visualized by confocal microscopy. The representative results demonstrate time-dependent variation in the uptake of sEVs by different cells, which can help confirm successful sEVs delivery into the spinal cord.

Uptake of Fluorescent Labeled Small Extracellular Vesicles In Vitro and in Spinal Cord

We describe a protocol to label macrophage-derived small extracellular vesicles with PKH dyes and observe their uptake in vitro and in the spinal cord after intrathecal delivery.

Small extracellular vesicles (sEVs) are 50-150 nm vesicles secreted by all cells and present in bodily fluids. sEVs transfer biomolecules such as RNA, ...

Whole Neonatal Cochlear Explants as an In vitro Model

Untreated hearing loss imposes significant costs on the global healthcare system and impairs individuals' quality of life. Sensorineural hearing loss is characterized by the cumulative and irreversible loss of sensory hair cells and auditory nerves in the cochlea. Entire and vital cochlear explants are one of the fundamental tools in hearing research to detect hair cell loss and to characterize the molecular mechanisms of the inner ear cells. Many years ago, a protocol for neonatal cochlear isolation was developed, and although it has been modified over time, it still holds potential for improvement. 
This paper presents an optimized protocol for isolating and culturing whole neonatal cochlear explants in multi-well culture chambers that enables the study of hair cells and spiral ganglion neuron cells along the entire length of the cochlea. The protocol was tested using cochlear explants from mice and rats. Healthy cochlear explants were obtained to study the interaction between hair cells, spiral ganglion neuron cells, and the surrounding supporting cells. 
One of the main advantages of this method is that it simplifies the organ culture steps without compromising the quality of the explants. All three turns of the organ of Corti are attached to the bottom of the chamber, which facilitates in vitro experiments and the comprehensive analysis of the explants. We provide some examples of cochlear images from different experiments with live and fixed explants, demonstrating that the explants retain their structure despite exposure to ototoxic drugs. This optimized protocol can be widely used for the integrative analysis of the mammalian cochlea.

Whole Neonatal Cochlear Explants as an In vitro Model

The current protocol updates previous protocols and incorporates relatively straightforward approaches for culturing high-quality cochlear explants. This provides reliable data acquisition and high-resolution imaging in live and fixed cells. This protocol supports the ongoing trend of studying inner ear cells.

Untreated hearing loss imposes significant costs on the global healthcare system and impairs individuals' quality of life. Sensorineural hearing loss is ...